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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=ISO8859-1" /><title>GNU Backgammon Manual V1.00.0</title><meta name="generator" content="DocBook XSL Stylesheets V1.78.1" /><meta name="description" content="The GNU Backgammon manual" /><link rel="home" href="#gnubg" title="GNU Backgammon Manual V1.00.0" /><link rel="next" href="#gnubg-intro" title="Introduction" /></head><body><div xml:lang="en" class="article" lang="en"><div class="titlepage"><div><div><h2 class="title"><a id="gnubg"></a><span class="application">GNU Backgammon</span> Manual
V1.00.0</h2></div><div><div class="authorgroup"><div class="author"><h3 class="author"><span class="firstname">Christian</span> <span class="surname">Anthon</span></h3><div class="affiliation"><span class="orgname">GNU Backgammon Project<br /></span><div class="address"><p><br />
<code class="email"><<a class="email" href="mailto:christian.anthon@gmail.com">christian.anthon@gmail.com</a>></code><br />
</p></div></div></div></div></div><div><p class="releaseinfo">This manual describes version 1.00.0 of GNU Backgammon. </p></div><div><p class="copyright">Copyright © 1999, 2000, 2001, 2002, 2003 Achim Mueller, Gary Wong</p></div><div><p class="copyright">Copyright © 2007 Christian Anthon</p></div><div><div class="legalnotice"><a id="idp34499808"></a><p> Permission is granted to copy, distribute and/or modify this document under the
terms of the GNU Free Documentation License, Version 1.3 or any later version
published by the Free Software Foundation; with no Invariant Sections, no
Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in
the section entitled “GNU Free Documentation License”.<a class="xref" href="#legal" title="A. GNU Free Documentation License">Appendix A, <em>GNU Free Documentation License</em></a>. </p><p class="legalnotice-title"><strong>Feedback</strong></p><p>To report a bug or make a suggestion regarding the <span class="application">GNU Backgammon</span> application or this
manual, send your suggestions to <code class="email"><<a class="email" href="mailto:bug-gnubg@gnu.org">bug-gnubg@gnu.org</a>></code> or
make a <a class="ulink" href="https://savannah.gnu.org/bugs/?group=gnubg" target="_top">bug
report</a>.</p></div></div><div><div class="revhistory"><table style="border-style:solid; width:100%;" summary="Revision History"><tr><th align="left" valign="top" colspan="2"><strong>Revision History</strong></th></tr><tr><td align="left">Revision GNU Backgammon Manual (docbook version)</td><td align="left">February 2007</td></tr><tr><td align="left" colspan="2">
<p class="publisher">GNU Backgammon Project</p>
</td></tr><tr><td align="left">Revision GNU Backgammon Manual (wiki version)</td><td align="left">January 2007</td></tr><tr><td align="left" colspan="2">
<p class="publisher">GNU Backgammon Project</p>
</td></tr><tr><td align="left">Revision GNU Backgammon Manual (texinfo version)</td><td align="left">November 2003</td></tr><tr><td align="left" colspan="2">
<p class="publisher">GNU Backgammon Project</p>
</td></tr></table></div></div><div><div class="abstract"><p class="title"><strong>Abstract</strong></p><p>The GNU Backgammon manual</p></div></div></div><hr /></div><div class="toc"><p><strong>Table of Contents</strong></p><dl class="toc"><dt><span class="sect1"><a href="#gnubg-intro">Introduction</a></span></dt><dd><dl><dt><span class="sect2"><a href="#gnubg-intro_gpl">GPL copying/warranty info</a></span></dt></dl></dd><dt><span class="sect1"><a href="#gnubg-rules">Rules of the game</a></span></dt><dd><dl><dt><span class="sect2"><a href="#gnubg-rules_setup">Setup</a></span></dt><dt><span class="sect2"><a href="#gnubg-rules_object">Object of the Game</a></span></dt><dt><span class="sect2"><a href="#gnubg-rules_movement">Movement of the Checkers</a></span></dt><dt><span class="sect2"><a href="#gnubg-rules_hitting">Hitting and Entering</a></span></dt><dt><span class="sect2"><a href="#gnubg-rules_bearingoff">Bearing Off</a></span></dt><dt><span class="sect2"><a href="#gnubg-rules_doubling">Doubling</a></span></dt><dt><span class="sect2"><a href="#gnubg-rules_gammons">Gammons and Backgammons</a></span></dt><dt><span class="sect2"><a href="#gnubg-rules_optional">Optional Rules</a></span></dt><dt><span class="sect2"><a href="#gnubg-rules_match">Rules for Match Play</a></span></dt></dl></dd><dt><span class="sect1"><a href="#gnubg-starting">Starting GNU Backgammon</a></span></dt><dd><dl><dt><span class="sect2"><a href="#gnubg-starting_unix">Linux and Unix</a></span></dt><dt><span class="sect2"><a href="#gnubg-starting_ms">Microsoft Windows</a></span></dt><dt><span class="sect2"><a href="#gnubg-starting_mac">Mac OS X</a></span></dt><dt><span class="sect2"><a href="#gnubg-starting_options">Command line options</a></span></dt></dl></dd><dt><span class="sect1"><a href="#gnubg-playing">Playing a game</a></span></dt><dd><dl><dt><span class="sect2"><a href="#gnubg-playing_new">Starting a new match or session</a></span></dt><dt><span class="sect2"><a href="#gnubg-playing_roll">Rolling the dice</a></span></dt><dt><span class="sect2"><a href="#gnubg-playing_move">Moving the checkers</a></span></dt><dt><span class="sect2"><a href="#gnubg-playing_double">Using the doubling cube</a></span></dt><dt><span class="sect2"><a href="#gnubg-playing_resign">Resigning</a></span></dt></dl></dd><dt><span class="sect1"><a href="#gnubg-hint">Getting hints and Tutor Mode</a></span></dt><dd><dl><dt><span class="sect2"><a href="#gnubg-hint_manual">Getting hints manually</a></span></dt><dt><span class="sect2"><a href="#gnubg-hint_tutor">Tutor mode</a></span></dt></dl></dd><dt><span class="sect1"><a href="#gnubg-edit">Setting up a position</a></span></dt><dd><dl><dt><span class="sect2"><a href="#gnubg-edit_entering">Entering Edit mode</a></span></dt><dt><span class="sect2"><a href="#gnubg-edit_edit">Editing</a></span></dt><dt><span class="sect2"><a href="#gnubg-edit_clear">Clearing the board</a></span></dt><dt><span class="sect2"><a href="#gnubg-edit_quick">Quick edit</a></span></dt><dt><span class="sect2"><a href="#gnubg-edit_drag">Editing by drag and drop</a></span></dt><dt><span class="sect2"><a href="#gnubg-edit_turn">Setting the player on turn</a></span></dt><dt><span class="sect2"><a href="#gnubg-edit_dice">Setting the dice</a></span></dt><dt><span class="sect2"><a href="#gnubg-edit_cube">Setting the cube</a></span></dt><dt><span class="sect2"><a href="#gnubg-edit_score">Setting the score</a></span></dt><dt><span class="sect2"><a href="#gnubg-edit_exit">Exiting Edit mode</a></span></dt><dt><span class="sect2"><a href="#gnubg-edit_analyse">Analysing the position</a></span></dt></dl></dd><dt><span class="sect1"><a href="#gnubg-matches">Working with matches</a></span></dt><dd><dl><dt><span class="sect2"><a href="#gnubg-matches_ras">Retrieving and storing backgammon files</a></span></dt><dt><span class="sect2"><a href="#gnubg-matches_entering">Entering live tournament matches</a></span></dt><dt><span class="sect2"><a href="#gnubg-matches_analysing">Analysing matches</a></span></dt><dt><span class="sect2"><a href="#gnubg-matches_review">Reviewing matches</a></span></dt></dl></dd><dt><span class="sect1"><a href="#gnubg-rollouts">Rollouts</a></span></dt><dd><dl><dt><span class="sect2"><a href="#gnubg-rollouts_intro">Introduction to rollouts</a></span></dt><dt><span class="sect2"><a href="#gnubg-rollouts_gnubg">Rollouts in <span class="application">GNU Backgammon</span></a></span></dt></dl></dd><dt><span class="sect1"><a href="#gnubg-custom">Customizing <span class="application">GNU Backgammon</span></a></span></dt><dd><dl><dt><span class="sect2"><a href="#gnubg-custom_eval">Evaluation settings</a></span></dt><dt><span class="sect2"><a href="#gnubg-custom_appearance">Appearance</a></span></dt></dl></dd><dt><span class="sect1"><a href="#gnubg-technotes">Technical Notes</a></span></dt><dd><dl><dt><span class="sect2"><a href="#gnubg-tech_databases">Obtaining bearoff databases</a></span></dt><dt><span class="sect2"><a href="#gnubg-tech_met">Match Equity Tables</a></span></dt><dt><span class="sect2"><a href="#gnubg-tech_python">Python scripting</a></span></dt><dt><span class="sect2"><a href="#gnubg-tech_equities">Equities explained</a></span></dt><dt><span class="sect2"><a href="#gnubg-tech_postionid">A technical description of the Position ID</a></span></dt><dt><span class="sect2"><a href="#gnubg-tech_matchid">A technical description of the Match ID</a></span></dt><dt><span class="sect2"><a href="#gnubg-tech_css">Description of the CSS style sheet</a></span></dt></dl></dd><dt><span class="sect1"><a href="#gnubg-faq">Frequently Asked Questions</a></span></dt><dd><dl><dt><span class="sect2"><a href="#gnubg-faq_general">General questions</a></span></dt><dt><span class="sect2"><a href="#gnubg-faq_install">How to install</a></span></dt><dt><span class="sect2"><a href="#gnubg-faq_start">Running <span class="application">GNU Backgammon</span></a></span></dt><dt><span class="sect2"><a href="#gnubg-faq_play">Playing backgammon</a></span></dt><dt><span class="sect2"><a href="#gnubg-faq_settings">Settings</a></span></dt><dt><span class="sect2"><a href="#gnubg-faq_analysing">Analysing</a></span></dt><dt><span class="sect2"><a href="#gnubg-faq_abbr">Abbreviations</a></span></dt></dl></dd><dt><span class="appendix"><a href="#legal">A. GNU Free Documentation License</a></span></dt></dl></div><div class="sect1"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="gnubg-intro"></a>Introduction</h2></div><div><div class="abstract"><p class="title"><strong>Abstract</strong></p><p>Introduction to GNU Backgammon</p></div></div></div></div><p>This manual describes how to use <span class="application">GNU
Backgammon</span> to play and analyse backgammon games and
matches. It corresponds to version 1.00.0 (updated in August, 2013).</p><p><span class="application">GNU Backgammon</span> (gnubg)
plays and analyses both money game sessions and tournament matches. It
evaluates and rolls out positions, and much more. Driven by a command-line
interface, it displays an ASCII rendering of a board on text-only terminals,
but also allows the user to play games and manipulate positions with a
graphical GTK+interface. <span class="application">GNU
Backgammon</span> is extensible on platforms which support Python.
</p><div class="screenshot"><div class="mediaobject"><table border="0" summary="manufactured viewport for HTML img" style="cellpadding: 0; cellspacing: 0;" width="100%"><tr><td><img src="images/gtkinterface.png" width="100%" /></td></tr></table></div></div><p><span class="application">GNU Backgammon</span> is a world
class opponent and rates at around 2100 on FIBS, the First Internet
Backgammon Server - at its best, it is in the top 5 of over 6000 rated
players there). <span class="application">GNU Backgammon</span>
can be played on numerous other on-line backgammon servers.</p><p>The following features can be found in the current release of
<span class="application">GNU Backgammon</span>.</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>A command line interface (with full command editing features if
GNU readline is available) that lets you play matches and sessions
against GNU Backgammon with a rough ASCII representation of the board
on text terminals.</p></li><li class="listitem"><p>Support for a GTK+ graphical user interface with both 2D and 3D
views of the board.</p></li><li class="listitem"><p>Tournament match and money session cube handling and cubeful play.
All governed by an underlying cubeless money game based
neural net.</p></li><li class="listitem"><p>Support for both 1-sided and 2-sided bearoff databases: 1-sided
bearoff database for 15 checkers on the first 6 points and optional
2-sided database kept in memory. Larger 1-sided and 2-sided databases
may be stored on disk.</p></li><li class="listitem"><p>Automated rollouts of positions, with lookahead and variance
reduction where appropriate. Rollouts may be extended.</p></li><li class="listitem"><p>Automatic and manual annotation (analysis and commentary) of games
and matches.</p></li><li class="listitem"><p>Record keeping of player statistics in games and matches using relational databases (SQLite, MySQL, and PostgreSQL are supported).</p></li><li class="listitem"><p>Loading and saving analysed games and matches as .sgf files (Smart
Game Format).</p></li><li class="listitem"><p>Importing of positions, games, and matches from a number of
standard file formats, including: native GNU Backgammon file (.sgf),
GamesGrid Save Game (.sgg),
Jellyfish Match (.mat), FIBS Oldmoves (.fibs), Jellyfish Position
(.pos), Snowie Text (.txt), TrueMoneyGames (.tmg), GammonEmpire Game
(.gam), PartyGammon Game (.gam), and BGRoom Game (.bgf).</p></li><li class="listitem"><p>Exporting of positions, games, and matches to a number of
standard file formats, including: native GNU Backgammon file (.sgf),
Hypertext Markup Language (.html), Jellyfish Game (.gam), Jellyfish
Match (.mat), Jellyfish Position (.pos), LaTeX (.tex), Portable
Document Format (.pdf), Plain Text (.txt), Portable Network Graphics
(.png), Postscript (.ps), Snowie Text (.txt), and Scalable Vector
Graphics (.svg).</p></li><li class="listitem"><p>Python Scripting ability.</p></li><li class="listitem"><p>Native language support; 13 languages are complete or in progress:
(cs_CZ, da_DK, en_GB, en_US, es_ES, fr_FR, de_DE, is_IS, it_IT,
ja_JP, ro_RO, ru_RU and tr_TR)</p></li></ul></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="gnubg-intro_gpl"></a>GPL copying/warranty info</h3></div></div></div><p><span class="application">GNU Backgammon</span> is
developed under the GNU General Public License (GPL) and it is part of
the GNU project. For more information about the GNU project please visit their website:
<a class="ulink" href="http://www.gnu.org/" target="_top">http://www.gnu.org/</a> For more information about free software in general please visit The Free
Software Foundation at: <a class="ulink" href="http://www.fsf.org/" target="_top">http://www.fsf.org/</a>.</p></div></div><div class="sect1"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="gnubg-rules"></a>Rules of the game</h2></div></div></div><p>This section describes how to play a game, a match, or a session of
money games against <span class="application">GNU
Backgammon</span> or a human opponent. It is taken directly from
the rules section of <a class="ulink" href="http://www.bkgm.com/" target="_top">Backgammon Galore
</a>, courtesy of Tom Keith.</p><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="gnubg-rules_setup"></a>Setup</h3></div></div></div><p>Backgammon is a game for two players, played on a board consisting
of twenty-four narrow triangles called points. The triangles alternate
in color and are grouped into four quadrants of six triangles each. The
quadrants are referred to as a player's home board and outer board, and
the opponent's home board and outer board. The home and the outer boards
are separated from each other by a ridge down the center of the board
called the bar.</p><div class="figure"><a id="gnubg-fig_init"></a><p class="title"><strong>Figure 1. A board with the checkers in their initial position.</strong></p><div class="figure-contents"><div class="mediaobject"><img src="images/rulfig1.png" alt="A board with the checkers in their initial position." /></div></div></div><br class="figure-break" /><p>An alternate arrangement is the reverse of the one shown here, with
the home board on the left and the outer board on the right.</p><p>The points are numbered for either player starting in that player's
home board. The outermost point is the twenty-four point, which is also
the opponent's one point. Each player has fifteen checkers of his own
color. The initial arrangement of checkers is: two on each player's
twenty-four point, five on each player's thirteen point, three on each
player's eight point, and five on each player's six point.</p><p>Both players have their own pair of dice and a dice cup used for
shaking. A doubling cube, with the numerals 2, 4, 8, 16, 32, and 64 on
its faces, is used to keep track of the current stake of the game.</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="gnubg-rules_object"></a>Object of the Game</h3></div></div></div><p>The object of the game is for a player to move all of his checkers
into his own home board and then bear them off. The first player to bear
off all of his checkers wins the game.</p><div class="figure"><a id="gnubg-fig_direction"></a><p class="title"><strong>Figure 2. Direction of movement of White's checkers. Red's checkers move in
the opposite direction.</strong></p><div class="figure-contents"><div class="mediaobject"><img src="images/rulfig2.png" alt="Direction of movement of White's checkers. Red's checkers move in the opposite direction." /></div></div></div><br class="figure-break" /></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="gnubg-rules_movement"></a>Movement of the Checkers</h3></div></div></div><p>To start the game, each player throws a single die. This determines
both the player to go first and the numbers to be played. If equal
numbers come up, then both players roll again until they roll different
numbers. The player throwing the higher number now moves his checkers
according to the numbers showing on both dice. After the first roll, the
players throw two dice and alternate turns.</p><p>The roll of the dice indicates how many points, or pips, the player
is to move his checkers. The checkers are always moved forward, to a
lower-numbered point. The following rules apply:</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>A checker may be moved only to an open point, one that is not
occupied by two or more opposing checkers. </p></li><li class="listitem"><p>The numbers on the two dice constitute separate moves. For
example, if a player rolls 5 and 3, he may move one checker five
spaces to an open point and another checker three spaces to an open
point, or he may move the one checker a total of eight spaces to an
open point, but only if the intermediate point (either three or five
spaces from the starting point) is also open.</p><div class="figure"><a id="gnubg-fig_opening"></a><p class="title"><strong>Figure 3. White opens the game with 53.</strong></p><div class="figure-contents"><div class="mediaobject"><img src="images/rulfig3.png" alt="White opens the game with 53." /></div></div></div><br class="figure-break" /></li><li class="listitem"><p>A player who rolls doubles plays the numbers shown on the dice
twice. A roll of 6 and 6 means that the player has four sixes to
use, and he may move any combination of checkers he feels
appropriate to complete this requirement. </p></li><li class="listitem"><p>A player must use both numbers of a roll if this is legally
possible (or all four numbers of a double). When only one number can
be played, the player must play that number. Or if either number can
be played but not both, the player must play the larger one. When
neither number can be used, the player loses his turn. In the case
of doubles, when all four numbers cannot be played, the player must
play as many numbers as he can. </p></li></ol></div></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="gnubg-rules_hitting"></a>Hitting and Entering</h3></div></div></div><p>A point occupied by a single checker of either color is called a
blot. If an opposing checker lands on a blot, the blot is hit and placed
on the bar.</p><p>Any time a player has one or more checkers on the bar, his first
obligation is to enter those checker(s) into the opposing home board. A
checker is entered by moving it to an open point corresponding to one of
the numbers on the rolled dice.</p><p>For example, if a player rolls 4 and 6, he may enter a checker onto
either the opponent's four point or six point, so long as the
prospective point is not occupied by two or more of the opponent's
checkers.</p><div class="figure"><a id="gnubg-fig_bar"></a><p class="title"><strong>Figure 4. White rolls 64 with a checker on the bar.</strong></p><div class="figure-contents"><div class="mediaobject"><img src="images/rulfig4.png" alt="White rolls 64 with a checker on the bar." /></div></div></div><br class="figure-break" /><p> If White rolls [64] with a checker on the bar, he must enter the
checker onto Red's four point since Red's six point is not open. If
neither of the points is open, the player loses his turn. If a player is
able to enter some but not all of his checkers, he must enter as many as
he can and then forfeit the remainder of his turn.</p><p>After the last of a player's checkers has been entered, any unused
numbers on the dice must be played, by moving either the checker that
was entered or a different checker.</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="gnubg-rules_bearingoff"></a>Bearing Off</h3></div></div></div><p>Once a player has moved all of his fifteen checkers into his home
board, he may commence bearing off. A player bears off a checker by
rolling a number that corresponds to the point on which the checker
resides, and then removing that checker from the board. Thus, rolling a
6 permits the player to remove a checker from the six point.</p><p>If there is no checker on the point indicated by the roll, the
player must make a legal move using a checker on a higher-numbered
point. If there are no checkers on higher-numbered points, the player is
permitted (and required) to remove a checker from the highest point on
which one of his checkers resides. A player is under no obligation to
bear off if he can make an otherwise legal move.</p><div class="figure"><a id="gnubg-fig_bearoff"></a><p class="title"><strong>Figure 5. White rolls 64 and bears off two checkers.</strong></p><div class="figure-contents"><div class="mediaobject"><img src="images/rulfig5.png" alt="White rolls 64 and bears off two checkers." /></div></div></div><br class="figure-break" /><p>A player must have all of his active checkers in his home board in
order to bear off. If a checker is hit during the bear-off process, the
player must bring that checker back to his home board before continuing
to bear off. The first player to bear off all fifteen checkers wins the
game.</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="gnubg-rules_doubling"></a>Doubling</h3></div></div></div><p>Backgammon is played for an agreed stake per point. Each game starts
at one point. During the course of the game, a player who feels he has a
sufficient advantage may propose doubling the stakes. He may do this
only at the start of his own turn and before he has rolled the dice.</p><p>A player who is offered a double may refuse, in which case he
concedes the game and pays one point. Otherwise, he must accept the
double and play on for the new higher stakes. A player who accepts a
double becomes the owner of the cube and only he may make the next
double.</p><p>Subsequent doubles in the same game are called redoubles. If a
player refuses a redouble, he must pay the number of points that were at
stake prior to the redouble. Otherwise, he becomes the new owner of the
cube and the game continues at twice the previous stakes. There is no
limit to the number of redoubles in a game.</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="gnubg-rules_gammons"></a>Gammons and Backgammons</h3></div></div></div><p>At the end of the game, if the losing player has borne off at least
one checker, he loses only the value showing on the doubling cube (one
point, if there have been no doubles). However, if the loser has
<span class="emphasis"><em>not</em></span> borne off any of his checkers, he is gammoned
and loses <span class="emphasis"><em>twice</em></span> the value of the doubling cube. Or,
worse, if the loser has not borne off any of his checkers and still has
a checker on the bar or in the winner's home board, he is backgammoned
and loses <span class="emphasis"><em>three times</em></span> the value of the double
cube.</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="gnubg-rules_optional"></a>Optional Rules</h3></div></div></div><p>The following optional rules are in widespread use.</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>Automatic doubles. If identical numbers are thrown on the first
roll, the stakes are doubled. The doubling cube is turned to 2 and
remains in the middle. Players usually agree to limit the number of
automatic doubles to one per game.</p></li><li class="listitem"><p>Beavers. When a player is doubled, he may immediately redouble
(beaver) while retaining possession of the cube. The original
doubler has the option of accepting or refusing as with a normal
double. </p></li><li class="listitem"><p>The Jacoby Rule. Gammons and backgammons count only as a single
game if neither player has offered a double during the course of the
game. This rule speeds up play by eliminating situations where a
player avoids doubling so he can play on for a gammon. </p></li></ol></div></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="gnubg-rules_match"></a>Rules for Match Play</h3></div></div></div><p>When backgammon tournaments are held to determine an overall winner,
the usual style of competition is match play. Competitors are paired
off, and each pair plays a series of games to decide which player
progresses to the next round of the tournament. This series of games is
called a match.</p><p>Matches are played to a specified number of points. The first player
to accumulate the required points wins the match. Points are awarded in
the usual manner: one for a single game, two for a gammon, and three for
a backgammon. The doubling cube is used, so the winner receives the value
of the game multiplied by the final value of the doubling cube.</p><p>Matches are normally played using the Crawford rule. The Crawford
rule states that if one player reaches a score one point short of the
match, neither player may offer a double in the immediately following
game. This one game with no doubling is called the Crawford game. If the
Crawford game is won by the trailing player then the doubling cube becomes
available in all subsequent games (and it's most often in the best
interests of the trailing player to double immediately in these games).</p><div class="informaltable"><table border="1"><colgroup><col /><col /><col /><col /></colgroup><tbody><tr><td>Match to 5</td><td>White</td><td>Black</td><td>Doubling</td></tr><tr><td>White wins 2</td><td>2</td><td>0</td><td>Allowed</td></tr><tr><td>Black wins 1 </td><td>2</td><td>1</td><td>Allowed</td></tr><tr><td>White wins 2 </td><td>4</td><td>1</td><td>Allowed</td></tr><tr><td>Black wins 1 </td><td>4</td><td>2</td><td>Crawford Game</td></tr><tr><td>Black wins 2 </td><td>4</td><td>4</td><td>Allowed</td></tr><tr><td>White wins 2 </td><td>6</td><td>4</td><td>Allowed</td></tr></tbody></table></div><p>In this example, White and Black are playing a 5-point match. After
three games White has 4 points, which is just one point short of what he
needs. That triggers the Crawford rule which says there can be no
doubling in next game, Game 4.</p><p>There is no bonus for winning more than the required number of
points in match play. The sole goal is to win the match, and the size of
the victory doesn't matter.</p><p>Automatic doubles, beavers, and the Jacoby rule are not used in
match play.</p></div></div><div class="sect1"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="gnubg-starting"></a>Starting GNU Backgammon</h2></div><div><div class="abstract"><p class="title"><strong>Abstract</strong></p><p>Starting GNU Backgammon. Command line options.</p></div></div></div></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="gnubg-starting_unix"></a>Linux and Unix</h3></div></div></div><p>If <span class="application">GNU Backgammon</span> is
properly installed on your system, you can start it by simply typing
gnubg at the command prompt. If you want to start the GNU Backgammon
command line interface, you can type gnubg --tty or gnubg -t. With this
option, <span class="application">GNU Backgammon</span> starts
without the graphic user interface. There is also other options which
can be added at the start-up.</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="gnubg-starting_ms"></a>Microsoft Windows</h3></div></div></div><p>The builds of <span class="application">GNU
Backgammon</span> which may be downloaded from the <a class="ulink" href="http://www.gnubg.org" target="_top">main <span class="application">GNU
Backgammon</span> page</a> comes with an installation
system. The installation system will create a launch menu item in your
start menu. Usually the menu item can be found by choosing <span class="guimenu">Start</span> → <span class="guimenuitem">Programs</span> → <span class="guimenuitem">GNU Backgammon</span> → <span class="guimenuitem">GNU Backgammon for Windows.</span>.</p><p><span class="application">GNU Backgammon</span> also has a
command line interface. This is supplied as a separate executable file
on Microsoft Windows. You can start this version of <span class="application">GNU Backgammon</span> by choosing <span class="guimenu">Start</span> → <span class="guimenuitem">Programs</span> → <span class="guimenuitem">GNU Backgammon</span> → <span class="guimenuitem">GNU Backgammon Command Line
Interface.</span>
</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="gnubg-starting_mac"></a>Mac OS X</h3></div></div></div><p>Once you have installed both an X11R6 server and <span class="application">GNU Backgammon</span> for Mac OS X, you can run
<span class="application">GNU Backgammon</span> for Mac OS X
by:</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>Start your X11R6 server; </p></li><li class="listitem"><p>Once your X11R6 server is running, in one of its Terminal
windows (by default, Apple's X11 opens one such window at start-up,
and XDarwin opens three), do the following: </p><div class="orderedlist"><ol class="orderedlist" type="a"><li class="listitem"><p>If you have installed <span class="application">GNU
Backgammon</span> in your private Applications folder,
type <span class="command"><strong> cd Applications/gnubg</strong></span> to get into
<span class="application">GNU Backgammon</span> for
Mac OS X's folder, and then type <span class="command"><strong>./gnubg</strong></span> to
run it;</p></li><li class="listitem"><p>If you have installed <span class="application">GNU
Backgammon</span> in the global, top-level Applications
folder, type <span class="command"><strong>cd /Applications/gnubg</strong></span> to get
into <span class="application">GNU Backgammon</span>
for Mac OS X's folder, and type <span class="command"><strong>./gnubg</strong></span> to run
it; </p></li></ol></div></li></ol></div></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="gnubg-starting_options"></a>Command line options</h3></div></div></div><p> The following options control the startup of <span class="application">GNU Backgammon</span>. Most options are
available in all versions of <span class="application">GNU
Backgammon</span>, but notably, the -w and -t options don't work
under MS windows where separate command line and GUI applications exist
instead.</p><div class="example"><a id="gnubg-options"></a><p class="title"><strong>Example 1. GNU Backgammon startup options</strong></p><div class="example-contents"><pre class="programlisting">
Usage:
gnubg [OPTION...] [file.sgf]
Help Options:
-h, --help Show help options
--help-all Show all help options
--help-gtk Show GTK+ Options
Application Options:
-b, --no-bearoff Do not use bearoff database
-c, --commands=FILE Evaluate commands in FILE and exit
-l, --lang=LANG Set language to LANG
-p, --python=FILE Evaluate Python code in FILE and exit
-q, --quiet Disable sound effects
-r, --no-rc Do not read .gnubgrc and .gnubgautorc commands
-S, --splash Show gtk splash screen
-t, --tty Start the command line instead of using the graphical interface
-v, --version Show version information and exit
-w, --window-system-only Ignore tty input when using the graphical interface
-d, --debug Turn on debug
-D, --datadir Specify location of general data
-P, --pkgdatadir Specify location of program specific data
-O, --docdir Specify location of program documentation
-s, --prefsdir Specify location of user's preferences directory
--display=DISPLAY X display to use
</pre></div></div><br class="example-break" /></div></div><div class="sect1"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="gnubg-playing"></a>Playing a game</h2></div></div></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="gnubg-playing_new"></a>Starting a new match or session</h3></div></div></div><p>To start a new game, match or session choose <span class="guimenu">File</span> → <span class="guimenuitem">New</span>, or use the <span class="guibutton">New</span> button in the
toolbar. This will open a dialog box, where you can select the main
options for the new backgammon game you are about to begin. </p><div class="figure"><a id="gnubg-fig_newdialog"></a><p class="title"><strong>Figure 6. The dialog for starting a new match.</strong></p><div class="figure-contents"><div class="mediaobject"><img src="images/newbox.png" alt="The dialog for starting a new match." /></div></div></div><br class="figure-break" /><p>The shortcut buttons are the quickest way to start the game or
match. If you click on the button with the $ sign, you will start a new
money game session immediately. If you click on a numbered button, you
will start a new match of the specified length.</p><p>The dialog allows a fine tuning of the startup options:</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>Use the radio buttons to choose whether you want to start a
match, game or session. If you wish to start a new match, you should
select the match length by typing into the Match length field.
</p></li><li class="listitem"><p>You may play against both the program itself or against a
friend. If you want to start a match or game against a friend,
select the Human vs. Human option.</p></li><li class="listitem"><p>Normally the dice are generated by a random number generator,
but you may use manual dice if you check this option. Then
<span class="application"> GNU Backgammon</span> will prompt for the
dice roll before each roll.</p></li><li class="listitem"><p><span class="application">GNU Backgammon</span> comes with a tutor
mode. If this mode is active, GNU Backgammon analyses each move you
do, and warn you each time you make a mistake. More about tutor mode
later.</p></li><li class="listitem"><p>By clicking on the Modify player settings... button, you will
see the whole player setting dialog. Here you define the playing
strength of <span class="application">GNU Backgammon</span>. This dialog
will be explained later.</p></li></ol></div></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="gnubg-playing_roll"></a>Rolling the dice</h3></div></div></div><p>The simplest way to roll the dice is to click in the right board
area between the board points. You can also roll the dice from the menu <span class="guimenu">Game</span> → <span class="guimenuitem">Roll</span> or with the keyboard shortcut <span class="keycap"><strong>Ctrl</strong></span>+<span class="keycap"><strong>R</strong></span>.</p><div class="figure"><a id="gnubg-fig_roll"></a><p class="title"><strong>Figure 7. Click in the red rectangle to roll the dice.</strong></p><div class="figure-contents"><div class="mediaobject"><img src="images/rolldice.png" alt="Click in the red rectangle to roll the dice." /></div></div></div><br class="figure-break" /><p>When you have moved your checkers to make the desired move, you
complete your turn by clicking on the dice.</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="gnubg-playing_move"></a>Moving the checkers</h3></div></div></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-playing_move_drag"></a>Moving by drag and drop</h4></div></div></div><p>One way to move the checkers is to click on a checker you want to
move and then drag it, while holding the mouse button down, to the
desired designation point. If you have the option Show target help
when dragging checkers enabled, you will see the a green guiding at
any legal target point for the checker you are dragging. You can find
this option by choosing <span class="guimenu">Settings</span> → <span class="guimenuitem">Options...</span> → <span class="guimenuitem">Display</span>
</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-playing_move_click"></a>Moving checkers by clicking</h4></div></div></div><p>Move the mouse cursor over the checker you want to move. If you
now click the <span class="emphasis"><em>left</em></span> mouse button, the checker will
move the pips of the <span class="emphasis"><em>left</em></span> die. If you have
already moved one checker, clicking on a new checker will move it
according to the pips of the remaining die. If you click with the
<span class="emphasis"><em>right</em></span> mouse button on a checker, the checker
will move according to the <span class="emphasis"><em>right</em></span> die.</p><p>Using this method for moving the checkers can be really effective.
Some users prefer showing the higher die to the left. You can make
<span class="application">GNU Backgammon</span> show the highest die to
the left if you choose <span class="guimenu"> Settings </span> → <span class="guimenuitem"> Options... </span> → <span class="guimenuitem"> Dice </span> and check the check box labeled Show higher die on
left.</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-playing_move_undo"></a>Undo a move</h4></div></div></div><p>Before you complete your move by clicking the dice, it's possible
to undo your moves and return to the position before any checkers have
been moved. You can either click the Undo button in the toolbar, or
you can choose <span class="guimenu"> Edit </span> → <span class="guimenuitem"> Undo </span> from the menu or the keyboard shortcut <span class="keycap"><strong>Ctrl</strong></span>+<span class="keycap"><strong>Z</strong></span>.</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-playing_move_shortcut"></a>Some shortcuts</h4></div></div></div><p>There are some shortcuts for moving the checkers. You can
<span class="emphasis"><em>make a new point</em></span> by right clicking on the empty
point that you want to make. As an example, if you roll 31 as the
opening roll, and you want to play 8/5 6/5, you simply place the mouse
cursor on the 5-point and right click. Making points this way also
works if you hit a checker, and with doubles.</p><p>Another shortcut can be used in the bearoff phase of the game. By
clicking in the bearoff tray, <span class="emphasis"><em>two checkers will be born
off</em></span> if such a move is legal.</p><p><span class="application">GNU Backgammon</span> can auto play forced
moves for you. This feature can be enabled by choosing <span class="guimenu"> Settings </span> → <span class="guimenuitem"> Options... </span> → <span class="guimenuitem"> Game </span>, and then check the box Play forced moves
automatically.</p></div></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="gnubg-playing_double"></a>Using the doubling cube</h3></div></div></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-playing_double_offer"></a>Offering a double</h4></div></div></div><p>You offer a double to your opponent by clicking on the cube. This
will offer the cube immediately. You can also click <span class="guimenu">Game</span> → <span class="guimenuitem">Double</span> from the menu or the keyboard shortcut <span class="keycap"><strong>Ctrl</strong></span>+<span class="keycap"><strong>D</strong></span>.</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-playing_double_tp"></a>Accepting or declining a cube</h4></div></div></div><p>You accept a double made by your opponent by clicking on the
offered doubling cube at the board. If you want to decline the double,
you can right click on the cube.</p><p>There are also three buttons in the toolbar for handling cube
offers. These buttons are marked Accept, Decline and Beaver. The
beaver button is only activated in money game sessions where beavers
are allowed.</p><div class="figure"><a id="gnubg-fig_double"></a><p class="title"><strong>Figure 8. The toolbar double buttons.</strong></p><div class="figure-contents"><div class="mediaobject"><img src="images/cubebuttons.png" alt="[[cubebuttons.png]]" /></div></div></div><br class="figure-break" /><p>There are also menu options from the drop down menu for all the
cube actions. Click <span class="guimenu">Game</span> → <span class="guimenuitem">Take</span> from the menu, to accept an offered double(<span class="keycap"><strong>Ctrl</strong></span>+<span class="keycap"><strong>T</strong></span>). Click <span class="guimenu">Game</span> → <span class="guimenuitem">Drop</span>, from the menu, to to decline an offered double(<span class="keycap"><strong>Ctrl</strong></span>+<span class="keycap"><strong>P</strong></span>). Click <span class="guimenu">Game</span> → <span class="guimenuitem">Beaver</span>, from the menu, to beaver an offered double. </p></div></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="gnubg-playing_resign"></a>Resigning</h3></div></div></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-playing_resign_offer"></a>Offering a resignation</h4></div></div></div><p>It's also possible to resign during a game. To resign during play
press the Resign button in the toolbar. This is the button with the
image of a white flag. When this button is pressed, a dialog box will
appear where you can select if you want to resign a single game,
gammon or backgammon. The resignation dialog may also be reached from
the menu system. Click <span class="guimenu">Game</span> → <span class="guimenuitem">Resign</span> to offer your resignation.</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-playing_resign_accept"></a>Accepting or declining a resignation</h4></div></div></div><p>When a resignation is offered a white square will appear on the
board area. The square has a number 1, 2 or 3. A square with a
<span class="emphasis"><em>1</em></span>, means that a single game resignation is
offered, a <span class="emphasis"><em>2</em></span> that a gammon resignation is
offered, and a <span class="emphasis"><em>3</em></span>, means that a backgammon is
offered. If you're using a 3D board, the resignation will be a white
flag instead of a square.</p><p>To accept the resignation click on the numbered square. If you
want to decline the resignation, you right click instead. You can also
use the same toolbar buttons as for accepting or declining a double.
There is also a menu option for accepting and declining resignations.
Click <span class="guimenu">Game</span> → <span class="guimenuitem">Agree to resignation</span> from the menu, to accept an offered resignation. Click <span class="guimenu">Game</span> → <span class="guimenuitem">Decline resignation</span> from the menu, to decline an offered resignation.</p></div></div></div><div class="sect1"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="gnubg-hint"></a>Getting hints and Tutor Mode</h2></div></div></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="gnubg-hint_manual"></a>Getting hints manually</h3></div></div></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-hint_tutor_checker"></a>Getting checker play hints while playing</h4></div></div></div><p>If you want to get a hint of the best move or the best cube action
press the Hint button in the tool bar or the menu option
<span class="guimenu">Analyse</span> → <span class="guimenuitem">Hint</span>.
This will open a hint window.</p><div class="figure"><a id="gnubg-fig_hint"></a><p class="title"><strong>Figure 9. The hint window</strong></p><div class="figure-contents"><div class="mediaobject"><img src="images/hintwindow.png" alt="[[hintwindow.png]]" /></div></div></div><br class="figure-break" /><p>This Hint window shows a list of all possible moves for the position
and dice roll. The different moves are sorted by how <span class="application">GNU
Backgammon</span> ranks each move; there is one move on each
line in the list. The rest of the numbers may look a bit complicated and
cryptic but, once you learn what each number means, it isn't really that
bad.</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p><span class="emphasis"><em>Rank</em></span> is the number that shows
<span class="application">GNU Backgammon</span>'s rank of the move. All
moves evaluated at a given ply are ranked above those evaluated at a
lesser ply. If you use the 0, 1, 2, etc, buttons below the hint list
to re-evaluate one or more moves, the moves will be moved
accordingly. Therefore, for accurate results when re-evaluating a
move that you are interested in, it is usually best to
<span class="emphasis"><em>re-evaluate all moves above it in the list</em></span>.
(And slipping with the mouse and re-evaluating, e.g., a 3-ply move
at 2-ply may make the move <span class="emphasis"><em>disappear</em></span> down to
the bottom of the list!) </p></li><li class="listitem"><p><span class="emphasis"><em>Type</em></span> is a description of the evaluation
that was used to calculate the results. Cubeful means that it is
taking into account the possibility that someone may double.
Occasionally you may see several moves with the equity of -1.000,
(See <span class="emphasis"><em>Equity</em></span> below), despite significantly
different winning percentiles. This is because it thinks that if any
of these moves are played then the opponent will double and you
should pass. The n-ply is the depth to which <span class="application">GNU
Backgammon</span> analysed the move. </p></li><li class="listitem"><p><span class="emphasis"><em>Win</em></span> is the fractions of games that
<span class="application">GNU Backgammon</span> thinks will be won by a
single game, gammon or backgammon. </p></li><li class="listitem"><p><span class="emphasis"><em>Wg</em></span> is the fractions of games that
<span class="application">GNU Backgammon</span> thinks will be won by a
gammon or backgammon. </p></li><li class="listitem"><p><span class="emphasis"><em>Wbg</em></span> is the fractions of games that
<span class="application">GNU Backgammon</span> thinks will be won by a
backgammon. </p></li><li class="listitem"><p><span class="emphasis"><em>Lose</em></span> is the fractions of games that
<span class="application">GNU Backgammon</span> thinks will be lost by a
single game, gammon or backgammon. (Notice that this number is equal
to 1 - Win) </p></li><li class="listitem"><p><span class="emphasis"><em>Lg</em></span> is the fractions of games that
<span class="application">GNU Backgammon</span> thinks will be lost by a
gammon or backgammon. </p></li><li class="listitem"><p><span class="emphasis"><em>Lbg</em></span> is the fractions of games that
<span class="application">GNU Backgammon</span> thinks will be lost by a
backgammon. </p></li><li class="listitem"><p><span class="emphasis"><em>Equity</em></span> is the overall evaluation of the
position by the program, after considering the different win/loss
percentiles, the cube position, and the match score. A 1.000 would
mean that you are expected to win a point, a 0.000 would mean that
it is roughly equal, and a -1.000 that you are expected to lose a
point. When the evaluation is cubeful this number is not computable
by the win/loss brake down of the previous columns. </p></li><li class="listitem"><p><span class="emphasis"><em>Diff.</em></span> is the difference in equity,
perceived in comparison to the top ranked move. </p></li><li class="listitem"><p><span class="emphasis"><em>Move</em></span> is the move being evaluated. In the
case of a red line, it is the move that was played. </p></li></ol></div></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-hint_manual_cube"></a>Getting cube decision hints while playing</h4></div></div></div><p>If you're thinking about a cube decision before rolling you can
press the same Hint button in the toolbar, as you pressed when you
wanted checker play hint. The hint window will again appear, but this
time it will look a bit different and it will show a hint of the correct
cube decision.</p><div class="figure"><a id="gnubg-fig_cubehint"></a><p class="title"><strong>Figure 10. The cube hint window</strong></p><div class="figure-contents"><div class="mediaobject"><img src="images/hintcubewindow.png" alt="[[hintcubewindow.png]]" /></div></div></div><br class="figure-break" /><p>The first lines is the window dialog shows the evaluation depth, and
the cubeless equity with the evaluated probabilities. This equity is
compensated for the match score. The cubeless equity for a money game,
where the the calculation of equity is not compensated for match score,
is also reported.</p><p>Next follow three lines with cubeful equities. In figure above, the
cubeful equity for the player on roll for not doubling at this turn, is
+0.123. The equity for a double and the opponent passing is (of course)
+1.000, since the player then will win one point. (The number is
normalized to cube value of one, so even if it is a redouble to 4 or 8
or higher, the cubeful equity for double/pass is still +1.000 for the
doubler.) The third number in figure above is the cubeful equity for the
player doubling and the opponent accepting the double. The different
option will be listed in order with the best option highest. The number
right to the listed equities is the differences from the cube decision
considered best.</p><p>The last line states the best considered cube action. In the figure
above, <span class="application">GNU Backgammon</span> considers the best cube
action to be No double, take. When percentage number right to the proper
cube action, is a number which indicates the <span class="emphasis"><em>bluff</em></span>
potential. It is the necessary percentage chance you think you can bluff
your opponent into passing the cube to make the double theoretically
correct. This number is only available when the position is considered
No double, take or Too good to double, pass.</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-hint_button"></a>The hint tool buttons</h4></div></div></div><p>As you may see in both figures above, there is a set of buttons
below the move list or cube analysis. Here follows a short description
of what each of the buttons does:</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p><span class="emphasis"><em>Eval</em></span> will evaluate the selected moves, or
the cube decision with the current evaluation setting. </p></li><li class="listitem"><p><span class="emphasis"><em>...</em></span> will open the evaluation setting
dialog. You can then modify the evaluation setting. More about
evaluation settings in the next chapter. </p></li><li class="listitem"><p><span class="emphasis"><em>0 1 2 3 4</em></span> will evaluate the selected moves
or cube decision at cubeful 0-ply or cubeful 1-ply or cubeful 2-ply
and so on. </p></li><li class="listitem"><p><span class="emphasis"><em>Rollout</em></span> will start a rollout ((A
<span class="emphasis"><em>rollout</em></span> is simply a Monte Carlo simulation of
a backgammon position. More about rollouts in a later chapter.)) of
the selected moves or cube decision. </p></li><li class="listitem"><p><span class="emphasis"><em>...</em></span> will open the rollout settings dialog.
This dialog will be further described later in this manual. </p></li><li class="listitem"><p><span class="emphasis"><em>MWC</em></span> (Match Winning Chance). If this button
is pressed the values in the hint window will be shown as the chance
to win the whole match. If this button is unpressed or there is a
money game that's played, the values in the hint window is reported
as Equity. Notice, The equity in a match is actually a recalculation
from match winning chance to equity. This recalculated number is
often referred to as EMG, Equivalent to Money Game. The EMG number
is comparable to the equity in a money game, and are therefore
labeled 'Equity'. </p></li><li class="listitem"><p><span class="emphasis"><em>Show</em></span> will show the board as it would be
after the selected move is made. The button is only available in the
checker play hint window. </p></li><li class="listitem"><p><span class="emphasis"><em>Move</em></span> will make the move selected in the
list. It's also possible to make a move directly from the list by
double clicking on the move. The button is also available only in
the checker play hint window. </p></li><li class="listitem"><p><span class="emphasis"><em>Copy</em></span> will copy the text of all selected
moves to clipboard. </p></li><li class="listitem"><p><span class="emphasis"><em>Temp. Map</em></span> will show Sho Sengoku's
temperature map. This map is further described later in the
document. When this window remembers its size and position it will
really become useful. </p></li></ol></div></div></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="gnubg-hint_tutor"></a>Tutor mode</h3></div></div></div><p>One of the greatest tools for learning, is Tutor Mode. Tutor mode
can be activated by clicking <span class="guimenu">Settings</span> → <span class="guimenuitem">Options...</span> and then click on the Tutor flag. Activate Tutor Mode by
checking the Tutor mode check box.</p><div class="figure"><a id="gnubg-fig_tutor"></a><p class="title"><strong>Figure 11. The tutor window</strong></p><div class="figure-contents"><div class="mediaobject"><img src="images/tutor.png" alt="[[tutor.png]]" /></div></div></div><br class="figure-break" /><p>In Tutor Mode, <span class="application">GNU Backgammon</span> will
analyse your moves and/or cube decisions and compare them with its
choices. You set the threshold for its alerts, for example, if you set
it for bad then it will only warn you when you make a bad mistake. It
will then allow you to re-examine your choice, go right ahead with it,
or provide a 'hint' - essentially, showing you its analysis.</p><p>The tutor can give warnings on both cube decisions and checker play.
If you want the tutor to only warn on cube decisions, you can uncheck
the box for the Checker play. Likewise, if you want it to only warn on
checker play decisions, you can uncheck the box for the Cube decisions.</p><div class="figure"><a id="gnubg-fig_tutorwarn"></a><p class="title"><strong>Figure 12. The tutor warning window</strong></p><div class="figure-contents"><div class="mediaobject"><img src="images/tutorwarning.png" alt="[[tutorwarning.png]]" /></div></div></div><br class="figure-break" /><p>In the above figure, you can see a warning dialog from the tutor
mode. If you press the button labeled Play anyway, the move you made
will be kept and the game will continue. If you press the Rethink
button, the dialog will close and the checkers that you moved will be
returned to their original positions. You can then rethink the position
and try an alternative move. Keep doing this until the Tutor accepts
your move as being good enough. Alternatively you can press the Hint
button to show the hint window with its list of possible moves and their
evaluations. Finally, if you press the End Tutor Mode button, the dialog
will close and turn Tutor Mode off.</p><p>A similar warning window will also appear for poor cube
handling.</p></div></div><div class="sect1"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="gnubg-edit"></a>Setting up a position</h2></div></div></div><p>Think about the Friday night chouette where there was this tough
choice between two move candidates. Which move was the best? Or what about
that match score cube decision from the weekend tournament. Wouldn't it be
nice to be able to set up the position in <span class="application">GNU
Backgammon</span> and ask for its opinion? This is possible in
<span class="application">GNU Backgammon</span>, and it's one of the features
that really can give you the answer to a lot of questions, and in that way
give you a better understanding of the game.</p><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="gnubg-edit_entering"></a>Entering Edit mode</h3></div></div></div><p>To set up a position, you have to be in <span class="emphasis"><em>Edit
mode</em></span>. To enter Edit mode you simply click the Edit button in
the tool bar. There is currently no keyboard shortcut or menu item for
entering edit mode. The Edit button is a toggle button and you will stay
in edit mode until you release the button by clicking it again.</p><p>If your Edit button in the toolbar is disabled it is because there
is no game or match in progress. With the current state of
<span class="application">GNU Backgammon</span> there must be a game or
match in progress to be able to enter edit mode. (This may change in the
future.) If there is no game in progress and you want to set up a
position, you can simply start a new game or match by clicking New in
the toolbar.</p><p>When you are in edit mode you will see the the text (Editing) in the
match information box below the board.</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="gnubg-edit_edit"></a>Editing</h3></div></div></div><p>Setting up a position is basically done by editing the current
position. The editing it self is controlled by clicking different areas
of the board and may not be obvious at first hand.</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="gnubg-edit_clear"></a>Clearing the board</h3></div></div></div><p>In edit mode you can easily clear the board by clicking in one of
the bearoff trays. It's often easier to start setting up a position with
a empty board, so this feature is really handy. When you click on one of
the bearoff tray, all checkers will be moved to the bearoff.</p><div class="figure"><a id="gnubg-fig_clear"></a><p class="title"><strong>Figure 13. Click in the one of the areas marked with a red ellipse to clear
the board.</strong></p><div class="figure-contents"><div class="mediaobject"><img src="images/clearboard.png" alt="[[clearboard.png]]" /></div></div></div><br class="figure-break" /><p>You can also just as easy generate the initial position by clicking
the opposite trays when in edit mode. Clicking in one of these trays
puts all checkers back to the initial position.</p><div class="figure"><a id="gnubg-fig_initpos"></a><p class="title"><strong>Figure 14. Click in the one of the areas marked with a red ellipse to get to
the initial position.</strong></p><div class="figure-contents"><div class="mediaobject"><img src="images/initialboard.png" alt="[[initialboard.png]]" /></div></div></div><br class="figure-break" /><p>Note that the bearoff trays change side when the board is displayed
with clockwise movement.</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="gnubg-edit_quick"></a>Quick edit</h3></div></div></div><p>The default method of editing a position is called <span class="emphasis"><em>Quick
edit</em></span>. It's based on clicking on the point where you want to
place checkers. The number of checkers placed on the point is depending
on where you click, for example if you want to place 3 checkers on a
point, clicking on the location where the third checker would go places
3 checkers. This method should be familiar to Snowie users.</p><p>Clicking with the left button places checkers for player1, clicking
with the right button places checkers for player2. If you want to place
more than 5 checkers, click multiple times on the tip of the point. To
clear a point, click on the border of the board below or above the point
- depending on if the point is in the lower or top half of the board.
The bar works just like normal points - the more you click to the middle
of the bar, the more checkers will be placed there.</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="gnubg-edit_drag"></a>Editing by drag and drop</h3></div></div></div><p>There is also a different way of editing the checker positions. You
can drag and drop checkers around the board while you're holding down
the Ctrl key on your keyboard. Press the Ctrl key and hold it down. Then
left-click the checker you want to drag to another point and drag it
with the mouse, (while holding down the Ctrl key and the left mouse
button), to the destination point. You can drag checkers to open points
or to points where you have checkers of the same color. You can also
'hit' opponent blots with the drag and drop edit method.</p><p>This method of editing comes handy when there is just a small
adjustment to be done in the position.</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="gnubg-edit_turn"></a>Setting the player on turn</h3></div></div></div><p>The player on turn can be set by clicking the small checker icons
below the board. See figure below.</p><div class="figure"><a id="gnubg-fig_turn"></a><p class="title"><strong>Figure 15. Clicking the White checker image will set White on turn, clicking
the Black image will set Black in turn.</strong></p><div class="figure-contents"><div class="mediaobject"><img src="images/setturn.png" alt="[[initialboard.png]]" /></div></div></div><br class="figure-break" /><p>Note that setting the turn sets the turn before the dice has been
rolled. If there is a dice present at the board, setting the turn will
remove the dice rolled. In this way you can set up a position to be a
cube decision evaluation instead of a move decision evaluation.</p><p>The turn can also be set by choosing <span class="guimenu">Game</span> → <span class="guimenuitem">Set turn</span>. Both these methods for setting the player on turn can
also be used without being in edit mode.</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="gnubg-edit_dice"></a>Setting the dice</h3></div></div></div><p>You can set the dice for a player by clicking in the middle part of
the board where you usually click when you roll the dice while playing.
Click in the middle of the right playing area to set the dice for player
0, the bottom player. Click the left dice rolling area to set the dice
for player 1, the top player. Once you click one of these areas the dice
selection widget will appear and you can select a dice roll by clicking
on a dice pair.</p><div class="figure"><a id="gnubg-fig_dice"></a><p class="title"><strong>Figure 16. Click inside the red rectangle to set the dice for Black. Click
inside the green rectangle to set the dice for White.</strong></p><div class="figure-contents"><div class="mediaobject"><img src="images/setdice.png" alt="[[setdice.png]]" /></div></div></div><br class="figure-break" /><p>Setting the dice in edit mode sets both dice and the player on turn.
Setting the dice for player 0, will make player 0 on turn with that
specific dice roll to play.</p><p>This method for setting the dice roll only works in edit mode. If
you're not in edit mode you can set the dice by choosing <span class="guimenu">Game</span> → <span class="guimenuitem">Set dice...</span> from the menu, however this will set the dice for the
player on turn.</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="gnubg-edit_cube"></a>Setting the cube</h3></div></div></div><p>Setting the cube is quite simple while you're in edit mode. Simply
click the cube in the board and the cube selection widget appears.</p><p>Selecting a cube in the first row, where the number is displayed
up-side-down, the top player will be the cube owner. The value of the
cube will be the value of the cube you click in the widget. Note that
the unturned cube is the leftmost cube labeled 64, just as it usually is
on real doubling cube.</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="gnubg-edit_score"></a>Setting the score</h3></div></div></div><p>Very often i backgammon the match score does matter on how the
position is evaluated. <span class="application">GNU Backgammon</span>'s
evaluation algorithms does take the score into account. You can
therefore adjust the the match length and the score to each player while
you're in edit mode.</p><p>In the figure you see that the score fields are editable while
you're in edit mode. Insert the desired match score for each player in
these fields. Player 0, the top player, has the left score field and
player 1, the bottom player, has the right score. You can also set the
match score in the in the match field to the right. There is also a box
to tick whenever the position is from a Crawford game.</p><p>If you want the computer to do a money game evaluation of the
position, you should set the match score to 0 (zero).</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="gnubg-edit_exit"></a>Exiting Edit mode</h3></div></div></div><p>Before you can start analysing the position you have to exit edit
mode. This is done by releasing the Edit button in the toolbar by
clicking it. Note that editing a position destroys your game record with
no warning, so it might be an idea to save your match if you want to
keep it.</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="gnubg-edit_analyse"></a>Analysing the position</h3></div></div></div><p>After you have successfully set up the position you desire, you can
now analyse the position. You can click Hint in the toolbar to get the
best move of cube decision in the same way as described in the chapter
called <a class="xref" href="#gnubg-playing" title="Playing a game">the section called “Playing a game”</a>. Hint, rollouts and evaluations done
from the hint window will not be saved if you try to save the position.
If you want to analyse the position and then be able to save the
position and the analysis results you should rather do a move and then
click back to the move and then choose <span class="guimenu">Analyse</span> → <span class="guimenuitem">Analyse move</span> for the menu. You can then work in the analysis pane on
the right side instead of in the hint window.</p><p>You can enter checkers on a point by clicking on the point. Notice
the amount of checkers you add on a point, depends on where on that
point you click. Left mouse button, black checkers and right mouse
button, red checkers. (assuming you didn't change the colors). You will
get used to this editing. and it makes it much faster to set up a
position.</p><p>See also <a class="ulink" href="http://www.bkgm.com/rgb/rgb.cgi?view+1098" target="_top">Albert Silver's post on GammOnLine</a>
</p></div></div><div class="sect1"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="gnubg-matches"></a>Working with matches</h2></div></div></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="gnubg-matches_ras"></a>Retrieving and storing backgammon files</h3></div></div></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-matches_ras_sgff"></a>The Smart Game Format</h4></div></div></div><p><span class="application">GNU Backgammon</span> uses the Smart Game
Format (SGF) to store games, matches, sessions and positions. SGF is
used in as a standard format for several other turn based games. The
SGF files can store all the rolls and moves and cube decisions as well
as commentary and analysis.</p><p> A game that uses SGF extensively is Go. The format is described
at <a class="ulink" href="http://www.red-bean.com/sgf/" target="_top">this site</a>.
</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-matches_opening"></a>Opening and importing matches</h4></div></div></div><p>Since version 0.16 the GUI recognizes all importable files
automatically (with the exception of the FIBS format). To open or
import a file choose <span class="guimenu">File</span> → <span class="guimenuitem">Open</span>. A file dialog box will appear where you can select the
file and the dialog will inform you of the recognized format, if the
file is importable. You can also use the keyboard shortcut Ctrl-O, or
the tool bar button labeled Open, to open the file dialog box
directly.</p><p>It is still possible to import an unrecognized file by using the
underlying command line interface. Enable the command pane by choosing <span class="guimenu">View</span> → <span class="guimenuitem">Command</span>. In the command pane type in <span class="command"><strong>import oldmoves
<filepath></strong></span> to import, e.g., an oldmoves fibs
formatted file.</p><p>The following table contains the supported formats and the
corresponding commands for manual import of a file.</p><div class="informaltable"><table border="1"><colgroup><col class="c1" /><col class="c2" /></colgroup><tbody><tr><td>FIBS oldmoves format</td><td> <span class="command"><strong>import oldmoves <filepath></strong></span> </td></tr><tr><td>Gamesgrid Save Game</td><td> <span class="command"><strong>import sgg <filepath></strong></span> </td></tr><tr><td>GammonEmpire Game</td><td> <span class="command"><strong>import empire <filepath></strong></span> </td></tr><tr><td>Jellyfish Game</td><td> <span class="command"><strong>import gam <filepath></strong></span> </td></tr><tr><td>Jellyfish Match</td><td> <span class="command"><strong>import mat <filepath></strong></span> </td></tr><tr><td>Jellyfish Position</td><td> <span class="command"><strong>import pos <filepath></strong></span> </td></tr><tr><td>PartyGammon Game</td><td> <span class="command"><strong>import party <filepath></strong></span> </td></tr><tr><td>Snowie Text</td><td> <span class="command"><strong>import snowietxt <filepath></strong></span> </td></tr><tr><td>TrueMoneyGames</td><td> <span class="command"><strong>import tmg <filepath></strong></span> </td></tr></tbody></table></div><p>Jellyfish Match is not formally defined and software exporting matches to this format often produce minor discrepancies.
<span class="application">GNU Backgammon</span> tries to cater to most of them automatically.
</p><p>Online sites do not always create their .mat files with the you as player 1, the one playing towards the bottom of the board.
To have these matches converted to be displayed in the natural way, you can use de CLI command
<span class="command"><strong>set aliases <player name 1>;<player name 2>;[<etc...>]</strong></span>
<span class="application">GNU Backgammon</span> will swap the players as needed so that player names matching these aliases are always imported as player 1.
</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-matches_saving"></a>Saving and exporting positions, games or matches</h4></div></div></div><p>If you have played or imported a match into <span class="application">GNU
Backgammon</span>, and wish to save your efforts, you can
choose <span class="guimenu">File</span> → <span class="guimenuitem">Save</span>. A file dialog box will appear and you can type in a
file name or keep the suggested default file name. (The suggested
default file name contains the date, the players name and the length
of the match). This will save the whole match of the current match or
session. If there is any analysis or commentary available this will
also be saved to the file. You can also use the tool bar button
labeled Save to open the file dialog box directly. There is also a
keyboard shortcut, Ctrl-S, for saving a match or session.</p><p>The export dialog is accessed by choosing <span class="guimenu">File</span> → <span class="guimenuitem">Export</span> This dialog is similar to the save dialog. Again you may
choose a different filename and whether to export an entire match, a
game or a position. Then you must choose an export format as well.
Notice some file formats only supports export of matches and some only
supports position. Only when a legal combination is chosen will ending
the dialog be possible. The following table contains the supported
file formats and the corresponding commands for export. Again notice
that with some formats only some of M(atch), G(ame), P(osition) is
allowed. For example to export a Jellyfish position you would issue
the command <span class="command"><strong>export position pos
<filepath></strong></span></p><div class="informaltable"><table border="1"><colgroup><col class="c1" /><col class="c2" /></colgroup><tbody><tr><td>Encapsulated Postscript</td><td> <span class="command"><strong>export <P> eps <filepath></strong></span> </td></tr><tr><td>HTML</td><td> <span class="command"><strong>export <MGP> html <filepath></strong></span> </td></tr><tr><td>Jellyfish Game</td><td> <span class="command"><strong>export <G> gam <filepath></strong></span> </td></tr><tr><td>Jellyfish Match</td><td> <span class="command"><strong>export <M> mat <filepath></strong></span> </td></tr><tr><td>Jellyfish Position</td><td> <span class="command"><strong>export <P> pos <filepath></strong></span> </td></tr><tr><td>LaTeX</td><td> <span class="command"><strong>export <MG> latex <filepath></strong></span> </td></tr><tr><td>PDF</td><td> <span class="command"><strong>export <MG> pdf <filepath></strong></span> </td></tr><tr><td>Plain Text</td><td> <span class="command"><strong>export <MGP> text <filepath></strong></span> </td></tr><tr><td>Portable Network Graphics</td><td> <span class="command"><strong>export <P> pdf <filepath></strong></span> </td></tr><tr><td>PostScript</td><td> <span class="command"><strong>export <MG> postscript <filepath></strong></span> </td></tr><tr><td>Snowie Text</td><td> <span class="command"><strong>export <P> snowietxt <filepath></strong></span>
</td></tr></tbody></table></div><div class="sect4"><div class="titlepage"><div><div><h5 class="title"><a id="gnubg-matches_saving_html"></a>HTML export</h5></div></div></div><p><span class="application">GNU Backgammon</span> can export the current
position, game, match or session in HTML if you wish to publish it
on the web. </p><p><span class="application">GNU Backgammon</span> exports in validating
XHTML 1.0 with the use of CSS style sheets. You may add your own
style sheet to the exported HTML files if you wish to override the
default layout, e.g., change colors or fonts.</p><p>The board is made up from hundreds of pictures. Currently, you
can choose between three different sets of pictures:</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>the BBS images used by Kit Woolsey's GammOnLine e-magazine,
Danish Backgammon Federation's web-based discussion group and
others </p></li><li class="listitem"><p>the fibs2html images used by the Joseph Heled's program
<a class="ulink" href="http://fibs2html.sourceforge.net/" target="_top">fibs2html</a>
</p></li><li class="listitem"><p>images generated by <span class="application">GNU
Backgammon</span> itself. </p></li></ol></div><p>The images generated by <span class="application">GNU
Backgammon</span> will use your current board design in
<span class="application">GNU Backgammon</span>, and honors your
settings on clockwise or anti-clockwise movement and board numbering
(on, off, dynamic).</p><p>If you export a match or session to HTML, <span class="application">GNU
Backgammon</span> will write the individual games to
separate files. For example, if you export to file foo.html the
first game is exported to foo.html, the second game to foo_002.html,
the third game to foo_003.html and so forth.</p><p>The output from the HTML export can be customized. For example,
it's possible to leave out the analysis or parts of the analysis.
Also, you may enter a specific URL to the pictures used to compose
the board which is useful for posting positions on web-based
discussion groups such as Kit Woolsey's GammOnLine, the Danish
Backgammon Federation's Debat Forum.</p><p>If you want to have html images locally on your computer, you
can have <span class="application">GNU Backgammon</span> generate these.
The html images will be generated based on the current appearance
settings. You can also control the size of the images in the export
settings dialog (To get the export settings dialog you can select in
the menu <span class="guimenu">Settings</span> → <span class="guimenuitem">Export...</span>. Select the size of your html images at the bottom
right in this dialog</p><p>To start the generation of the html images, select in the menu <span class="guimenu">File</span> → <span class="guimenuitem">Export</span> → <span class="guimenuitem">HTML images...</span>. In the file dialog box, you can select a
<span class="emphasis"><em>directory</em></span> where the images will be generated.
The images are stored in PNG format.</p><p>To generate images for the command line, use the command:</p><p>export htmlimages directory</p><p>where directory is the directory where you want your images to
be created.</p></div><div class="sect4"><div class="titlepage"><div><div><h5 class="title"><a id="gnubg-matches_saving_latex"></a>LaTeX export</h5></div></div></div><p><span class="application">GNU Backgammon</span> can export games,
match and positions to the document typesetting system LaTeX. For
exporting a match or session to LaTeX</p><p>The LaTeX export will export all board diagrams and analysis if
available. The produced documents can therefore be quite large. Note
that the LaTeX file produced needs the eepic package. You can get
this package at your nearest CTAN mirror((The produced LaTeX file
also needs epic, textcomp and ucs, but these are more common in
LaTeX distributions so you probably already have these.)).</p><p>You can not export a position to LaTeX. (At least not yet!)
However, you can export a position to EPS and include this EPS file
in your LaTeX document.</p></div></div></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="gnubg-matches_entering"></a>Entering live tournament matches</h3></div></div></div><p>It's possible to enter match transcriptions into <span class="application">GNU
Backgammon</span>. It's not very difficult. Presuming you're
using the GUI, do this:</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>Start a match of any length, pressing the New button, and select
Human-Human and manual dice. </p></li><li class="listitem"><p>To select the opening roll, click on the right dice pair in the
dice selection window that appears. The left die in the dice pair is
the die that's rolled by player 0, or the player at the top. The
right die is the die that will be rolled by player 1 or the bottom
player. So if you select for example the 53 dice combination it
means that player 0 rolls a 5 and player 1 rolls a 3, and player 0
is therefore beginning this game. However, if you select the 35 dice
combination it means that player 0 rolls a 3 and player 1 rolls a 5.
Player 1 will therefore begin when you select 53 instead of 35.
</p></li><li class="listitem"><p>To change the names, use the Edit button at the top. If you want
to enter information such as the name of the Annotator, date,
locale, etc. go to the Game menu and choose Match Information.
</p></li><li class="listitem"><p>To enter written comments, you first have to play the move, and
then go back to the move in the move list to be able to use the
Commentary pane (feel free to close the Messages pane from the
Windows menu). Don't forget to save the match every once in a while.
</p></li><li class="listitem"><p>One comment: when entering the Cube commentary of a cube play
(meaning it was turned), select the Take/Pass decision to enter the
commentary. The reason is that if you export it after, and didn't do
this, the commentary appears before the cube decision and not after
as it should. </p></li></ol></div><p>Tip: while entering the match, if you wish to see <span class="application">GNU
Backgammon</span>'s opinion while you are entering the moves,
play the move on the board and press the Hint button in the tool bar. In
the latest builds, if you have done this, the results will then be
placed with the move so that it means it is already analysed when you
run the full match analysis. Mind you, it will preserve the information
even if you ran a deeper 3-ply or 4-ply from the Hint window. After
playing the move and confirming the dice, go back in the move list and
click on the move, and you'll see the analysis appear in the Analysis
pane as it should.</p><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-matches_entering_illegal"></a>Entering illegal moves</h4></div></div></div><p>It's possible to enter illegal moves with a little trick. This is a
step by step guide for the example: If a player rolls 41 and the player
makes an illegal move as the dice showed 31.</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>Manually enter the roll which was rolled. 41. </p></li><li class="listitem"><p>Do a legal move with 41 (this is just to get the analysis of the
roll, and the best legal move.) </p></li><li class="listitem"><p>Click the dice to pick them up and complete the move. </p></li><li class="listitem"><p>Now, before you roll the opponents dice, click the Edit button.
</p></li><li class="listitem"><p>While holding down the CTRL-button on your keyboard, you can now
drag the checkers to the resulting illegal position which was played
over the board. </p></li><li class="listitem"><p>Release the Edit button to exit edit mode. </p></li><li class="listitem"><p>Make sure the right player is on turn, by clicking on the
checker image for the player on roll, under the game board. </p></li><li class="listitem"><p>Continue to enter the rest of the game. </p></li></ol></div></div></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="gnubg-matches_analysing"></a>Analysing matches</h3></div></div></div><p><span class="application">GNU Backgammon</span> can analyse your matches
for skill and luck. If you have an open match (as a result of playing,
loading or importing), the analysis is started by choosing <span class="guimenu">Analyse</span> → <span class="guimenuitem">Analyse match</span>. You should now see a progress bar at the bottom right
corner of the main interface window while the computer is busy
analysing. During this time you won't be able to interact with the
program other than to quit the analysis. The analysis is complete when
the progress bar disappears and you hear a small sound. Now, you would
probably like to view the result of the analysis. This can be done in
terms of overall statistics by choosing <span class="guimenu">Analyse</span> → <span class="guimenuitem">Match statistics</span>, or in detail by browsing through the match. More on these
subjects in the upcoming sections.</p><p>You can also analyse just the current game, by choosing <span class="guimenu">Analyse</span> → <span class="guimenuitem">Analyse game</span>. If you're only interested in the analysis of the current
move, you can select <span class="guimenu">Analyse</span> → <span class="guimenuitem">Analyse move</span>.</p><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-matches_analysing_settings"></a>Analysis settings</h4></div></div></div><p>You can configure how <span class="application">GNU Backgammon</span>
analysis the match or game for you. This can be configured in the dialog
box that appears when choose <span class="guimenu">Settings</span> → <span class="guimenuitem">Analysis</span>.</p><div class="figure"><a id="gnubg-fig_analyse"></a><p class="title"><strong>Figure 17. Analyse settings dialog</strong></p><div class="figure-contents"><div class="mediaobject"><img src="images/analysesettings.png" alt="[[analysesettings.png]]" /></div></div></div><br class="figure-break" /><p>In the top left frame in this dialog box, you can select what to
analyse. <span class="application">GNU Backgammon</span> is able to analyse
three different properties in a match.</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>Checker play </p></li><li class="listitem"><p>Cube decisions </p></li><li class="listitem"><p>Luck of each roll </p></li></ol></div><p>In addition you can have the analysis to analyse just one of the
players, or both. There is also possible to set a limit of how many
moves to be analysed at each position. When you're reviewing your match,
the number of analysed moves will be limited to number in this field.
However, if you want to analyse further moves in a particular position,
it's not a problem to do that later. The move that was actually done in
the match will be analysed even if it is ranked below the number of
moves limit.</p><p><span class="application">GNU Backgammon</span> will also mark each move
or cube decision with Doubtful, Bad and Very bad. You can adjust the
limits in equity difference for which label to assign. This is done in
the frame box to the left. Notice, currently the Good and Very good
classes are not used.</p><p>You can also adjust the classes for what <span class="application">GNU
Backgammon</span> considers lucky and unlucky rolls. The luck of
a roll is defined as the difference of equity after the best move after
rolled dice and the equity after best move averaged over all possible
rolls.</p><p>The right part of the dialog box is an evaluation setting for how
each move or cube decision should be evaluated in the analysis. For an
explanation of this settings, see the chapter called "[[Evaluation
settings]]".</p></div></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="gnubg-matches_review"></a>Reviewing matches</h3></div></div></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-matches_review_record"></a>Game record</h4></div></div></div><p>When a match is analysed in <span class="application">GNU
Backgammon</span> you should open the <span class="emphasis"><em>game
record</em></span> window. Open this by checking <span class="guimenu">Window</span> → <span class="guimenuitem">Game record</span> on from the main menu. The game record window can also
be docked into the right side panel. If you want it docked into the
right side panel you should check on <span class="guimenu">Window</span> → <span class="guimenuitem">Dock panels</span>. The game record window shows a list of all the moves in
the game. You can also navigate between the games and moves.</p><div class="figure"><a id="gnubg-fig_record"></a><p class="title"><strong>Figure 18. The Game record pane</strong></p><div class="figure-contents"><div class="mediaobject"><img src="images/gamerecord.png" alt="[[gamerecord.png]]" /></div></div></div><br class="figure-break" /><p>The figure shows a typical game record list. The moves are shown
in two columns. The left column shows the moves for player 0,the to
player, and the right column shows the moves of player 1, the bottom
player. You can navigate through the game with the arrow buttons at
the top of the game record. The red buttons with the double arrows
take you to the previous game or the next match. (Arrow pointing to
the left takes you to the previous game, and the red arrow pointing to
the right takes you to the next game.) The green buttons take you one
move ahead in the game or one move back. The green arrow button
pointing to the right take you to the previous move. The green arrow
button pointing to the right take you to the next move or to the next
dice roll. If your in the move list where the dice is not rolled, a
click on this green Next button will show you the same position with
the dice rolled. The last two buttons take you to the next marked
move, or to the previous marked move. The green arrow button with a
question mark pointing to the left will take you to the previous
marked move. The green arrow button with a question mark pointing to
the right will take you to the next marked move. You can also go to
other games in the match or session by selecting the game in the game
drop down menu. You can also go to a move directly by clicking that
move in the game record list.</p><p>There is also some keyboard shortcuts for navigating through the
match. Page Down till take you to the next move and Page up will take
you to the previous move.</p><p>After a analysis some of the move in the game list will be marked.
You will see some moves marked with <span class="emphasis"><em>?</em></span> and some
with <span class="emphasis"><em>?!</em></span> and some with <span class="emphasis"><em>??</em></span>.
These marks means the same as the marks in normal chess notation.</p><div class="informaltable"><table border="1"><colgroup><col class="c1" /><col class="c2" /></colgroup><tbody><tr><td>??</td><td>a very bad move</td></tr><tr><td>?</td><td>a bad move</td></tr><tr><td>?!</td><td>a doubtful move</td></tr></tbody></table></div><p>Note that it is the same marks for cube decisions as for checker
moves. Nevertheless, checker moves marks are before the cube decisions
marks. If no mark exists for checker move, the cube mark is separated
by two spaces.</p><p>In newer builds of <span class="application">GNU Backgammon</span> the
various moves also get a color code. The cube decisions are shown by
the background color. The checkers move decisions are shown by the
font color.</p><div class="informaltable"><table border="1"><colgroup><col /><col /><col /></colgroup><tbody><tr><td> </td><td>Cube(background)</td><td>Move(font)</td></tr><tr><td>Very Bad</td><td>Yellow</td><td>Red</td></tr><tr><td>Bad</td><td>Pink</td><td>Blue</td></tr><tr><td>Doubtful</td><td>Grey</td><td>Green</td></tr></tbody></table></div><p>The luck is also marked in the font</p><div class="informaltable"><table border="1"><colgroup><col /><col /></colgroup><tbody><tr><td>Luck</td><td>Font</td></tr><tr><td>Very Lucky</td><td>Bold</td></tr><tr><td>Very Unlucky</td><td>Italics</td></tr></tbody></table></div></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-matches_review_analysis"></a>Analysis panel</h4></div></div></div><p>You can also study your moves and cube decisions in more detail in
the analysis window, or analysis panel if you have checked Dock panels
in the Window menu. You can open this window by checking on <span class="guimenu">Window</span> → <span class="guimenuitem">Analysis</span>. If you have docked panels the analysis panel will
appear under the game record. The analysis window is basically the
same as the Hint window described in the "[[Playing a game or match]]"
chapter.</p><div class="figure"><a id="gnubg-fig_analysepane"></a><p class="title"><strong>Figure 19. The Analyse pane</strong></p><div class="figure-contents"><div class="mediaobject"><img src="images/analysepane.png" alt="[[analasyepane.png]]" /></div></div></div><br class="figure-break" /><p>In the figure you can see the analysis panel. At the top of the
analysis panel you will see three pull-down menus. The leftmost
pull-down menu is a comment on the cube decision. In the figure it is
a position where the player didn't double and the <span class="application">GNU
Backgammon</span>'s analysis of this is empty. There was
nothing wrong with not doubling in this position. The user can also
override <span class="application">GNU Backgammon</span>'s evaluation and
mark the cube decision as 'Doubtful', 'Bad' or 'Very bad'. Note that
the cube decision pull-down menu will only be visible when the player
has the cube available.</p><p>The next pull-down menu shows a simple analysis of the roll. The
roll in this position was 32. <span class="application">GNU
Backgammon</span>'s evaluation of this dice roll is also empty.
It shows that this particular roll was -.162 equity worse than the
average roll. This means that the roll is a bit unlucky, but does not
qualify for being marked as an unlucky roll. The rolls are marked in
these categories: 'Very lucky', 'Lucky', 'Unlucky' and 'Very unlucky'.</p><p>The rightmost pull-down menu, shows the move which was done. In
this situation the move that was done was 3/off 2/off. This move did
not qualify for any mark. Moves that <span class="application">GNU
Backgammon</span> don't like will be marked as 'Doubtful',
'Bad' or 'Very bad'. The user can also override <span class="application">GNU
Backgammon</span>'s evaluation and mark the move manually
with the pull-down menu.</p><p>The rest of the analysis window is a notebook of two pages. The
first page is the list of possible moves. The list is sorted in the
ranked order with the best considered move at the top. The moves are
sorted by equity or EMG. In the list in the figure there is only two
possible moves. The move that was actually done in the match, is
marked with red color. The only difference of this list of moves and
the list of moves in the hint window, is that this list does not show
the probabilities for each outcome of the game. If you want to see the
probabilities of the different outcomes, you can click on the button
labeled Details. This will then show you a list with these numbers.</p><p>The other page of the notebook is the cube decision analysis. This
analysis show exactly the same as in the Hint window described in the
chapter called "[[Playing a game or match]]". Note that the cube
decision page will only be available if there is a cube decision. It
will not be visible if the cube is not available to the player.</p><p>There is also a set of tool buttons in the analysis panel. These
buttons does exactly the same as the tool buttons in the Hint window,
which is described in the the chapter called "[[Playing a game or
match]]".</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-matches_review_stat"></a>Statistics</h4></div></div></div><p>You can get a summary of the analysis from the game, match, or
session analysis. The game analysis is a summary for the current game
whereas the match or session statistics is a summary of all the games
in the match or session. The match analysis is available in the GUI
from <span class="guimenu">Analyse</span> → <span class="guimenuitem">Match Statistics</span> or at the bottom of exported files.</p><div class="sect4"><div class="titlepage"><div><div><h5 class="title"><a id="gnubg-matches_review_stat_check"></a>Checker play statistics</h5></div></div></div><p>This section provides a summary of the checker play statistics.
The following information is available</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>Total moves: The total number of moves in the match. </p></li><li class="listitem"><p>Unforced moves: The number of unforced moves, i.e., all
checker play decisions which had more than one legal move.
</p></li><li class="listitem"><p>Moves marked <span class="emphasis"><em>xxx</em></span>: The number of moves
marked <span class="emphasis"><em>very good</em></span>, <span class="emphasis"><em>very
bad</em></span> etc. The analysis will mark moves <span class="emphasis"><em>very
bad</em></span>, <span class="emphasis"><em>bad</em></span> etc. based on the
threshold you've defined in the analysis settings.
<span class="application">GNU Backgammon</span> can currently not
automatically mark moves, e.g., <span class="emphasis"><em>good</em></span>, but
you can mark moves <span class="emphasis"><em>good</em></span> yourself. </p></li><li class="listitem"><p>Error rate (total): The first number is the total amount of
normalized equity that the player gave up during this game or
match. The number in parenthesis is the un-normalized
counterpart; for money play the all errors are multiplied with
the value of the cube, and for match play the total match
winning chance given up by the player is reported. </p></li><li class="listitem"><p>Error rate (per move): The error rate per move is the total
error rate divided by the number of <span class="emphasis"><em>unforced
moves</em></span>. Note that is different from Snowie 4 that
defines the error rate per move as the total error rate divided
by the total number of moves for both players, i.e., the sum of
<span class="emphasis"><em>total moves</em></span> for both players. In general,
your error rate per move will be lower in Snowie than in
<span class="application">GNU Backgammon</span>. </p></li><li class="listitem"><p>Checker play rating: <span class="application">GNU
Backgammon</span> will assign a rating for your checker
play ranging from <span class="emphasis"><em>Awful!</em></span> to
<span class="emphasis"><em>Supernatural</em></span>. See the description for the
overall rating below. </p></li></ol></div></div><div class="sect4"><div class="titlepage"><div><div><h5 class="title"><a id="gnubg-matches_review_stat_luck"></a>Luck analysis</h5></div></div></div><p>This section provides information about how Ms. Fortuna
distributed her luck. The following information is available:</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>Rolls marked <span class="emphasis"><em>xxx</em></span>: The number of moves
marked <span class="emphasis"><em>very lucky</em></span>,
<span class="emphasis"><em>lucky</em></span> etc. Moves marked <span class="emphasis"><em>very
lucky</em></span> are huge jokers that improve your equity with
more the +0.6 relative to the average equity. <span class="application">GNU
Backgammon</span> normally uses cubeful 0-ply
evaluations to calculate the luck, but you can change that under
the analysis settings. See below for a complete overview of what
is considered <span class="emphasis"><em>very lucky</em></span>,
<span class="emphasis"><em>lucky</em></span>, etc. </p></li><li class="listitem"><p>Luck rate (total): The total luck for this game or match
reported both normalized and unnormalized. </p></li><li class="listitem"><p>Luck rate (per move): The luck rate per move reported both
normalized and unnormalized. </p></li><li class="listitem"><p>Luck rating: Based on the luck rate per move
<span class="application">GNU Backgammon</span> will assign you a
humorous luck rating. See below for the possible ratings.
</p></li></ol></div><p>Thresholds for marking of rolls:</p><div class="informaltable"><table border="1"><colgroup><col class="c1" /><col class="c2" /></colgroup><tbody><tr><td>Deviation of equity from average</td><td>Roll is marked</td></tr><tr><td>> 0.6</td><td>very lucky</td></tr><tr><td>0.3 - 0.6</td><td>lucky</td></tr><tr><td>-0.3 - 0.3</td><td>unmarked</td></tr><tr><td>-0.6 - -0.3</td><td>unlucky</td></tr><tr><td>< -0.6</td><td>very unlucky</td></tr></tbody></table></div><p>Luck ratings:</p><div class="informaltable"><table border="1"><colgroup><col class="c1" /><col class="c2" /></colgroup><tbody><tr><td>Normalized luck rate per move</td><td>Luck rating</td></tr><tr><td>> 0.10</td><td>Cheater :-)</td></tr><tr><td>0.06 - 0.10</td><td>Go to Las Vegas immediately</td></tr><tr><td>0.02 - 0.06</td><td>Good dice, man!</td></tr><tr><td>-0.02 - 0.02</td><td>none</td></tr><tr><td>-0.06 - -0.02</td><td>Better luck next time</td></tr><tr><td>-0.06 - -0.10</td><td>Go to bed</td></tr><tr><td>< -0.10</td><td>Haaa-haaa</td></tr></tbody></table></div></div><div class="sect4"><div class="titlepage"><div><div><h5 class="title"><a id="gnubg-matches_review_stat_cube"></a>Cube statistics</h5></div></div></div><p>This section provides a summary of the cube decision statistics:
the number of cube decisions, missed doubles, etc.</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>Total cube decisions: The total number of cube decisions,
i.e., the sum of no-doubles, doubles, takes, and passes. </p></li><li class="listitem"><p>Close or actual cube decisions: Similar to Total cube
decisions, except that no-doubles are only included if they're
considered <span class="emphasis"><em>close</em></span>. <span class="application">GNU
Backgammon</span> considers a cube decision close if
the relevant equities are within 0.16 from each other or if the
position is too good. </p></li><li class="listitem"><p>Doubles, Takes, Passes: The total number of doubles, takes,
and passes in the game or match. </p></li><li class="listitem"><p>Missed doubles around DP, Missed doubles around TG: The
number of missed doubles around the double point and too good
point respectively. If the equity is below 0.95 the position is
considered to be around the double point else it considered to
be around the too good point. If you miss doubles around the
double point, it usually means that you double too late, whereas
missed doubles around the too good point means that you're too
greedy and play on for gammon when the position is
<span class="emphasis"><em>not</em></span> too good. </p></li><li class="listitem"><p>Wrong doubles around DP, Wrong doubles around TG: The number
of wrong doubles around the double point and too good point,
respectively. If you have wrong doubles around the double point
that generally means that you double too early where you really
should hold the cube, whereas wrong doubles around the too good
point means that you double positions where you really should
play on for a gammon or backgammon. </p></li><li class="listitem"><p>Wrong takes, Wrong passes: The total number of wrong takes
and passes, respectively. </p></li><li class="listitem"><p>Error rate (total): The accumulated cube errors for this
game or match reported both normalized and unnormalized. </p></li><li class="listitem"><p>Error rate (per cube decision): The error rate per cube
decision is the total error rate divided by the number of
<span class="emphasis"><em>close or actual cube decisions</em></span>. Note that
is different from Snowie 4 that defines the error rate per cube
decision as the total error rate divided by the total number of
moves for both players. In general, your error rate per cube
decision will be lower in Snowie than in <span class="application">GNU
Backgammon</span>. Note that the reported number is
multiplied by 1000 in the default settings. </p></li><li class="listitem"><p>Cube decision rating: <span class="application">GNU
Backgammon</span> will assign a rating for your cube
decisions ranging from <span class="emphasis"><em>Awful!</em></span> to
<span class="emphasis"><em>Supernatural</em></span>. See the description for the
overall rating below. </p></li></ol></div></div><div class="sect4"><div class="titlepage"><div><div><h5 class="title"><a id="gnubg-matches_review_stat_overall"></a>Overall rating</h5></div></div></div><p>The last section is the overall summary.</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>Error rate (total): The accumulated checker play and cube
decision errors reported by normalized and unnormalized. </p></li><li class="listitem"><p>Error rate (per decision): The error rate per decision is
the total error rate divided by the number of non-trivial
decisions (i.e., the sum of <span class="emphasis"><em>unforced moves</em></span>
and <span class="emphasis"><em>close or actual cube decisions</em></span>). Again,
please note that is different from Snowie 4 that defines the
error rate per decision as the total error rate divided by the
total number of moves for both players. In general, your error
rate per move will be lower in Snowie than in <span class="application">GNU
Backgammon</span>. An investigation of approximately
300 matches showed the on average the <span class="application">GNU
Backgammon</span> error rate with be 1.4 times higher
than your Snowie 4 error rate. </p></li><li class="listitem"><p>Equivalent Snowie error rate: For easy comparison
<span class="application">GNU Backgammon</span> will also print the
total error rate calculated by the same formula as Snowie 4.
</p></li><li class="listitem"><p>Overall rating: Based on your normalized error rate per move
GNU Backgammon will assign you a rating ranging from
<span class="emphasis"><em>Awful!</em></span> to
<span class="emphasis"><em>Supernatural</em></span>. See the table below for the
thresholds. </p></li><li class="listitem"><p>Actual result: The actual result of the game or match. For
money game this is simply the number of points won or lost
during the game or match. For match play the number is
calculated as 50% added to the result of the game or match in
MWC. For example, losing a match or winning a match corresponds
to an actual result of 0% and 100%, respectively. Winning 1
point in the first game of 7 point match is worth 6% using Kit
Woolsey's match equity table, hence the actual result is 56%.
</p></li><li class="listitem"><p>Luck adjusted result: The luck adjusted result is calculated
as the <span class="emphasis"><em>actual result</em></span> plus the total
unnormalized luck rate. This is also called <span class="emphasis"><em>variance
reduction of skill</em></span> as described in Douglas Zare's
excellent article <a class="ulink" href="http://www.bkgm.com/articles/Zare/HedgingTowardSkill.html" target="_top">
Hedging Toward Skill</a>. This should give an unbiased
measure of the strengths of the players. </p></li><li class="listitem"><p>MWC against current opponent: For match play
<span class="application">GNU Backgammon</span> will calculate your
MWC against the current opponent. The number is calculated as
50% - your total unnormalized error rate + your opponent's total
unnormalized error rate. If your opponent is really lucky but
plays rather bad, this number can become larger than 100%, since
he due to the extra luck has the possibly to give up even more
MWC. However, <span class="application">GNU Backgammon</span> will
report this number as 100%, and 0% for the opposite situation.
Note that this number is biased towards the analysing bot, e.g.,
a 0-ply analysis a game between GNU Backgammon 2-ply and 0-ply
will suggest that 0-ply is a favorite, which it is clearly not.
For an unbiased measure use the <span class="emphasis"><em>luck adjusted
result</em></span> above. </p></li></ol></div><p>Threshold for ratings:</p><div class="informaltable"><table border="1"><colgroup><col class="c1" /><col class="c2" /></colgroup><tbody><tr><td>Normalized total error rate per move</td><td>Rating</td></tr><tr><td>0.000 - 0.002</td><td>Supernatural</td></tr><tr><td>0.002 - 0.005</td><td>World Class</td></tr><tr><td>0.005 - 0.008</td><td>Expert</td></tr><tr><td>0.008 - 0.012</td><td>Advanced</td></tr><tr><td>0.012 - 0.018</td><td>Intermediate</td></tr><tr><td>0.018 - 0.026</td><td>Casual Player</td></tr><tr><td>0.026 - 0.035</td><td>Beginner</td></tr><tr><td>> 0.035</td><td>Awful!</td></tr></tbody></table></div><p>Please note: The Normalized total error rate per move is
multiplied by 1000 in the default settings.</p></div></div></div></div><div class="sect1"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="gnubg-rollouts"></a>Rollouts</h2></div></div></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="gnubg-rollouts_intro"></a>Introduction to rollouts</h3></div></div></div><p>The million dollar question is simple enough: out of all the games
that could result from playing this position, how many do we win (and
how many of our wins and losses are gammons, and how many are
backgammons)? The model is exactly the same as if we had an urn with a
googol balls in it (it's a big urn), and many of the balls have win
written on them, and some say gammon loss, and if we look hard enough
there are a few that read backgammon win, and so on. (Balls and urns
are to probability theorists what teapots and checkerboards are to
computer graphics researchers, or <span class="emphasis"><em>squeamish
ossifrage</em></span> is to cryptographers; they seem to come with the
territory.) Instead of having the patience to count the googol balls,
we just give the urn a really good shake and then pull 100 balls out
without looking, and say for instance "Well, I got 53 wins, 31 losses, 9
gammon wins, 6 gammon losses, and a backgammon win. It looks like my
equity's roughly +0.26." and go home. If we were a bit more thorough, we
could go a bit further and figure out that by cheating and measuring the
sample proportions instead of the population proportions, we introduced
a standard error of 0.06 into our result. (Of course, the trick is to
select a sample size that's big enough that you reduce the standard
error to a tolerable level, but small enough that the answer arrives
before you get bored.)</p><p>It will come as no surprise that a rollout with a limited number of
trials follows exactly the same procedure. It's sufficient to say that
the proportion of wins/gammons etc. that come up when <span class="application">GNU
Backgammon</span> plays against itself (say) 1296 times, aren't
likely to vary all that much from the proportion we would get if we
measured the proportion of results in every game we could possibly get
of <span class="application">GNU Backgammon</span> playing against itself. (Of
course, there may still be some doubt whether the results of
<span class="application">GNU Backgammon</span> vs. <span class="application">GNU
Backgammon</span> are representative of the results of a
perfect player vs. a perfect player, or of you vs. Joe Average, but
that's another story.)</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="gnubg-rollouts_gnubg"></a>Rollouts in <span class="application">GNU Backgammon</span></h3></div></div></div><p>In <span class="application">GNU Backgammon</span> the Rollout function
implements the procedure described above, with the following
improvements:</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>Truncation: instead of rolling out all the way to the end of the
game, it can stop and pretend its evaluation after a few plies is
perfect. This may obviously introduce some amount of systematic
error, but in practice this may not matter because: </p></li><li class="listitem"><p>it makes rollouts much faster, which means you can do more of
them (and thus trade sampling error for systematic error); </p></li><li class="listitem"><p>different positions will be reached in different trials, so the
correlation between errors in each trial weakens and the errors
cancel out to some extent; </p></li><li class="listitem"><p>if you are rolling out the positions after making different
plays, then any remaining systematic error between the two rollouts
is likely to be somewhat correlated and so the error in the
comparison between the plays is hopefully small. This implies that
truncated rollouts are better for estimating
<span class="emphasis"><em>relative</em></span> equity (<span class="emphasis"><em>which is the better
move here, 13/10*/9 or 13/10* 6/5*?</em></span>) than
<span class="emphasis"><em>absolute</em></span> equity (<span class="emphasis"><em>at this match
score I need 29% wins to accept a dead cube; can I take in this
position?</em></span>). </p></li><li class="listitem"><p>Race database truncation: when the game enters its 2-sided
bearoff database, <span class="application">GNU Backgammon</span> can
estimate the probability of winning from that position with no error
at all (it can play and evaluate endgame positions perfectly), which
saves time and avoids introducing the errors that can result from
large equity variances at the end of the game. </p></li><li class="listitem"><p>Variance reduction: when using lookahead evaluations, it can
reduce errors by making use of the equity difference from one ply to
the next. (This can be interpreted as either canceling out the
estimated <span class="emphasis"><em>luck</em></span> (i.e. the difference in equity
evaluations before and after rolling) or using subsequent
evaluations to estimate the error in prior ones; the two views are
equivalent). <span class="application">GNU Backgammon</span> automatically
performs variance reduction when looking ahead at least one ply.
</p></li><li class="listitem"><p>Stratified sampling: uses quasi-random number generation instead
of pseudo-random number generation (this is a standard technique in
Monte Carlo simulations where having a near-perfect uniform
distribution in your sample is more important than
unpredictability). <span class="application">GNU Backgammon</span> only
stratifies the first 2 plies of a rollout, though it would be easy
enough to extend it to the remainder. </p></li></ol></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-rollouts_gnubg_quasi"></a>Quasi-Random Dice</h4></div></div></div><p>Quasi-Random Dice are used to reduce the element of luck in
rollouts. Instead of selecting purely random dice, <span class="application">GNU
Backgammon</span> will ensure a uniform distribution of the
first roll of the rollout. If 36 trials are requested, one game will
start with 11, two games with 21, two games with 31, etc. In general, if
n * 36 games is requested, n games will start with 11, 2*n games with 21
etc. This is called <span class="emphasis"><em>rotation</em></span> of the first roll.
Similarly, if n*1296 trials is requested, the second roll will be
rotated, such that n games will start with 11-11, n games with 11-21, n
games with 21-21, etc. The third roll be also be rotated if the number
of trials is proportional to 46656.</p><p>Suppose a user stops a 1296 trial rollout after 36 games. The 36
games would have had the following rolls for the first two rolls of each
game: 11-11, 21-11, 12-11, 31-11, 13-11, ..., 66-11 Obviously such a
rollout will give skewed results since the second roll was 11 for all
games! To avoid this problem <span class="application">GNU Backgammon</span>
will randomize the sequence of rolls such that it is guaranteed that for
any sample of 36 games you have exactly one game with first roll 11,
exactly one game with second roll 11, etc. This is called
<span class="emphasis"><em>stratification</em></span>.</p><p><span class="application">GNU Backgammon</span> will actually also rotate
and stratify rollouts where the number of trials are not multiples of
36, 1296, etc. The distribution of rolls is obviously not uniform any
longer in this case, but it will still provide some reduction of the
luck, i.e., no 37 trial rollout will have 3 games with a initial 66.</p><p>Before the first game of a rollout, <span class="application">GNU
Backgammon</span> creates a pseudo random array which it will use
for all the games in the rollout. In effect it has already decided the
roll sequence it will use for up to 128 rolls in every game of the
rollout. In other words, for a normal rollout where games don't go over
64 moves, every single game of every possible rollout length has already
had its dice sequence determined. During the rollout of game n, sequence
n will be used, for game n+1 sequence n+1, etc. If it's a
<span class="emphasis"><em>rollout as initial position</em></span>, then whenever the
current sequence starts with a double, the sequence is skipped and the
dice routine moves on to the next sequence. Say an <span class="emphasis"><em>rollout as
initial position</em></span> is about to start using sequence 275, but
that sequence begins with a double. The dice routine moves to sequence
276. On the following game, it will use sequence 277 (it remembers how
many it has already skipped).</p><p>So, if you select <span class="emphasis"><em>rollout as initial position</em></span>
and 36 games, then you will get a prefect set of rolls for games 1..30
and the first 6 rolls of the next perfect set (the same rolls you would
have gotten for games 31..36 if you'd asked for 1080 games or 10800
games or 92 games or whatever.</p><p>The dice sequence doesn't know how many trials it will be asked for,
it simply generates sequences such that for a normal rollout
(<span class="emphasis"><em>rollout as initial position</em></span>) every 36 (30) games
you get all possible 1st rolls, every 1296 (1080) games get every
possible first 2 rolls, every 46656 (38880) games you get full sets of 3
rolls, etc.</p></div></div></div><div class="sect1"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="gnubg-custom"></a>Customizing <span class="application">GNU Backgammon</span></h2></div></div></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="gnubg-custom_eval"></a>Evaluation settings</h3></div></div></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-custom_eval_intro"></a>Introduction to evaluation settings</h4></div></div></div><p><span class="application">GNU Backgammon</span> evaluation functionality
is driven by 3 separate neural networks. The neural nets evaluates
each position statically, and returns the outcome probabilities of the
game at the given position. However, there are several different
methods and techniques that an evaluation can use, and these can be
adjusted. It's possible to set different levels of lookahead, it's
possible to add noise to the evaluation, and each evaluation can be
done cubeful or cubeless. All these setting together form a total
<span class="emphasis"><em>evaluation setting</em></span>. In <span class="application">GNU
Backgammon</span> there are several of these evaluations
setting for each operation <span class="application">GNU Backgammon</span>
does.</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>Evaluation setting for Hints and Evaluations </p></li><li class="listitem"><p>Evaluation setting for analysis. </p></li><li class="listitem"><p>Evaluation setting for <span class="application">GNU
Backgammon</span> when it's playing. </p></li><li class="listitem"><p>Several evaluation settings for each move performed in a
rollout. </p></li></ol></div></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-custom_eval_depth"></a>The depth to search and plies</h4></div></div></div><p>A <span class="emphasis"><em>ply</em></span> is simply considered to be one turn by
a player. Any position can be evaluated at 0-ply. That means that GNU
Backgammon does not look ahead in the game to evaluate the position.
When GNU Backgammon is evaluating a checker play decision, it looks at
all resulting positions after all the legal moves with the given dice
roll, and evaluates these position at the given ply. It's possible to
set the search depth by specifying the plies lookahead in any
evaluation settings dialog.</p><p>Snowie users: <span class="application">GNU Backgammon</span> differs
from some other software, notably Snowie in that <span class="application">GNU
Backgammon</span> zero ply is the same as Snowie 1 ply. In
the same way what is called 2-ply in <span class="application">GNU
Backgammon</span> will therefore be similar to a Snowie 3-ply.</p><p>For <span class="application">GNU Backgammon</span>, a 0-ply evaluation
of a move would be done by:</p><p>Build a list of all legal moves. For each move, take the resulting
board position and use the neural net to estimate the expected
percentage of wins/gammons/backgammons/losses/gammon losses/backgammon
losses. Rank the moves based on this evaluation.</p><p>For one ply, after doing the above step, <span class="application">GNU
Backgammon</span> chooses the best n moves (where n is set by
the move filters). For each one, it takes the resulting position for
that move and goes through all 21 possible dice rolls for the
opponent. From these results, it works out the average expectation for
the initial move and ranks them. This is the same as Snowie 2 ply. You
can think of it as asking "what's my best move if I also consider
every possible dice roll and move my opponent might make?"</p><p>For 2 ply (Snowie 3 ply), a similar process is done, but this
time, not only are the opponents possible moves considered, but, for
each of these, the player on roll's next move will be considered as
well.</p><p>For a single move, on average there are about 20 legal moves to
consider.</p><p>When doing a one ply analysis/evaluation, for the top n moves
(from the move filter, <span class="application">GNU Backgammon</span> needs
to consider 21 rolls by the opponent, 20 and possible legal moves per
roll) = 420 positions to evaluate.</p><p>Every additional ply will multiply the previous number of
evaluations by about 400 odd, which explains the huge difference in
playing speed/analysis speed between 0 ply and 2 ply settings. I don't
think many people would enjoy playing against <span class="application">GNU
Backgammon</span> at 3 ply settings, where moves could take
minutes to be selected. It's also not clear that using much deeper
lookahead actually gains a lot in terms of playing strength - if you
really need better answers than 2 ply, rollouts are probably a lot
better.</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-custom_eval_define"></a>Defining evaluation settings</h4></div></div></div><p>First of all: There are several places in <span class="application">GNU
Backgammon</span> where you can adjust either it's skill at
playing or the quality of it's hints and analysis:</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-custom_eval_skill"></a>Playing skill:</h4></div></div></div><p><span class="guimenu">Settings</span> → <span class="guimenuitem">Players</span> → <span class="guimenuitem">Player 0</span> - choose Supremo or World Class. GNU Backgammon will
take longer choosing its moves, but they will be very strong. At this
setting, it is much stronger than Jellyfish level 7.</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-custom_eval_hint"></a>Hints:</h4></div></div></div><p><span class="guimenu">Settings</span> → <span class="guimenuitem">Evaluation</span> - choose Supremo or World Class if you want hints to be
very accurate, but, like the playing skill setting, you may find that
it can take as long as 15 seconds to get an answer on a 1GHz PC.
Expert will be very fast, but for some positions where you need to
consider what your opponent may do on his roll and how you will follow
it up, the results will be less accurate. A wild guess would be
somewhere around 2 or 3 percent of the time, World Class or stronger
settings would give a different best move and maybe less than 1/2
percent of the time, the Expert result would be seriously
wrong.</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-custom_eval_analysis"></a>Analysis:</h4></div></div></div><p><span class="guimenu">Settings</span> → <span class="guimenuitem">Analysis</span> - these settings are used by the Analyse Move/Game/Match
or Session command. Note that this is totally different to what is
used in the Hint command, which uses the above settings. You probably
want at least World Class here. My experience on a 700MHz PC is that a
7 point match takes about 15 to 20 minutes to analyse on the Supremo
settings. But the results tend to be very accurate.</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-custom_eval_rollout"></a>Rollouts:</h4></div></div></div><p><span class="guimenu">Settings</span> → <span class="guimenuitem">Rollouts</span> → <span class="guimenuitem">General Settings</span> tick the boxes for 'Cube decisions use same settings
same as checker play' and 'Use same settings for both players'</p><p><span class="guimenu">Settings</span> → <span class="guimenuitem">Rollouts</span> → <span class="guimenuitem">First Play Both</span> - select Expert here (this is my opinion). When doing
rollouts, most of the time Expert play will be more than strong enough
if you do say 1296 trials with no truncation. The rollout function has
an enormous number of options, most of which are only useful when
trying to investigate special positions. The simple expert setting for
both players is probably more accurate than any of the Analysis
functions. The downside is that rolling out 1296 trials of an early
move in a game can take a couple of hours. On World Class or Supremo
rollout settings, it can take more than 24 hours of computing
time.</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-custom_eval_dialog"></a>Changing evaluation settings</h4></div></div></div><p>A typical evaluation settings dialog is shown in this figure.</p><div class="figure"><a id="gnubg-fig_evaldialog"></a><p class="title"><strong>Figure 20. The evaluation settings dialog</strong></p><div class="figure-contents"><div class="mediaobject"><img src="images/evalsetting.png" alt="[[evalsettings.png]]" /></div></div></div><br class="figure-break" /><p>The dialog is consisting of two columns, the left column is for
setting the checker play decision evaluation settings, and the right
column is for setting the cube decision evaluation settings.</p><p>For each column you can select some predefined settings, or you
can define your own settings.</p><p>In the lookahead box, you can adjust the lookahead of each
evaluation by specifying the plies to be evaluated. Each ply costs
approximately a factor of 21 in computational time. Also note that
2-ply is equivalent to Snowie's 3-ply setting.</p><p>In the box for Cubeful evaluations, you can specify if you want
GNU Backgammon to evaluate the cube ownership in its evaluations.
With this option turned on it generally improves the evaluation,
specially when it's close to cube decisions, so we recommend that this
option is turned on.</p><p>In the Noise box, you can add noise to the evaluation. This can be
smart if you think the program plays to strong. You can use the Noise
box option to introduce noise or errors in the evaluations. This is
useful for introducing levels below 0-ply. The lower rated bots (e.g.,
GGotter) on the GamesGrid backgammon server uses this technique. The
introduced noise can be deterministic, i.e., always the same noise for
the same position, or it can be random.</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-custom_eval_predefined"></a>Predefined settings</h4></div></div></div><p>At the top of each evaluation settings column, it's possible to
set a predefined setting.</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>Beginner This setting uses no lookahead and add up to 0.060
noise to the evaluation. With this setting <span class="application">GNU
Backgammon</span> will evaluate like a beginner.</p></li><li class="listitem"><p>Casual play This setting uses no lookahead and add up to 0.050
noise to the evaluation. With this setting <span class="application">GNU
Backgammon</span> will evaluate a bit better than the
beginner setting but not much.</p></li><li class="listitem"><p>Intermediate This setting uses no lookahead and add up to
0.030 noise to each evaluation. It still plays a intermediate
game.</p></li><li class="listitem"><p>Advanced This setting uses no lookahead and add up to 0.015
noise to each evaluation. This setting plays a good game.</p></li><li class="listitem"><p>Expert This setting uses no lookahead but does not add any
noise to the evaluations. This settings play a strong game.
</p></li><li class="listitem"><p>World class This setting uses 2-ply lookahead, it uses no
noise and it uses a normal move filter. This plays a really
strong game, on par with the very best humans players.</p></li><li class="listitem"><p>Supremo This is basically the same as the World Class setting,
but it uses a larger move filter.</p></li><li class="listitem"><p>Grandmaster This setting uses 3-ply lookahead, no noise and
a large move filter. This setting is extremely strong and still
fast on current computers.</p></li><li class="listitem"><p>4ply This setting uses 4-ply lookahead, no noise and
a large move filter. This setting is extremely strong, but it's
also quite slow. It is more suitable to analysis than to actual play.</p></li></ol></div></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-custom_eval_filter"></a>Move filters</h4></div></div></div><div class="sect4"><div class="titlepage"><div><div><h5 class="title"><a id="gnubg-custom_eval_filter_intro"></a>Introduction to move filters</h5></div></div></div><p><span class="application">GNU Backgammon</span> uses a technique
called move filters in order to prune the complete list of legal
moves when analysing checker play decisions.</p><p>A move filter for a given ply, say, 2-ply, consists of four
parameters for each sub ply:</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>whether to analyse at all at this sub ply, </p></li><li class="listitem"><p>the number of moves always accepted at the given level,
</p></li><li class="listitem"><p>the number of extra moves to add, </p></li><li class="listitem"><p>the threshold for adding extra moves. </p></li></ol></div><p>A move filter for a given ply, say, 2-ply, consists of four
parameters for each sub ply:</p><p>whether to analyse at all at this sub ply, the number of moves
always accepted at the given level, the number of extra moves to
add, the threshold for adding extra moves. For example, for 2-ply
checker play decisions there are two move filters: one for pruning
at 0-ply, and another for pruning at 1-ply. The predefined setting
<span class="emphasis"><em>Normal</em></span> has: accept 0 moves and add up to 8
moves within 0.16 at 0-ply, and no pruning at 1-ply.</p><p>Consider the opening position where 4-2 has been rolled:</p><div class="figure"><a id="gnubg-fig_movefilter"></a><p class="title"><strong>Figure 21. Example of move filter settings</strong></p><div class="figure-contents"><div class="mediaobject"><img src="images/movefilterex.png" alt="[[movefilterex.png]]" /></div></div></div><br class="figure-break" /><p><span class="application">GNU Backgammon</span> starts by finding all
possible moves and evaluate those at 0-ply:</p><div class="informaltable"><table border="1"><colgroup><col /><col /><col /><col /><col /><col /></colgroup><tbody><tr><td>1.</td><td>Cubeful</td><td>0-ply</td><td>8/4 6/4</td><td>Eq.:+0.189</td><td> </td></tr><tr><td>2.</td><td>Cubeful</td><td>0-ply</td><td>24/20 13/11</td><td>Eq.:+0.046</td><td>(-0.143)</td></tr><tr><td>3.</td><td>Cubeful</td><td>0-ply</td><td>13/11 13/9</td><td>Eq.:+0.044</td><td>(-0.145)</td></tr><tr><td>4.</td><td>Cubeful</td><td>0-ply</td><td>24/22 13/9</td><td>Eq.:+0.034</td><td>(-0.155)</td></tr><tr><td>5.</td><td>Cubeful</td><td>0-ply</td><td>24/22 24/20</td><td>Eq.:-0.006</td><td>(-0.194)</td></tr><tr><td>6.</td><td>Cubeful</td><td>0-ply</td><td>24/18</td><td>Eq.:-0.009</td><td>(-0.198)</td></tr><tr><td>7.</td><td>Cubeful</td><td>0-ply</td><td>24/20 6/4</td><td>Eq.:-0.019</td><td>(-0.208)</td></tr><tr><td>8.</td><td>Cubeful</td><td>0-ply</td><td>13/9 6/4</td><td>Eq.:-0.024</td><td>(-0.213)</td></tr><tr><td>9.</td><td>Cubeful</td><td>0-ply</td><td>13/7</td><td>Eq.:-0.052</td><td>(-0.241)</td></tr><tr><td>10.</td><td>Cubeful</td><td>0-ply</td><td>24/20 8/6</td><td>Eq.:-0.053</td><td>(-0.242)</td></tr></tbody></table></div><p></p><p>According to the move filter the first 0 moves are accepted. The
equity of the best move is +0.189, and according to the move filter
we add up to 8 extra moves if they're within 0.160, that is, if they
have equity higher than 0.029. Moves 5 through 18 all have equity
lower that, so the move list after pruning at 0-ply consists of
moves 1 through 4. According to the move filter we do not perform
any pruning at 1-ply, so moves 1 through 4 are submitted for
evaluation at 2-ply;</p><div class="informaltable"><table border="1"><colgroup><col /><col /><col /><col /><col /><col /></colgroup><tbody><tr><td>1.</td><td>Cubeful</td><td>2-ply</td><td>8/4 6/4</td><td>Eq.:+0.180</td><td> </td></tr><tr><td>2.</td><td>Cubeful</td><td>2-ply</td><td>24/20 13/11</td><td>Eq.:+0.052</td><td>(-0.127)</td></tr><tr><td>3.</td><td>Cubeful</td><td>2-ply</td><td>13/11 13/9</td><td>Eq.:+0.043</td><td>(-0.137)</td></tr><tr><td>4.</td><td>Cubeful</td><td>2-ply</td><td>24/22 13/9</td><td>Eq.:+0.035</td><td>(-0.145)</td></tr><tr><td>5.</td><td>Cubeful</td><td>0-ply</td><td>24/22 24/20</td><td>Eq.:-0.006</td><td>(-0.185)</td></tr><tr><td>6.</td><td>Cubeful</td><td>0-ply</td><td>24/18</td><td>Eq.:-0.009</td><td>(-0.189)</td></tr><tr><td>7.</td><td>Cubeful</td><td>0-ply</td><td>24/20 6/4</td><td>Eq.:-0.019</td><td>(-0.199)</td></tr><tr><td>8.</td><td>Cubeful</td><td>0-ply</td><td>13/9 6/4</td><td>Eq.:-0.024</td><td>(-0.203)</td></tr><tr><td>9.</td><td>Cubeful</td><td>0-ply</td><td>13/7</td><td>Eq.:-0.052</td><td>(-0.232)</td></tr><tr><td>10.</td><td>Cubeful</td><td>0-ply</td><td>24/20 8/6</td><td>Eq.:-0.053</td><td>(-0.232)</td></tr></tbody></table></div><p></p><p>If we instead request a 4-ply checker play decision,
<span class="application">GNU Backgammon</span> will use the move
filters defined for 4-ply:</p><div class="informaltable"><table border="1"><colgroup><col class="c1" /><col class="c2" /><col class="c3" /><col class="c4" /></colgroup><tbody><tr><td>Ply</td><td>Accept moves</td><td>Extra moves</td><td>Threshold for extra moves</td></tr><tr><td>0</td><td>0</td><td>8</td><td>0.160</td></tr><tr><td>1</td><td>no pruning</td><td> </td><td> </td></tr><tr><td>2</td><td>0</td><td>2</td><td>0.040</td></tr><tr><td>3</td><td>no pruning</td><td> </td><td> </td></tr></tbody></table></div><p>The 4-ply move filter is identical to the 2-ply for pruning at
0-ply, so after 0-ply we have the same three moves as above. Since
there is no pruning at 1-ply these three moves are evaluated at
2-ply as above. There is no pruning at 3-ply.</p><p>At 4-ply we do not accept any moves, but add up to two moves if
there within 0.040 from the best move. Since the second best move is
-0.138 worse than the best move, we do not accept any moves to be
evaluated at 4-ply. Hence <span class="application">GNU Backgammon</span>
will actually not evaluate any moves on 4-ply.</p><p>The predefined move filters all have accept 0 moves, in order to
facilitate fast decisions and analysis, i.e., no need to waste much
time over obvious moves.</p><p>For post-mortem analysis it may be worthwhile to ensure that GNU
Backgammon analyses at least two moves at the specified ply. To do
this, specify accept 2 moves in the move filters you use for
analysis. However, do note that <span class="application">GNU
Backgammon</span> will force evaluation at the specified ply
if the actual move made is doubtful. This ensures that all errors
and blunders are evaluated at the same level.</p></div><div class="sect4"><div class="titlepage"><div><div><h5 class="title"><a id="gnubg-custom_eval_filter_define"></a>Defining move filters</h5></div></div></div><p>The move filter allows you to control exactly how many moves GNU
is examining at each ply. A ply is basically one move played by one
side, thus if both sides played a move, it would be one whole move,
but two plies, one for each side. To change the specific settings,
press the Modify... button.</p><p>Although the predefined levels, such as World Class, Supremo,
etc. are tested and good, you may want to know or control how GNU
filters its moves to analyse and how many.</p><div class="figure"><a id="gnubg-fig_movefilter1"></a><p class="title"><strong>Figure 22. Move filter 1</strong></p><div class="figure-contents"><div class="mediaobject"><img src="images/movefilter1.png" alt="[[movefilter1.png]]" /></div></div></div><br class="figure-break" /><p>If you are playing Expert level (this is what GGRaccoon is set
at) or another 0-ply setting, the Move Filter settings will not
change a thing, as Expert level automatically examines all moves. At
Supremo level, this changes though, as it takes a selection of the
best moves from 0-ply and examines them at 2-ply. This means that
for those selected moves it will calculate all the possibilities 2
plies ahead and evaluate them, allowing it to find better moves.
Since Supremo is a 2-ply setting, we are only interested in the
2-ply settings of Large as in the figure above. 3-ply or 4-ply
settings will have no effect here because Supremo doesn't examine at
that depth.</p><p>In the figure above, we can see it first will Always accept 0
moves. This first line means that it won't force any moves to be
analysed at 2-ply, it will only analyse moves according to the
second line. If it had said it would always analyse 2 moves, this
would mean that no matter how ridiculously bad the 2nd move was
compared to the 1st, it would analyse both at 2-ply.</p><p>The second line says it will Add extra 16 moves within 0.320.
This means that provided they aren't more than 0.320 equity worse
than the top move, it will select a maximum of 16 moves to analyse
at 2-ply. For example, in the figure below, the 2nd best move is no
less than 0.453 equity worse than the top choice, so it didn't
bother analysing them at 2-ply as it is unlikely to change its mind
on what the best move is.</p><div class="figure"><a id="gnubg-fig_movefilter2"></a><p class="title"><strong>Figure 23. Move filter 2</strong></p><div class="figure-contents"><div class="mediaobject"><img src="images/movefilter2.png" alt="[[movefilter2.png]]" /></div></div></div><br class="figure-break" /><p>Take a look at next figure.</p><div class="figure"><a id="gnubg-fig_movefilter3"></a><p class="title"><strong>Figure 24. Move filter 3</strong></p><div class="figure-contents"><div class="mediaobject"><img src="images/movefilter3.png" alt="[[movefilter3.png]]" /></div></div></div><br class="figure-break" /><p>Here, the exact same settings were maintained, but the 1-ply
filter was activated. This just means that those 16 moves selected
from the 0-ply are sent instead to be analysed at 1-ply, and then up
to 5 moves from 1-ply will be sent to be analysed at 2-ply. So this
would actually be faster than the previous setting (and weaker),
since a maximum of only 5 moves would be analysed at 2-ply depth.</p><p>Tip: Feel free to experiment with the settings, as you can
always reset them by simply choosing one of the predefined levels.
In order to see if they are better, or as good but faster, I'd
suggest comparing the results with Supremo. One setting I have that
works quite well, is to take the basic Supremo setting and in the
Move filter reduce the 16 to 12. It cuts down on the thinking time
by 20-25% more or less, and I haven't seen more than one case in
over 10,000 moves where it missed the best move.</p></div></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-eval_cubeful"></a>Cubeful vs Cubeless</h4></div></div></div><p>In the evaluation settings dialog box you can specify whether or
not checker play should be evaluated cubeful. It's recommended that
you use cubeful evaluation. To get an understanding of what cubeful
checker play evaluations are, you can take a look at this position:</p><div class="figure"><a id="gnubg-fig_cubeful"></a><p class="title"><strong>Figure 25. Cubeful example</strong></p><div class="figure-contents"><div class="mediaobject"><img src="images/cubeful-ex1.png" alt="[[cubeful-ex1.png]]" /></div></div></div><br class="figure-break" /><p>In this position black has rolled 51 and he has a good position.
If the position is evaluated cubeless the best move is 13/7. Black can
hope white does not roll 34 or 35 form the bar and has now a good
chance to close white out in the next few rolls. However if white
rolls one of the four hitting numbers from the bar, white will quite
soon have a really hot redouble. This redouble increases whites equity
so much that black actually should play this move safe. He should play
13/8 6/5. However if the evaluation was set to cubeless, an setting
which assumes white will never redouble, black should play 13/8.</p><p>Here's another example:</p><div class="figure"><a id="gnubg-fig_cubeful2"></a><p class="title"><strong>Figure 26. Cubeful example 2</strong></p><div class="figure-contents"><div class="mediaobject"><img src="images/cubeful-ex2.png" alt="[[cubeful-ex2.png]]" /></div></div></div><br class="figure-break" /><p>This is from a 5 point match where black has 1 point and white has
3 points. Black wins the opening roll and considers playing 13/11 6/5
or 24/23 13/11.</p><p>If <span class="application">GNU Backgammon</span> uses a cubeless
evaluation it will play 24/23 13/11. But if you're using a cubeful
evaluation it will play 13/11 6/5. Slotting with 6/5 is at this score
a better move even though it loses more gammons. The gammons black are
losing won't matter anyway, since black will turn the cube in the next
few rolls anyway. The slotting play also wins more gammons, and with
the cube tuned to 2, black should play towards gammonish positions at
this score.</p><p>You can read more about cubeful evaluations in the [[Appendix]].</p><p>It's recommended that you use cubeful checker evaluations.</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-custom_eval_pruning"></a>Pruning neural networks</h4></div></div></div><p>A feature in the evaluation is the use of a set of neural
networks just to prune away move candidates within a deeper ply
search. This increases the speed considerably and it doesn't lose much
playing strength compared to evaluation without these pruning neural
nets. Jim Segrave has just done an analysis of this and found that
less than 1% of all moves come out different with the pruning nets
activated. In most of these positions the move would not have made any
difference to the game at all.</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-custom_eval_noise"></a>Noise</h4></div></div></div><p>If you think <span class="application">GNU Backgammon</span> plays too
strong for you, you can add some noise to its evaluation. The number
you add into the field in the evaluations setting is the limit amount
of noise that will be added to the evaluation.</p><p>If noise is added to the evaluations <span class="application">GNU
Backgammon</span> will take a Box Müller transform of a point
in the unit circle and add to each possible outcome probability. This
means that the addition is random, but distributed so that it's more
likely to have an noise addition close to zero than a noise addition
close to the limit. The noise addition is limited to the number you
put into the noise field in the dialog box.</p><p>If you check the box Deterministic noise, the noise added to each
evaluation will be based on a sum of the bytes in the hash of the
board position, which (by the central limit theorem) should have a
normal distribution. In that way you will always have that same noise
amount to a position, since the noise added to the evaluation is only
depending on the position itself.</p><p>If you want <span class="application">GNU Backgammon</span> to evaluate
and play as strong as possible, you should not add any noise.</p></div></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="gnubg-custom_appearance"></a>Appearance</h3></div></div></div><p>You can change the appearance of <span class="application">GNU
Backgammon</span>. There is a lot of options to choose among and
you can have the board look like nearly anything. This section will help
you through some on the appearance customization.</p><p>To change the look of the board, you should click <span class="guimenu">Settings</span> → <span class="guimenuitem">Appearance</span>. This will open a dialog box like this:</p><div class="figure"><a id="gnubg-fig_appear"></a><p class="title"><strong>Figure 27. The appearance dialog</strong></p><div class="figure-contents"><div class="mediaobject"><img src="images/appearence.png" alt="[[appearance.png]]" /></div></div></div><br class="figure-break" /><p>In this dialog box you see a preview picture of the board at the
right side, and you have notebook with options to the left.</p><p>There are two different board rendering engines in <span class="application">GNU
Backgammon</span>. It's a 2 dimensional rendering engine which
is simple and fast, but still makes really good board images. The moves
can be animated.</p><p>The other board rendering type is a 3 dimensional board engine based
on OpenGL. This board rendering engine makes astonishing fine board
graphics, and animates the rolls and moves beautifully. You can even add
textures to your boards and checkers. However, the 3D rendering type
need a good modern graphic card which can take 3D hardware acceleration.</p><p>The leftmost tab in the appearance settings notebook is the General
option. You can here select between the 2D board or the 3D board. You
can also choose between different other settings. Most of the settings
here are self explanatory.</p><div class="warning" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Warning</h3><p>Don't forget to save your settings!! A lovely and painstakingly
crafted board setup can be lost if you don't faithfully do your <span class="guimenu">Settings</span> → <span class="guimenuitem">Save settings</span>.</p></div></div></div><div class="sect1"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="gnubg-technotes"></a>Technical Notes</h2></div></div></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="gnubg-tech_databases"></a>Obtaining bearoff databases</h3></div></div></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-tech_databases_generate"></a>Generate your own</h4></div></div></div><p><span class="application">GNU Backgammon</span> is supplied with a
program makebearoff that is used to generate bearoff databases. Due to
various limitations it is only possible to generate bearoff databases
with a size less than 2GB, i.e., the 13pt one-sided database and the
11 checker two-sided database are the largest databases that can be
generated with makebearoff. </p><p>To generate one sided database issue </p><p>makebearoff -o 10 -f gnubg_os.bd</p><p>to generate the one sided 10 point database. The program
makebearoff uses a cache to store previously generated positions. You
may set the cache size with the -s size option, e.g., </p><p>makebearoff -o 10 -s 123456789 -f gnubg_os.bd</p><p>to use 123,456,789 bytes of memory for cache size. In general, if
the cache size is less than the size of the database to be generated,
then extra time is needed to generate the bearoff database because
some positions may have to be calculated several times. </p><p>makebearoff can also reuse previously generated databases, so if
you already had generated the 9 point database you can reuse it: </p><p>mv gnubg_os.bd gnubg_os9.bd</p><p>makebearoff -o 10 -O gnubg_os9.bd -f gnubg_os.bd</p><p>Note that makebearoff requires temporary disk space to generate
both one sided and two sided databases. In general, twice the disk
space of the database to be generated is needed. </p><p>To generate a two sided database issue </p><p>makebearoff -t 6x8 -f gnubg_ts.bd</p><p>This example will generate the 8 checkers on 6 points database.
Again, it's possible to adjust the amount of memory with the -s
option. It's recommended to set the cache size to the maximum amount
of memory available (although there is no need to set it beyond the
size of the bearoff database to be generated). </p><p>Other options for makebearoff are available, see makebearoff
--help for the complete set. </p><p>The accompanying program makehyper is used to generate databases
for Hypergammon. For example, to generate the 3-checker database issue
the command </p><p>makehyper -c 3 -f hyper3.bd</p><p>Since the generation is <span class="emphasis"><em>very</em></span> time consuming
makehyper will generate a checkpoint file (in the example above:
hyper1.bd.tmp) that can be used to restart the calculation if needed
by using the -r option. You can also change the default convergence
threshold of 0.00001 if you're happy with less accurate equities. To
generate the 3 checker database you need approximately 400 MB of free
memory. On a 2.4 GHz box with 512 MB of RAM the calculation ran for 58
iterations of 3000 seconds each, i.e., a total of 48 hours! </p><p>See makehyper --help for the complete set of available options.
</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-tech_databases_download"></a>Download</h4></div></div></div><p>You may download the two sided database with 6 checkers on 6
points from <a class="ulink" href="ftp://alpha.gnu.org/gnu/gnubg/gnubg_ts0.bd.gz" target="_top">ftp://alpha.gnu.org/gnu/gnubg/gnubg_ts0.bd.gz</a> and the one
sided database with 15 checkers 6 points from <a class="ulink" href="ftp://alpha.gnu.org/gnu/gnubg/gnubg_os0.bd.gz" target="_top">ftp://alpha.gnu.org/gnu/gnubg/gnubg_os0.bd.gz</a>. </p><p>Larger databases are available for download from <a class="ulink" href="ftp://ftp.demon.nl/pub/Demon/games/gnubg/databases/" target="_top">ftp://ftp.demon.nl/pub/Demon/games/gnubg/databases/</a>. </p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-tech_databases_install"></a>Installation of the databases</h4></div></div></div><p>The databases's installation directory depends on where
<span class="application">GNU Backgammon</span> is installed on your system.
It is displayed by <span class="guimenu">Help</span> → <span class="guimenuitem">About GNU Backgammon</span> → <span class="guimenuitem">Evaluation Engine</span>.
</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-tech_databases_verify"></a>Verification of the databases</h4></div></div></div><p>To verify that your generated or downloaded bearoff database is
correct, the table below lists the MD5 checksums for a number of
possible databases. </p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-tech_databases_os"></a>One-sided bearoff databases (compressed)</h4></div></div></div><p>The table below contains the MD5 checksums for the compressed one
sided bearoff databases, i.e., databases generated with default
options. </p><div class="informaltable"><table border="1"><colgroup><col /><col /><col /></colgroup><tbody><tr><td>Checkers </td><td>Points </td><td>MD5 checksum </td></tr><tr><td>15 </td><td>1 </td><td>c789f049ec98ce4e307b471257999f39 </td></tr><tr><td>15 </td><td>2 </td><td>b6e61c1625ae4b3b164e93ab064192b9 </td></tr><tr><td>15 </td><td>3 </td><td>346dae6139ccb4b227c534373e5c52e4 </td></tr><tr><td>15 </td><td>4 </td><td>653255f5f9f22fd50277f7ff25b2a343 </td></tr><tr><td>15 </td><td>5 </td><td>2064f9a56b23117d053a573c96a92fa2 </td></tr><tr><td>15 </td><td>6 </td><td>3dc7b833c4670849cee00479a9e21b49 </td></tr><tr><td>15 </td><td>7 </td><td>67235c8e0ee152df5daf36cbeae5b3c2 </td></tr><tr><td>15 </td><td>8 </td><td>a4acbb5c7e9e1f08e561afe0af934e5c </td></tr><tr><td>15 </td><td>9 </td><td>9c4ddab4e51c3e668c9c97b8f8768dbc </td></tr><tr><td>15 </td><td>10 </td><td>81b3898f06bbd08ee8295a839251a10a </td></tr><tr><td>15 </td><td>11 </td><td>78ecb4be86dab6af8755ea4063d50fb6 </td></tr><tr><td>15 </td><td>12 </td><td>770fcff48894a96ebb2249343ef94866 </td></tr><tr><td>15 </td><td>13 </td><td>cc74b69a62f6e648936f533838a527a8 </td></tr><tr><td>15 </td><td>14 </td><td>not available </td></tr><tr><td>15 </td><td>15 </td><td>not available </td></tr><tr><td>15 </td><td>16 </td><td>not available </td></tr><tr><td>15 </td><td>17 </td><td>not available </td></tr><tr><td>15 </td><td>18 </td><td>not available </td></tr></tbody></table></div></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-tech_databases_ts"></a>Two-sided bearoff databases (with cubeless and cubeful equities)</h4></div></div></div><p>The table below contains the MD5 checksums for the default two
sided bearoff databases. </p><div class="informaltable"><table border="1"><colgroup><col /><col /><col /></colgroup><tbody><tr><td>Checkers </td><td>Points </td><td>MD5 checksum </td></tr><tr><td>1 </td><td>6 </td><td>7ed6f8e7fce16ea2b80e07a4a516653c </td></tr><tr><td>2 </td><td>6 </td><td>e9d760bf213841c285245ed757a52f4d </td></tr><tr><td>3 </td><td>6 </td><td>9d67da3db32ad4720cc38eecf9a67967 </td></tr><tr><td>4 </td><td>6 </td><td>9156f37032d1d4b0352a41186e632dfc </td></tr><tr><td>5 </td><td>6 </td><td>0db19ab08feae1feb33ddbd709479f62 </td></tr><tr><td>6 </td><td>6 </td><td>44b6040b49b46cb9dd2ce8caa947044d </td></tr><tr><td>7 </td><td>6 </td><td>9eb8b042d4d2ddf8d40e74a892745ad5 </td></tr><tr><td>8 </td><td>6 </td><td>fcdbbc80b7ef84ddc81b839d0f26bed1 </td></tr><tr><td>9 </td><td>6 </td><td>a11b2d410d51401143d05e73f9ffac15 </td></tr><tr><td>10 </td><td>6 </td><td>12dc70c86f356d06bc96ee38dee40c62 </td></tr><tr><td>11 </td><td>6 </td><td>not available </td></tr><tr><td>12 </td><td>6 </td><td>not available </td></tr><tr><td>13 </td><td>6 </td><td>not available </td></tr><tr><td>14 </td><td>6 </td><td>not available </td></tr><tr><td>15 </td><td>6 </td><td>not available </td></tr></tbody></table></div></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-tech_databases_hyper"></a>Two-sided databases for Hypergammon</h4></div></div></div><p>As the generation of the Hypergammon databases are an iterative
process it's not possible to give MD5 checksum for these, as it depend
heavily on your convergence threshold, the number of restarts, and
rounding errors. </p><p>A random position from the database is found in <a class="xref" href="#gnubg-hypergammon" title="Example 2. Random position from hypergammon database">Example 2, “Random position from hypergammon database”</a>. The equities and
percentages in your own database should be very similar (if not
identical): </p><p><span class="application">GNU Backgammon</span> Position ID:
ADAAAQAkIAAAAA</p><div class="example"><a id="gnubg-hypergammon"></a><p class="title"><strong>Example 2. Random position from hypergammon database</strong></p><div class="example-contents"><pre class="programlisting">
GNU Backgammon Position ID: ADAAAQAkIAAAAA
Match ID : cAkAAAAAAAAA
+13-14-15-16-17-18------19-20-21-22-23-24-+ O: gnubg
| X X | | X | 0 points
| | | |
| | | |
| | | |
| | | |
v| |BAR| | (Cube: 1)
| | | |
| | | |
| | | |
| O | | | On roll
| O | | O | 0 points
+12-11-10--9--8--7-------6--5--4--3--2--1-+ X: jth
Player Opponent
Position 3018 2831
Owned cube : -0.0230
Centered cube : -0.2310
Centered cube (Jacoby rule) : -0.2186
Opponent owns cube : -0.3548
Win W(g) W(bg) L(g) L(bg) Equity (cubeful)
static: 0.456 0.244 0.014 0.318 0.019 (-0.168 (-0.219))
No double : -0.219
Double, pass : +1.000 (+1.219)
Double, take : -0.710 (-0.491)
Correct cube action: No double, beaver
</pre></div></div><br class="example-break" /></div></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="gnubg-tech_met"></a>Match Equity Tables</h3></div></div></div><p>Multiple match equity tables are bundled with <span class="application">GNU
Backgammon</span>, although most of them are only of marginal
or historical interest.</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><span class="emphasis"><em>Rockwell-Kazaross</em></span> or
<span class="emphasis"><em>Kazaross-XG2</em></span> are the recommended choice.
They were created by rolling out the initial position for every score
up to -15:-15 and are the best currently available estimations
of the match equities for a strong bot playing itself.
</li><li class="listitem"><span class="emphasis"><em>g11</em></span>, <span class="emphasis"><em>snowie</em></span> and
<span class="emphasis"><em>woolsey</em></span> are the tables that were used by earlier
versions of <span class="application">GNU Backgammon</span>,
<span class="application">Snowie</span> or for hand calculations back when
bots didn't do match equity calculations (or there was no bot at all).
All of them are now considered obsolete. Analyses or rollouts using
them can still be found in books, magazines or web sites so it can
occasionally be interesting to use them in
<span class="application">GNU Backgammon</span>
for comparison to these older results.
</li><li class="listitem"><span class="emphasis"><em>jacobs</em></span>, <span class="emphasis"><em>jac050</em></span> and
<span class="emphasis"><em>jac100</em></span> are from the book
<span class="emphasis"><em>_Can a Fish Taste Twice as Good_</em></span> by Jake Jacobs and
Walter Trice and give match equities if players are of equal strength, if
one is 50 Elo points stronger and if one is 100 points stronger
respectively.
They should only be used to analyse such unequal opponents situations.
</li><li class="listitem">
The other tables are obsolete and of no practical use.
</li></ul></div></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="gnubg-tech_python"></a>Python scripting</h3></div></div></div><p>Accessing the <span class="application">GNU Backgammon</span> Python shell</p><p>To access the Python shell, either type `>' from the command
line or select <span class="guimenu">Window</span> → <span class="guimenuitem">Python Shell(IDLE...)</span> from the GUI. </p><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-tech_python_module"></a>gnubg module functions</h4></div></div></div><p>board()</p><p>command(cmd)</p><p>evaluate()</p><p>evalcontext()</p><p>eq2mwc()</p><p>mwc2eq()</p><p>cubeinfo()</p><p>met()</p><p>positionid()</p><p>positionfromid()</p><p>positionkey()</p><p>positionfromkey()</p><p>positionbearoff()</p><p>positionfrombearoff()</p><p>navigate([next=N,[game=N]])</p><p>Match navigation. </p><p>Without any arguments, go to first move of first match. </p><p>With next == N, move forward N game records. </p><p>With game == N, move forward/backward N games. </p><p>Navigate never wraps around. </p><p>On success, returns None. If unable to complete the requested
number of moves, returns a pair of (next-remaining,game-remaining). </p><p>match([analysis=1/0, boards=1/0, statistics=0/1, verbose=0/1])</p><p>Return the current match. For example, </p><p>> m = gnubg.match()</p><p>Takes the following optional keyword arguments: </p><p>analysis</p><p>When 0, discard analysis data. default is 1. </p><p>boards</p><p>When 1, add current board to move/double records. Default is 1. </p><p>statistics</p><p>When 1, include game and match statistics. Default is 0. </p><p>verbose</p><p>When 1, include derived analysis values. Default is 0. </p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-tech_python_match"></a>Match description</h4></div></div></div><p>gnubg.match() returns a dictionary containing the following items: </p><p>match-info</p><p>General match info </p><p>games</p><p>A sequence, one element per game.</p><p>stats (optional)</p><p>Match statistics. </p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-tech_python_matchinfo"></a>Match info</h4></div></div></div><p>A dictionary containing the following items: </p><p>match-length </p><p>variation</p><p>One of Standard,Nackgammon, Hypergammon1, Hypergammon2 or
Hypergammon3. </p><p>rules (optional)</p><p>Additional rules used. A subset of NoCube, Crawford and Jacoby. </p><p>X</p><p>O</p><p>Per player information. Each a dictionary containing rating and
name. </p><p>annotator (optional)</p><p>round (optional)</p><p>place (optional)</p><p>date (optional)</p><p>Sequence of (Day,Month,Year). </p><p>event (optional)</p><p>default-eval-context</p><p>Default evaluation context. A dictionary in the same format as
returned by evalcontext(). </p><p>default-rollout-context</p><p>Default rollout context. </p><p>Example, </p><p>>>> m['match-info']</p><p>{'match-length': 25, 'rules': ('Crawford',),
'default-eval-context': {'plies': 2, 'deterministic': 1,
'noise': 0.0, 'cubeful': 1}, 'annotator': 'GNU 0.14', 'O': {'rating':
'0 (Exp 0)', 'name': 'Moshe Tissona'}, 'round': 'Final', 'place':
'Monte Carlo', 'variation': 'Standard', 'default-rollout-context':
{'n-truncation': 11, 'initial-position': 0, 'trials': 0,
'stop-on-std': 0, 'variance-reduction': 1, 'late-eval': 0,
'truncated-rollouts': 0, 'truncate-bearoff2': 1, 'cubeful': 1,
'truncate-bearoffOS': 1, 'seed': 1177750272, 'quasi-random-dice': 1,
'minimum-games': 144}, 'date': (13, 7, 2003), 'X': {'rating': '0 (Exp
0)', 'name': 'Jon Royset'}, 'event': 'World Championship 2003'}</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-tech_python_game"></a>Python game</h4></div></div></div><p>A dictionary containing the following items: </p><p>info</p><p>General game info. For example, </p><p>>>> m['games'][0]['info']</p><p>{'points-won': 1, 'score-X': 0, 'score-O': 0, 'winner': 'X',
'resigned': False}</p><p>If no winner is specified, winner is None. </p><p>>>> m['games'][2]['info']</p><p>{'score-X': 2, 'winner': None, 'score-O': 0}</p><p>game</p><p>A Sequence of actions.</p><p>stats (optional)</p><p>Game statistics. Similar entries to <span class="guimenu">Analyse</span> → <span class="guimenuitem">Game statistics</span> from the GUI. </p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-tech_python_gameaction"></a>Game actions</h4></div></div></div><p>Each action is a dictionary </p></div></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="gnubg-tech_equities"></a>Equities explained</h3></div></div></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-tech_equities_intro"></a>Introduction to equities</h4></div></div></div><p><span class="application">GNU Backgammon</span> works with many
different kinds of equities. The equity is defined as the expected
value of the position. However, this value can be expressed in several
different metrics and may be calculated with or without taking the
effect of the cube into consideration. In the following section we
will describe the equities used and calculated by GNU
Backgammon.</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-tech_equities_money"></a>Money equity</h4></div></div></div><p>This is the value of the position in money game, e.g., if your
equity is +0.4 an you are playing money game with a $1 stake, you will
win $0.40 on average. The money equity can be calculated with or
without taking the effect of the doubling cube into consideration, or
<span class="emphasis"><em>cubeful</em></span> or <span class="emphasis"><em>cubeless</em></span>. The
cubeless equity can be calculated from the basic formula:
2*p(w)-1+2(p(wg)-p(lg))+3(p(wbg)-p(lbg)). Evaluating the cubeful
equity is much more difficult; it can either be estimated from the
cubeless equity by using transformations as outlined by Rick Janowski
or by constructing a neural net that directly outputs cubeful
equities. GNU Backgammon uses the former approach (<a class="xref" href="#gnubg-tech_equities_cubeful" title="Cubeful equities">the section called “Cubeful equities”</a>).</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-tech_equities_match"></a>Match Winning Chance</h4></div></div></div><p>In match play we're generally not particular interested in the
outcome of the individual games as much as the outcome of the entire
match, so the interesting quantity for match play is <span class="emphasis"><em>match
winning chance</em></span> (MWC). As for the money equity the MWC can
be calculated with and without the effect of the doubling cube. The MWCs
are generally calculated with the use of a match equity table, which
contains the chance of winning the match before a game starts, e.g.,
if the score is 0-0 in a 1pt match each player has 50% chance of
winning the match before the game starts assuming they're of equal
skill.</p><p>The cubeless MWC is calculated as: MWC(cubeless) = p(w) * MWC(w) +
p(l) * MWC(l) + p(wg) * MWC(wg) + p(lg) * MWC(lg) + p(wbg) * MWC(wbg)
* p(lbg) * MWC(lbg).</p><p>For example, if the w/g/bg distribution is 0 30 60 - 40 10 0 and
the match score is 1-3 to 5 with the cube on 2 the cubeless MWC is:</p><p>MWC(cubeless)= 30% * 50% + 30% * 0% + 30% * 100% + 10% * 0% + 0% *
100% + 0% * 0% = 45%,</p><p>so the cubeless MWC is 45%.</p><p>Evaluating the cubeful MWC is more difficult, and as for the
cubeful money equity it's possible to estimate cubeful MWCs from
transformation on the w/g/bg distribution or directly calculate it
from neural nets. GNU Backgammon uses the former approach, but the
formula are currently not published.</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-tech_eq_norm"></a>Normalized equity</h4></div></div></div><p>It's generally very difficult to compare MWCs. For example, it's
hardly worth mentioning a 0.5% MWC error at DMP where as it's a huge
error at 0-0 to 7. It is therefore of interesting to normalize the
MWCs to some common scale. The most often used normalization is
Normalized Money Game Equity (NEMG) where the MWC for any game is
transformed into the same interval as money game, i.e., -3 to +3 (due
to anomalies at certain match scores the NEMG can go below -3 and
above +3). The transformation is linear:</p><p>NEMG = 2 * (MWC-MWC(l))/(MWC(w)-MWC(l)) - 1</p><p>In other words, extrapolation with the following two extrapolation
points: (MWC(w),+1) and (MWC(l),-1).</p><p>For example, suppose the score is 3-1 to 5 with the cube on 2:
MWC(l)=0% and MWC(w)=50%:</p><div class="informaltable"><table border="1"><colgroup><col class="c1" /><col class="c2" /><col class="c3" /></colgroup><tbody><tr><td>MWC</td><td>NEMG</td><td class="auto-generated"> </td></tr><tr><td>0%</td><td>-1</td><td class="auto-generated"> </td></tr><tr><td>25%</td><td>0</td><td class="auto-generated"> </td></tr><tr><td>50%</td><td>+1</td><td class="auto-generated"> </td></tr><tr><td>75%</td><td>+2</td><td class="auto-generated"> </td></tr><tr><td>100%</td><td>+3</td><td class="auto-generated"> </td></tr></tbody></table></div><p>Note that a w/g/bg distribution of 0 100 100 - 0 0 0 gives a NEMG
of +3 whereas the corresponding money equity is only +2. This is
because the gammon price is high for that particular score. When both
players are far from winning the match, e.g., 0-0 to 17 or 1-0 to 17,
NEMG is very close to the usual money equity.</p><p>NEMG can be calculated from both cubeless and cubeful MWCs.</p><p>A word of caution: A cubeless NEMG calculated from a cubeless MWC
could be named <span class="emphasis"><em>cubeless equity</em></span>, but in most
backgammon literature this term seems to be reserved for the cubeless
money equity.</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-tech_equities_cubeful"></a>Cubeful equities</h4></div></div></div><p>This chapter is a brief description of how <span class="application">GNU
Backgammon</span> calculates cubeful equities. The formula
build directly on the work by Rick Janowski <a class="ulink" href="http://www.bkgm.com/articles/Janowski/cubeformulae.pdf" target="_top">Take-Points in Money Games</a> from 1993.</p><div class="sect4"><div class="titlepage"><div><div><h5 class="title"><a id="gnubg-tech_equities_cubeful_basic"></a>Basic formula for cubeful equities</h5></div></div></div><p>The basic formula for cubeful equities as derived by Janowski is</p><p>E(cubeful) = E(dead) * (1-x) + E(live) * x,</p><p>where E(dead) is the dead cube equity (cubeless equity) calculated
from the standard formula. E(live) is the cubeful equity assuming a
fully live cube. We'll return to that in the next section. x is the
cube efficiency. x=0 gives E(cubeful)=E(dead) as one extreme and x=1
gives E(cubeful)=E(live) as the other extreme. In reality x is
somewhere in between, which typical values around 0.6 - 0.8.</p><p>Janowski's article doesn't mention cubeful equities, so we use the
straightforward generalization</p><p>MWC(cubeful) = MWC(dead) * (1-x) + MWC(live) * x.</p><p>as MWC is the entity that is used for match play
evaluations.</p></div><div class="sect4"><div class="titlepage"><div><div><h5 class="title"><a id="gnubg-tech_equities_cubeful_live"></a>Live cube equities</h5></div></div></div><p>The live cube equity is the equity assuming that the equity
changes continuously, so that doubles and takes occurs exactly at the
double point and take point. For gammon-free play this is the
well-known take point of 20%. Janowski derives the more general
formula</p><p>TP = (L-0.5)/(W+L+0.5)</p><p>where W is the average cubeless value of games ultimately won, and
L is the average cubeless value of games ultimately lost. For example,
for the following position</p><div class="figure"><a id="gnubg-fig_cubeful1A"></a><p class="title"><strong>Figure 28. Cubeful example 1</strong></p><div class="figure-contents"><div class="mediaobject"><img src="images/cubefuleq-ex1.png" alt="[[cubefuleq-ex1.png]]" /></div></div></div><br class="figure-break" /><p><span class="application">GNU Backgammon</span> evaluates</p><div class="informaltable"><table border="1"><colgroup><col class="c1" /><col class="c2" /><col class="c3" /><col class="c4" /><col class="c5" /><col class="c6" /></colgroup><tbody><tr><td> </td><td>Win</td><td>W(g)</td><td>W(bg)</td><td>L(g)</td><td>L(bg)</td></tr><tr><td>static:</td><td>0.454</td><td>0.103</td><td>0.001</td><td>0.106</td><td>0.003</td></tr></tbody></table></div><p>and hence W=(0.454 + 0.103 + 0.001)/0.454=1.229 and
L=(0.556+0.106+0.003)/0.556) = 1.196. For gammon-free positions, e.g.,
a race, W=1 and L=1.</p><p>The live cube equity is now based on piecewise linear
interpolation between the points (0%,-L), (TP,-1), (CP,+1), and
(100%,+W): if my winning chance is 0 I lose L points, at my take point
I lose 1 point, at my cash point I cash 1 point, and when I have a
certain win I win W points:</p><div class="figure"><a id="gnubg-fig_mgtp"></a><p class="title"><strong>Figure 29. mgtp</strong></p><div class="figure-contents"><div class="mediaobject"><img src="images/mgtp.png" alt="mgtp" /></div></div></div><br class="figure-break" /><p>For match play there is no simple formula, since redoubles can
only occur a limited number of times.</p><p>The live cube take point is generally calculated as</p><p>TP(live, n Cube)=TP(effective, n cube) * (1 - TP(live, 2n cube))</p><p>So to calculate the live cube take points for a 1-cube at 3-0 to 7
we need the live cube take points for the 4-cube and the 2-cube. For
the position above and using Woolsey's match equity table the live
cube take point are:</p><div class="informaltable"><table border="1"><colgroup><col class="c1" /><col class="c2" /><col class="c3" /></colgroup><tbody><tr><td>Cube value </td><td>TP for Black </td><td>TP for White</td><td> </td><td> </td></tr><tr><td>4</td><td>0%</td><td>41%</td></tr><tr><td>2</td><td>15%</td><td>38.5%</td></tr><tr><td>1</td><td>24.5%</td><td>27.3%</td></tr></tbody></table></div><p>The calculation of these are left as an exercise to the reader.</p><p>Ignoring backgammons, the gammon rates for White and Black are
0.106/54.6=19% and 0.103/0.454=22%, respectively. If White wins the
game his MWC will be</p><p>81% * MWC(-3,-7) + 19% * MWC(-2,-7) = 78%</p><p>and if Black wins his MWC will be</p><p>78% * MWC(-4,-6) + 22% * MWC(-4,-5) = 41%.</p><p>If White cashes 1 point he has MWC(-3,-7)=76% and if Black cashes
he has MWC(-4,-6)=36%. Analogous to money game the live cube MWC is
calculated as piecewise linear interpolation between (0%,22%),
(24.5%,24%), (72.7%,36%), and (100%,41%) (from black's point of view):</p><div class="figure"><a id="gnubg-fig_mptp"></a><p class="title"><strong>Figure 30. mptp</strong></p><div class="figure-contents"><div class="mediaobject"><img src="images/mptp.png" alt="mptp" /></div></div></div><br class="figure-break" /></div><div class="sect4"><div class="titlepage"><div><div><h5 class="title"><a id="gnubg-tech_equities_cubeful_0ply"></a>0-ply Cubeful equities</h5></div></div></div><p>Having established the live cube equities and MWCs we're now in
position to calculate the 0-ply cubeful equities.</p><p>Let's start with money game: the cubeless equity is -0.097 and the
live cube equity can be determined from the figure above as -0.157.
Thus, the cubeful equity is -0.138.</p><p>For the match play example at the score 3-0 the cubeless MWC is
29.1% and from the figure Black using wins=45.4% we can determine the
live cube MWC to be 29.2%. Using a value of x=0.68 we arrive at a
cubeful MWC of 29.17%.</p></div><div class="sect4"><div class="titlepage"><div><div><h5 class="title"><a id="gnubg-tech_equities_cubeful_nply"></a>n-ply Cubeful equities</h5></div></div></div><p>The previous section concerned the calculation of 0-ply cubeful
equities, so how so <span class="application">GNU Backgammon</span>
calculate cubeful 2-ply equities? The answer is: by simple recursion:</p><p>Equity=0</p><p>Loop over 21 dice rolls</p><p>Find best move for given roll</p><p>Equity = Equity + Evaluate n-1 ply equity for resulting position</p><p>End Loop</p><p>Equity = Equity/36</p><p>Note that evaluating the n-1 ply equity involves a cube decision,
since the opponent may double, so <span class="application">GNU
Backgammon</span> will actually calculate the two n-1 ply
equities: (a) assuming no double, and (b) assuming double, take. These
two equities are combined with the equity for a pass, and the optimum
of these three is added to the resulting equity. For a cubeful 2-ply
evaluation <span class="application">GNU Backgammon</span> will end up
calculating the following cubeful 0-ply equities: centered 1-cube,
opponent owns 2-cube, owned 4-cube, and opponent owns 8-cube.</p><p>Note that the 2-ply level does not use the cube efficiency, it's
not used until at the 0-ply level, but it's possible to calculate an
effective one by isolating x in the basic cube formula:</p><p>x(eff) = (E(2-ply cubeful) - E(2-ply dead))/(E(2-ply live)-E(2-ply
dead)).</p></div><div class="sect4"><div class="titlepage"><div><div><h5 class="title"><a id="gnubg-tech_equities_cubeful_efficiency"></a>The cube efficiency</h5></div></div></div><p>The cube efficiency is obviously an important parameter,
unfortunately there haven't been much investigation carried out, so
<span class="application">GNU Backgammon</span> basically uses the values
0.6-0.7 originally suggested by Rick Janowski:</p><div class="informaltable"><table border="1"><colgroup><col class="c1" /><col class="c2" /></colgroup><tbody><tr><td>Position Class </td><td>x (Cube efficiency)</td><td> </td></tr><tr><td>Two-sided (exact) bearoff</td><td>n/a</td></tr><tr><td>One-sided bearoff</td><td>0.6</td></tr><tr><td>Crashed</td><td>0.68</td></tr><tr><td>Contact</td><td>0.68</td></tr><tr><td>Race</td><td>linear interpolation between 0.6 and 0.7</td></tr></tbody></table></div><p>For race <span class="application">GNU Backgammon</span> uses linear
interpolation based on pip count for the player on roll. A pip count
of 40 gives x=0.6 and 120 gives x=0.7. If the pip count is below 40 or
above 120 values of x=0.6 and x=0.7 are used, respectively.</p><p>For the two sided bearoff positions the cubeful money equity is
already available from the database, so for money game there is no
need to calculate cubeful equities via Janowski's formula. However,
the cubeful equities for money game cannot be used for match play.
Instead of using a fixed value of x, say, 0.6, <span class="application">GNU
Backgammon</span> will calculate an effective value based on
the cubeful money equity. The cubeful MWC is calculated as usual, but
with the calculated x.</p><p>There is obviously room for improvements. For example, holding
games should intuitively have a lower cube efficiency, since it's very
difficult to double effectively: either it's not good enough or you've
lost the market by a mile after rolling a high double or hitting a
single shot. Similarly, backgames will often have a low cube
efficiency, whereas blitzes have may have a higher cube
efficiency.</p></div><div class="sect4"><div class="titlepage"><div><div><h5 class="title"><a id="gnubg-tech_equities_cubeful_decisions"></a>Cube decisions</h5></div></div></div><p><span class="application">GNU Backgammon</span>'s cube decisions are
simple based on calculations of cubeful equities. For a double
decision <span class="application">GNU Backgammon</span> calculates the
cubeful equity for <span class="emphasis"><em>no double</em></span> and the cubeful
equity for <span class="emphasis"><em>double, take</em></span>. Combined with the equity
for <span class="emphasis"><em>double, pass</em></span>, it's possible to determine the
correct cube action.</p><p>The figure below shows the relevant cubeful equities for White and
black's cube decisions in sample position from earlier.</p><div class="figure"><a id="gnubg-fig_mgcd"></a><p class="title"><strong>Figure 31. mgcd</strong></p><div class="figure-contents"><div class="mediaobject"><img src="images/mgcd.png" alt="mgcd" /></div></div></div><br class="figure-break" /><p>On 0-ply Black will double when the green curve (White owns
2-cube) is above the red curve (centered cube), and White will take as
long as the green curve is below 1. Similarly, White will double when
the blue curve (Black owns 2-cube) is below the red curve (centered
cube), and Black takes as long as the blue curve is above -1.</p><p>Note that <span class="application">GNU Backgammon</span> doesn't
calculate the take point or double point explicitly. The cube decision
is simply made by comparing equities from the figure.</p></div><div class="sect4"><div class="titlepage"><div><div><h5 class="title"><a id="gnubg-tech_equities_cubeful_beyond"></a>Beyond the simple model</h5></div></div></div><p>Janowski has developed two other models for cubeful equities. The
first is a generalization of the one used by <span class="application">GNU
Backgammon</span>; it introduces two cube efficiencies
instead of one. Often you may see that the cube efficiencies are
different for the two players, and the <span class="emphasis"><em>refined general
model</em></span> as it is named by Janowski, tries to take this into
consideration by using different cube efficiency parameters for the
two players. For example, the blitzer may have another cube efficiency
that the blitzee.</p><p>The second model is not published, but redefines the cube
efficiency into a value that can be understood more intuitively and
calculate easily from rollouts.</p></div></div></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="gnubg-tech_postionid"></a>A technical description of the Position ID</h3></div></div></div><p>This section describes a method for compactly recording a
backgammon position. It demonstrates how to encode a position into
10 binary bytes, which is useful for minimizing the space used when
recording large numbers of positions in memory or on disk. There is
also an ASCII representation in 14 characters, which is convenient
for output to the screen, for copying and pasting to transfer
positions between programs which support the format, and for
communicating positions via Usenet news or e-mail. The 10 byte
binary format is called the key, and the 14 character ASCII format
is the ID.</p><p>The key is essentially a bit string (imagine you start with an
empty sequence of bits, and continue adding either
<span class="emphasis"><em>0</em></span> or <span class="emphasis"><em>1</em></span> to the end). The
way to build up a sequence that corresponds to a given position is:</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>For every point around the board (starting at the ace point
of the player on roll, continuing around to the 24 point and
ending at the bar): </p></li><li class="listitem"><p>append as many 1s as the player not on roll
(the opponent) has on that point (if any). </p></li><li class="listitem"><p>append a 0. </p></li><li class="listitem"><p>For every point around the board (starting at the ace point
of the opponent, continuing around to the opponent's 24 point
and ending at the bar): </p></li><li class="listitem"><p>append as many 1s as the the player on roll has
on that point (if any). </p></li><li class="listitem"><p>append a 0. </p></li><li class="listitem"><p>Pad out the string to 80 bits with 0s. </p></li></ol></div><p>The worst-case representation will require 80 bits: you can see
that there are always 50 0 bits even if there are no checkers at
all. Each player has a maximum of 15 checkers in play (not yet borne
off) which require a 1 bit wherever they are positioned. That's 30
bits to take of all checkers, plus the 50 bits of overhead for a
total of 80 bits (the last bit is always 0 and isn't strictly
necessary, but it makes the code slightly easier). This bit string
should be stored in little-endian order when packed into bytes (i.e.
the first bits in the string are stored in the least significant
bits of the first byte).</p><p>As an example, here's what the starting position looks like in
the key format:</p><div class="informaltable"><table border="1"><colgroup><col class="c1" /><col class="c2" /></colgroup><tbody><tr><td>0 0 0 0 0</td><td>opponent has no checkers on his ace to 5 points</td></tr><tr><td>11111 0</td><td>5 checkers on the 6 point</td></tr><tr><td>0</td><td>empty bar</td></tr><tr><td>111 0</td><td>3 on the 8</td></tr><tr><td>0 0 0 0</td><td>no others in his outfield</td></tr><tr><td>11111 0</td><td>5 on the midpoint</td></tr><tr><td>0 0 0 0 0</td><td>none in our outfield</td></tr><tr><td>0 0 0 0 0</td><td>or in our board, until...</td></tr><tr><td>11 0</td><td>two on the 24 point</td></tr><tr><td>0</td><td>none on the bar</td></tr><tr><td>0 0 0 0 0</td><td>player on roll has no checkers on his ace to 5 points</td></tr><tr><td>11111 0</td><td>5 checkers on the 6 point</td></tr><tr><td>0</td><td>empty bar</td></tr><tr><td>111 0</td><td>3 on the 8</td></tr><tr><td>0 0 0 0</td><td>no others in his outfield</td></tr><tr><td>11111 0</td><td>5 on the midpoint</td></tr><tr><td>0 0 0 0 0</td><td>none in opponent's outfield</td></tr><tr><td>0 0 0 0 0</td><td>or in opponent's board, until...</td></tr><tr><td>11 0</td><td>two on the 24 point</td></tr><tr><td>0</td><td>none on the bar</td></tr></tbody></table></div><p>so altogether it's:</p><p>00000111110011100000111110000000000011000000011111001110000011111000000000001100</p><p>In little endian bytes it looks like:</p><div class="informaltable"><table border="1"><colgroup><col class="c1" /><col class="c2" /><col class="c3" /><col class="c4" /><col class="c5" /><col class="c6" /></colgroup><tbody><tr><td>11100000</td><td>01110011</td><td>11110000</td><td>00000001</td><td>00110000</td><td>11100000</td><td>01110011</td><td>11110000</td><td>00000001</td><td>00110000</td></tr><tr><td>0xE0</td><td>0x73</td><td>0xF0</td><td>0x01</td><td>0x30</td><td>0xE0</td><td>0x73</td><td>0xF0</td><td>0x01</td><td>0x30</td></tr></tbody></table></div><p>so the 10 byte key (in hex) is E0 73 F0 01 30 E0 73 F0 01
30.</p><p>The ID format is simply the <a class="ulink" href="http://www.ietf.org/rfc/rfc2045.txt" target="_top">Base64</a> encoding
of the key. (Technically, a Base64 encoding of 80 binary bits should
consist of 14 characters followed by two = padding characters, but
this padding is omitted in the ID format.)</p><p>To continue the above example, splitting the 10 8-bit bytes into
14 6-bit groups gives:</p><p>111000 000111 001111 110000 000000 010011 000011 100000 011100
111111 000000 000001 001100 000000</p><p>In Base64 encoding, these groups are respectively represented
as:</p><p>4 H P w A T D g c / A B M A</p><p>So, the position ID of the checkers at the start of the game is
simply:</p><p>4HPwATDgc/ABMA</p><p>You can set the board in gnubg either by writing the position ID
into the position text input field in the GUI or by executing the
command</p><p>set board 4HPwATDgc/ABMA.</p><p><span class="emphasis"><em>Notes</em></span></p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>This encoding is obviously not as compact as it could be: in
particular, there are lots of redundant representations of
illegal positions where both players have checkers on the same
point. Theoretically, it would be possible to get it down to 64
bits by using <a class="ulink" href="http://www.bkgm.com/rgb/rgb.cgi?view+371" target="_top">Walter Trice's </a>
<a class="ulink" href="http://www.bkgm.com/rgb/rgb.cgi?view+371" target="_top"><span class="emphasis"><em>D() expressions</em></span></a>, but I think you'd have to be a mathematical masochist
to try it! </p></li><li class="listitem"><p>Thanks to Tom Keith and David desJardins for their
suggestions on simplifying the encoding without increasing the
worst case length. </p></li></ol></div></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="gnubg-tech_matchid"></a>A technical description of the Match ID</h3></div></div></div><p>This section describes how the match ID is calculated. The match
ID can be used for easy exchange of positions for gnubg users in
conjunction with the position ID. The match key is a 9 byte
representation of the match score, match length, value of cube, owner
of cube, Crawford game flag, player on roll, player to make a
decision, doubled flag, resigned flag, and the dice rolled. The match
ID is the 12 character Base64 encoding of the match key. Match key</p><p>The match key is a bit string of length 66:</p><div class="informaltable"><table border="1"><colgroup><col /><col /><col /><col /><col /><col /><col /><col /></colgroup><tbody><tr><td>1-4</td><td>5-6</td><td>7</td><td>8</td><td>9-11</td><td>12</td><td>13</td><td>14-15</td><td>16-18</td><td>19-21</td><td>22-36</td><td>37-51</td><td>52</td></tr><tr><td>Cube</td><td>CubeOwner</td><td>DiceOwner</td><td>Crawford</td><td>GameState</td><td>TurnOwner</td><td>Double</td><td>Resign</td><td>Dice1</td><td>Dice2</td><td>MatchLen x 15 </td><td>Score1 x 15</td><td>Score2 x 15</td></tr></tbody></table></div><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>Bit 1-4 contains the 2-logarithm of the cube value. For
example, a 8-cube is encoded as 0011 binary (or 3), since 2 to the
power of 3 is 8. The maximum value of the cube in with this
encoding is 2 to the power of 15, i.e., a 32768-cube. </p></li><li class="listitem"><p>Bit 5-6 contains the cube owner. 00 if player 0 owns the cube,
01 if player 1 owns the cube, or 11 for a centered cube. </p></li><li class="listitem"><p>Bit 7 is the player on roll or the player who did roll (0 and
1 for player 0 and 1, respectively). </p></li><li class="listitem"><p>Bit 8 is the Crawford flag: 1 if this game is the Crawford
game, 0 otherwise. </p></li><li class="listitem"><p>Bit 9-11 is the game state: 000 for no game started, 001 for
playing a game, 010 if the game is over, 011 if the game was
resigned, or 100 if the game was ended by dropping a cube. </p></li><li class="listitem"><p>Bit 12 indicates whose turn it is. For example, suppose player
0 is on roll then bit 7 above will be 0. Player 0 now decides to
double, this will make bit 12 equal to 1, since it is now player
1's turn to decide whether she takes or passes the cube. </p></li><li class="listitem"><p>Bit 13 indicates whether an doubled is being offered. 0 if no
double is being offered and 1 if a double is being offered.
</p></li><li class="listitem"><p>Bit 14-15 indicates whether an resignation was offered. 00 for
no resignation, 01 for resign of a single game, 10 for resign of a
gammon, or 11 for resign of a backgammon. The player offering the
resignation is the inverse of bit 12, e.g., if player 0 resigns a
gammon then bit 12 will be 1 (as it is now player 1 now has to
decide whether to accept or reject the resignation) and bit 13-14
will be 10 for resign of a gammon. </p></li><li class="listitem"><p>Bit 16-18 and bit 19-21 is the first and second die,
respectively. 0 if the dice has not yet be rolled, otherwise the
binary encoding of the dice, e.g., if 5-2 was rolled bit 16-21
will be 101-010. </p></li><li class="listitem"><p>Bit 22 to 36 is the match length. The maximum value for the
match length is 32767. A match length of zero indicates that the
game is a money game. </p></li><li class="listitem"><p>Bit 37-51 and bit 52-66 is the score for player 0 and player 1
respectively. The maximum value of the match score is 32767.
</p></li></ol></div><p>For example, assume the score is 2-4 in a 9 point match with
player 0 holding a 2-cube, and player 1 has just rolled 52. The match
key for this will be (note that the bit order is reversed below for
readability)</p><p>1000 00 1 0 100 1 0 00 101 010 100100000000000 010000000000000
001000000000000</p><p>In little endian the bytes looks like:</p><p>01000001 10001001 00101010 00000001 00100000 00000000 00100000
00000000 00</p><p>0x41 0x89 0x2A 0x01 0x20 0x00 0x20 0x00 0x00</p><p>Analogous to the position ID from the previous section the match
ID format is simply the Base64 encoding of the key.</p><p>To continue the example above, the 9 8-bit bytes are grouped into
12 6-bits groups:</p><p>010000 011000 100100 101010 000000 010010 000000 000000 001000
000000 000000 000000</p><p>In Base64 encoding, the groups are represented as:</p><p>Q Y k q A S A A I A A A</p><p>So, the match id is simply:</p><p>QYkqASAAIAAA</p><p>If someone post a match ID you can set up the position in gnubg by
writing or pasting it into the Match ID text input field on the main
window, or by executing the command</p><p>set matchid QYkqASAAIAAA.</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="gnubg-tech_css"></a>Description of the CSS style sheet</h3></div></div></div><p>As mentioned above <span class="application">GNU Backgammon</span>
writes a CSS style sheet along with the generated XHTML file. The CSS
style sheet may be written verbatim in the header section of the XHTML
file, to an external file named gnubg.css, or inside the tags using
the style attribute. If you wish to make any modifications to the
style sheet without modifying the actual source code of
<span class="application">GNU Backgammon</span> you have to choose one of
the first two methods. Note that the special export for Kit Woolsey's
GammOnLine uses the third method since the XHTML is pasted into a web
page without the possibility to modify the header section of the page
where the style sheet is defined. Thus, it's not possible to modify
the style of the generated XHTML for GammOnLine without modifications
of the source code or extensive search and replace in the generated
XHTML.</p><p>Below follows a description of the CSS classes used in the XHTML
export:</p><div class="informaltable"><table border="1"><colgroup><col /><col /></colgroup><tbody><tr><td>Class</td><td>Description</td></tr><tr><td>.movetable</td><td>Style applied to the entire table used for the move analysis</td></tr><tr><td>.moveheader</td><td>The header of the move analysis table</td></tr><tr><td>.movenumber</td><td>The rank number of a move in the move analysis</td></tr><tr><td>.moveply</td><td>The column indicating the number of plies or rollout</td></tr><tr><td>.movemove</td><td>The formatted move, e.g., 13/7 8/7.</td></tr><tr><td>.moveequity</td><td>The column with the equity or MWC.</td></tr><tr><td>.movethemove</td><td>Special style for row that contains the actual move chosen by the player</td></tr><tr><td>.moveodd</td><td>Special style for the odd rows. Can be used to give an alternating color for the rows.</td></tr><tr><td>.percent</td><td>Style for the game winning probabilities and equities in the move analysis.</td></tr><tr><td>.blunder</td><td>Emphasis blunders, e.g., <span class="emphasis"><em>Alert: missed double</em></span> or <span class="emphasis"><em>Alert: bad move</em></span>.</td></tr><tr><td>.joker</td><td>Emphasis very good or bad rolls, e.g., <span class="emphasis"><em>Alert: unlucky roll</em></span>.</td></tr><tr><td>.stattable</td><td>The style applied to the entire table with game, match, and session statistics</td></tr><tr><td>.stattableheader</td><td>The header row of the statistics table</td></tr><tr><td>.result</td><td>Style for the text indicating the outcome of the game or match, e.g., <span class="emphasis"><em>Jørn Thyssen wins 16 points</em></span>.</td></tr><tr><td>.tiny</td><td>Currently unused.</td></tr><tr><td>.cubedecision</td><td>The style applied to the entire cube decision table</td></tr><tr><td>.cubedecisionheader</td><td>Style for the header row of the cube decision table</td></tr><tr><td>.cubeequity</td><td>Style for any equity or MWC in the cube decision table</td></tr><tr><td>.cubeaction</td><td>Style for the text indicating the correct cube action</td></tr><tr><td>.cubeply</td><td>Style for the text that states the level of evaluation</td></tr><tr><td>.cubeprobs</td><td>Style for the game winning probabilities in the cube decision table</td></tr><tr><td>.comment</td><td>The style applied to the entire table used for annotations or comments, e.g., the kibitzing from imported SGG files</td></tr><tr><td>.commentheader</td><td>The style applied to the header row of the annotations' table</td></tr><tr><td>.number</td><td>Currently unused</td></tr><tr><td>.fontfamily</td><td>Style applied to the entire body of the XHTML document.</td></tr><tr><td>.block</td><td>Style applied to the images in the export to avoid gaps between individual pictures both horizontally and vertically.</td></tr><tr><td>.positionid</td><td>Style for the Position ID and match ID.</td></tr></tbody></table></div></div></div><div class="sect1"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="gnubg-faq"></a>Frequently Asked Questions</h2></div></div></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="gnubg-faq_general"></a>General questions</h3></div></div></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-faq_general_gnubg"></a>What is <span class="application">GNU Backgammon</span>?</h4></div></div></div><p><span class="application">GNU Backgammon</span> (gnubg) is a program for
playing and analysing backgammon positions, games and matches. It's
based on a neural network. You may play <span class="application">GNU
Backgammon</span> using the command line or a graphical
interface based on GTK+.</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-faq_general_os"></a>What operating systems are supported?</h4></div></div></div><p><span class="application">GNU Backgammon</span> is mostly developped
on <span class="emphasis"><em>GNU/Linux</em></span>. It also builds and runs under
other Unix operating systems like those derived from
<span class="emphasis"><em>BSD</em></span> or
<span class="emphasis"><em>Solaris</em></span>. The main prerequisite is the
availability of the GLib library at version 2.6 or later.
</p><p>Installable packages for
<span class="emphasis"><em>MS Windows</em></span> and <span class="emphasis"><em>Mac OS X</em></span> are
available for download at the project official website. Already
built packages are often provided by Linux distributions as well.
</p><p>When you successfully port
GNU Backgammon to other operating systems, you are welcome to give us
a note at <a class="ulink" href="mailto:bug-gnubg@gnu.org" target="_top">the GNU backgammon
mailing list.</a>
</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-faq_general_getit"></a>Where do I get it?</h4></div></div></div><p>The official website is <a class="ulink" href="http://www.gnubg.org/" target="_top">http://www.gnubg.org</a>. Binaries and source code for
<span class="application">GNU Backgammon</span> can be downloaded from
this site. Up to date source code can be accessed through <a class="ulink" href="https://savannah.gnu.org/cvs/?group=gnubg" target="_top">CVS</a>.</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-faq_general_pay"></a>What do I have to pay for <span class="application">GNU
Backgammon</span>?</h4></div></div></div><p><span class="application">GNU Backgammon</span> is <span class="emphasis"><em>Free
Software</em></span> and is a part of the <span class="emphasis"><em>GNU
Project</em></span>. You may download it for free. For more information
see the <a class="ulink" href="http://www.gnu.org/licenses/gpl.html" target="_top">GNU General
Public License</a>. But be aware that <span class="application">GNU
Backgammon</span> is not <span class="emphasis"><em>public domain
software</em></span> or <span class="emphasis"><em>shareware</em></span> as you perhaps
know from <span class="emphasis"><em>MS Windows</em></span>. <span class="application">GNU
Backgammon</span> is free as in <span class="emphasis"><em>freedom</em></span>,
i.e. all the source code is there for you to inspect, change or
distribute as long as you keep said license.</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-faq_general_gnu"></a>This GNU stuff sounds interesting</h4></div></div></div><p>Take a look at the <a class="ulink" href="http://www.gnu.org/" target="_top">GNU home
page</a>. It's also the page for Free Software Foundation.</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-faq_general_backgammon"></a>I want to learn more about backgammon</h4></div></div></div><p>A good place to start is <a class="ulink" href="http://www.bkgm.com/" target="_top">Backgammon Galore</a>. For an extensive link collection, go to
<a class="ulink" href="http://www.chicagopoint.com/links.html" target="_top">Gammon
Links.</a>
</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-faq_general_questions"></a>Though I really read all the documentation I still have
questions</h4></div></div></div><p>Send an email to <a class="ulink" href="mailto:bug-gnubg@gnu.org" target="_top">the GNU
backgammon mailing list.</a> If it is a bug, be sure to include
the name of your operating system, the version of gnubg you use, and
any error messages you receive. Try to describe exactly what happens
before the error occurs.</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-faq_general_ideas"></a>I want to make a few proposals, I have new ideas</h4></div></div></div><p>You're welcome! Send an email with your suggestions to <a class="ulink" href="mailto:bug-gnubg@gnu.org" target="_top">the GNU backgammon mailing
list.</a>
</p></div></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="gnubg-faq_install"></a>How to install</h3></div></div></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-faq_install_other"></a>Do I need some other software to run <span class="application">GNU
Backgammon</span>?</h4></div></div></div><p>No. Everything you need is included in the binaries.</p><p>If you want to use the 3D board version on Linux, you might have
to install the additional libraries that can be found as well on
<a class="ulink" href="http://www.gnubg.org/index.php?itemid=24" target="_top">this
page</a>. (acepoint's directory)</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-faq_install_new"></a>I want to install a newer version</h4></div></div></div><p>Go ahead, your settings should be saved.</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-faq_install_compile"></a>I would like to compile it from the source code</h4></div></div></div><p>Good luck to you! Download the source code and make sure to read
one of the two following two items.</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-faq_install_compilelinux"></a>What software do I need for compiling under GNU/Linux?</h4></div></div></div><p>Unpack the <span class="application">GNU Backgammon</span> snapshots and
follow the instructions of the file `INSTALL'. </p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-faq_install_compilems"></a>What software do I need for compiling under MS Windows?</h4></div></div></div><p>Follow the instructions at <a class="ulink" href="http://www.gnubg.org/index.php?itemid=50" target="_top">http://www.gnubg.org/index.php?itemid=50</a>.</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-faq_install_nocompile"></a>It does not compile</h4></div></div></div><p>Check that you have installed all necessary development packages.</p><p>Look for warnings or errors during compiling. If you still don't
have a clue, send a message to
<code class="email"><<a class="email" href="mailto:bug-gnubg@gnu.org">bug-gnubg@gnu.org</a>></code>.</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-faq_install_cpu"></a>On what CPU will <span class="application">GNU Backgammon</span> run
fastest?</h4></div></div></div><p><span class="application">GNU Backgammon</span>'s speed depends on the
CPU only. It doesn't need much memory (any machine not totally obsolete
will have enough) and does little or no I/O (a fast disk or a SSD won't make any difference).
</p><p>The table below lists CPUs and the result of the command <span class="guimenu">Analyse</span> → <span class="guimenuitem">Evaluation speed</span>, showing the relative speed of various processors.
Note that these numbers are not directly comparable with those given by the similar command from <span class="application">eXtreme Gammon</span>.
</p><div class="informaltable"><table border="1"><colgroup><col /><col /><col /><col /><col /><col /><col /></colgroup><tbody><tr><td>Evals/sec</td><td>CPU</td><td>System/Main board</td><td>RAM</td><td>OS </td><td>GNUBG-Version</td><td> </td></tr><tr><td>449500</td><td>Intel Core i5-2400 3.10 GHz</td><td>Dell Optiplex 790</td><td>4 GB</td><td>CentOS 6</td><td>1.02</td><td>4 threads</td></tr><tr><td>258600</td><td>Intel Core i5-2400 3.10 GHz</td><td>Dell Optiplex 790</td><td>4 GB</td><td>CentOS 6</td><td>1.02</td><td>2 threads</td></tr><tr><td>197700</td><td>Intel Core i5-3320M 2.60 GHz</td><td>Lenovo T430</td><td>4 GB</td><td>Win XP SP3</td><td>1.02</td><td>2 threads</td></tr><tr><td>131400</td><td>Intel Core i5-2400 3.10 GHz</td><td>Dell Optiplex 790</td><td>4 GB</td><td>CentOS 6</td><td>1.02</td><td>1 thread</td></tr><tr><td>125100</td><td>Intel Core 2 Duo P8400 2.26 GHz</td><td>Dell Latitude E6400</td><td>2 GB</td><td>Win XP SP3</td><td>1.02</td><td>2 threads</td></tr><tr><td>100100</td><td>Intel Core i5-3320M 2.60 GHz</td><td>Lenovo T430</td><td>4 GB</td><td>Win XP SP3</td><td>1.02</td><td>1 thread</td></tr><tr><td>64300</td><td>Intel Core 2 Duo T7500 2.2 GHz</td><td>Dell Latitude D630</td><td>4 GB</td><td>FreeBSD 9.2</td><td>1.02</td><td>1 thread</td></tr><tr><td>63500</td><td>Intel Core 2 Duo P8400 2.26 GHz</td><td>Dell Latitude E6400</td><td>2 GB</td><td>Win XP SP3</td><td>1.02</td><td>1 thread</td></tr><tr><td>37600</td><td>Intel Pentium 4 2.8 GHz</td><td>Dell Optiplex GX270</td><td>1 GB</td><td>CentOS 5</td><td>1.02</td><td class="auto-generated"> </td></tr><tr><td>28000</td><td>Intel Core Duo 1.66 GHz</td><td>Mac mini Core Duo</td><td>512 MB</td><td>Win XP SP2</td><td>0.14-mingw</td><td class="auto-generated"> </td></tr><tr><td>27000</td><td>Intel Pentium M 735 (1.7 GHz)</td><td>AOpen 1557-J</td><td>1024 MB</td><td>Win XP SP2</td><td>0.14-mingw</td><td class="auto-generated"> </td></tr><tr><td>26000</td><td>Intel Celeron 331 2.66 GHz</td><td>Dell Dimension 3100</td><td>512 MB</td><td>Win XP SP2</td><td>0.14.3-devel</td><td class="auto-generated"> </td></tr><tr><td>24500</td><td>AMD Sempron 2800+ (2000 MHz)</td><td>Asus K8V-X</td><td>768 MB</td><td>Win XP SP2</td><td>0.14.3-devel</td><td class="auto-generated"> </td></tr><tr><td>23000</td><td>Intel Pentium 4 2.8 GHz</td><td>Asus P4P800D</td><td>1024 MB</td><td>Win XP SP2</td><td>0.14.3-devel</td><td class="auto-generated"> </td></tr><tr><td>21759</td><td>AMD Athlon64 3000+ (32bit mode)</td><td>Acer Aspire 1522</td><td>512 MB</td><td>Kubuntu 5.04</td><td>0.14.3-devel</td><td class="auto-generated"> </td></tr><tr><td>20120</td><td>AMD Athlon XP 2500+ (1833 Mhz)</td><td>MSI K7N-Delta2</td><td>1024 MB</td><td>Suse Linux 9.2</td><td>0.14.3-devel</td><td class="auto-generated"> </td></tr><tr><td>19200</td><td>Intel Pentium M 1.6 GHz</td><td>IBM ThinkPad X41</td><td>1024 MB</td><td>Win XP SP2</td><td>0.14.3-devel</td><td class="auto-generated"> </td></tr><tr><td>14400</td><td>Intel Pentium III-M 1GHz</td><td>Sony Vaio PCG-R600HFPD</td><td>256 MB</td><td>Win XP SP2</td><td>0.16-mingw</td><td class="auto-generated"> </td></tr><tr><td>8520</td><td>Intel Celeron 750 MHz</td><td>Toshiba Satellite 4600</td><td>256 MB</td><td>Win XP SP1</td><td>1.02</td><td class="auto-generated"> </td></tr><tr><td>6990</td><td>Intel Celeron 600 MHz</td><td>Toshiba Satellite 4310</td><td>128 MB</td><td>Win XP SP2</td><td>1.02</td><td class="auto-generated"> </td></tr></tbody></table></div></div></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="gnubg-faq_start"></a>Running <span class="application">GNU Backgammon</span></h3></div></div></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-faq_start_error"></a>I get an error message when starting</h4></div></div></div><p>Well, your computer wants to communicate with you. Give it a
chance and read (and try to understand) what it is telling you. Then
read the next items carefully:</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-faq_start_missing"></a><span class="application">GNU Backgammon</span> complains about missing
files</h4></div></div></div><p><span class="application">GNU Backgammon</span> reads several different
files at start-up. It will first try to read a file called gnubg.wd.
This is a file which contains all the neural net weights and is
necessary for the program to evaluate positions. If this file is not
found, or found corrupted or with an incompatible version,
<span class="application">GNU Backgammon</span> will search for a weights
file called gnubg.weights. This file also contains the neural net
weights, but is stored in ASCII format. If none of these files are
found, <span class="application">GNU Backgammon</span> will start, but it
will give you a warning about these missing files, and it will play
<span class="emphasis"><em>very</em></span> poorly.</p><p><span class="application">GNU Backgammon</span> will also read the
bearoff databases at start-up. There are usually two bearoff
databases. The first is called gnubg_os0.bd, and has stored data about
the bearoff probabilities of all position where both players have 15
or fewer checkers left on their six home board points. If this file is
not found, <span class="application">GNU Backgammon</span> will create a
heuristic bearoff database for these positions. This database is a
also called the 'One Sided Database', since it evaluates each player
separately. The other bearoff database is called gnubg_ts0.bd. This
bearoff database contains win probabilities for all bearoff positions
with six or less checkers. It also contains cubeful equities (Money
Game) for all the positions. If this file is not found at start-up,
<span class="application">GNU Backgammon</span> will evaluate late bearoff
positions with the one sided bearoff database.</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-faq_start_beginner"></a>Starting from the WinXP menu it plays like a beginner</h4></div></div></div><p>Open the MS Windows menu and go to the entry for gnubg.
Right-click with the mouse and choose `properties'. Check, if the
`working path' is the same directory as the `*.exe'-file one line
above. If not, adjust the working path.</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-faq_start_screen"></a>My screen mixes up while starting <span class="application">GNU
Backgammon</span></h4></div></div></div><p>Install the newest driver for your graphic card. Be sure that you
have chosen at least a desktop resolution of 65535 (16 bit color
depth). If your card is a ATI Rage <span class="emphasis"><em>somewhat</em></span> there
still might be some problems with the graphical interface (GTK+) and
MS Windows.</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-faq_start_gtk"></a>I only get a command-line interface</h4></div></div></div><p>Using MS Windows, just click on the correct menu entry
(`<span class="application">GNU Backgammon</span> for windows'). If it
still doesn't work, check whether `c:\[path-to-your-gnubg]\gnubg.exe'
exists or not.</p><p>GNU/Linux users should check if <a class="ulink" href="http://www.gtk.org/" target="_top">GTK+</a> is installed.</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-faq_start_settings"></a>When I restart <span class="application">GNU Backgammon</span> all my
settings are gone</h4></div></div></div><p>Did you save your settings <span class="guimenu">Settings</span> → <span class="guimenuitem">Save settings</span> before you quit?</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-faq_start_cl"></a>I do not need this graphical stuff</h4></div></div></div><p>For <span class="emphasis"><em>GNU/Linux</em></span> users: open a terminal and run
<span class="command"><strong>gnubg -t</strong></span>.</p><p><span class="productname">MS Windows</span>™ users: Look for a file
called <span class="command"><strong>gnubg-cli.exe</strong></span> in <span class="application">GNU
Backgammon</span>'s install directory or open the MS Windows
menu <span class="guimenu">Start</span> → <span class="guimenuitem">Run...</span> and type
<span class="command"><strong>c:\[path-to-your-gnubg]\gnubg-cli.exe</strong></span>. There is
also a menu entry GNU Backgammon Command Line Interface.</p></div></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="gnubg-faq_play"></a>Playing backgammon</h3></div></div></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-faq_play_session"></a>What is the difference of a new game or match or session?</h4></div></div></div><p>When you start a new match, you will be asked to play to a certain
amount of points (for example, 7 points). The player who firstly
reaches this amount wins the match. Starting a new session means
playing to an infinite amount. Be aware that the rules do slightly
differ, mainly the Jacoby rule is applies to sessions and the Crawford
to match play.</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-faq_play_beaver"></a>What is a beaver in Backgammon?</h4></div></div></div><p>A beaver is only allowed in a money game session. To beaver means
to redouble, retaining control of the cube, immediately after your
opponent doubles. For more information see the <a class="ulink" href="http://www.bkgm.com/glossary.html#B" target="_top">glossary at Backgammon
Galore</a>.</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-faq_play_move"></a>How do I move the checkers?</h4></div></div></div><p>The easiest way to move checkers is to "<span class="emphasis"><em>drag and
drop</em></span>." Put your mouse pointer over a checker you want to
move, press the left mouse button and drag the checker to the desired
point, holding down the button while dragging.</p><p>If you prefer to use mouse clicks, the left mouse button is for
the left die shown on your board. Right click your mouse for the right
die.</p><p>If you always want the higher number displayed on the left, go to
the menu <span class="guimenu">Settings</span> → <span class="guimenuitem">Appearance</span> → <span class="guimenuitem"> General </span> and select Show higher die on left.</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-faq_play_5"></a>Why am I allowed to place more than 5 checkers on a point?</h4></div></div></div><p>The official backgammon tournament rules allow to put
up to all 15 checkers on a point. Playing with a maximum of 5
checkers, sometimes known as the Egyptian Rule, is no longer
supported by
<span class="application">GNU Backgammon</span>.</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-faq_play_poorly"></a><span class="application">GNU Backgammon</span> plays poorly</h4></div></div></div><p>Are you sure? If the answer is yes you should think about going to
Monte Carlo this summer and win the Backgammon World Championship. If
this plan fails, check whether the weights file is loaded at start-up.
See also <a class="xref" href="#gnubg-faq_start_missing" title="GNU Backgammon complains about missing files">the section called “<span class="application">GNU Backgammon</span> complains about missing
files”</a></p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-faq_play_strong"></a><span class="application">GNU Backgammon</span> is too strong for me</h4></div></div></div><p>Go to the menu <span class="guimenu">Settings</span> → <span class="guimenuitem">Players</span> and change the values for Player 0. There is also a set
of predefined settings you may choose from.</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-faq_play_cheat"></a>I think the bot is cheating</h4></div></div></div><p>In its default configuration, the dice generator does not cheat.
In the menu Settings you may choose between different random dice
generators. If you still think <span class="application">GNU
Backgammon</span> is cheating, program your own dice generator
or roll manually. It doesn't cheat!</p></div></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="gnubg-faq_settings"></a>Settings</h3></div></div></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-faq_settings_name"></a>Where can I change the name of the human player?</h4></div></div></div><p>Go to the menu <span class="guimenu">Settings</span> → <span class="guimenuitem"> Players....</span> and click on Player 1. At the top there is a field to
change the human player's name.</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-faq_settings_colors"></a>How do I change the colors?</h4></div></div></div><p>Go to the menu <span class="guimenu">Settings</span> → <span class="guimenuitem"> Appearance </span>. Here you may change the color of checkers, the points
and the board itself.</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-faq_settings_beeps"></a>How do I stop the annoying beeps?</h4></div></div></div><p>Go to the menu<span class="guimenu">Settings</span> → <span class="guimenuitem"> Appearance </span> and click on the `General' tab at the right. Disable the
option `Beep on illegal input'.</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-faq_settings_plies"></a>What are Plies?</h4></div></div></div><p>A ply describes how far <span class="application">GNU Backgammon</span>
evaluates the position. <span class="emphasis"><em>0-ply</em></span> means that
<span class="application">GNU Backgammon</span> estimates the worth of the
position as it is. A <span class="emphasis"><em>1-ply</em></span> evaluation looks one
step deeper, i.e. it evaluates the position after making the best
possible move for each of the 21 different rolls and returns the
averaged result. <span class="emphasis"><em>2-ply</em></span> is another roll further
and so on.</p><p>The more plies you choose, the more you strengthen
<span class="application">GNU Backgammon</span>. Keep in mind that this
will also decrease the playing speed.</p><p>Note also that <span class="emphasis"><em>0-ply</em></span> in <span class="application">GNU
Backgammon</span> is equivalent to the
<span class="emphasis"><em>1-ply</em></span> evaluation of Snowie.</p><p>It's possible that Snowie's is a <span class="emphasis"><em>playing</em></span> ply
while gnubg's is a <span class="emphasis"><em>position evaluation</em></span> ply. When
playing at 1-ply Snowie will make each possible move for the player's
roll (that's 1 ply) and analyse the resulting positions. Playing at
2-ply it will take each of those positions and make all the opponent
moves for all possible rolls (the 2nd ply) and then analyse the
resulting positions. In <span class="application">GNU Backgammon</span> the
initial set of possible moves is taken for granted, i.e. not counted
as a ply, because gnubg's plies are position evaluation plies. Thus,
for each of those possible moves a 0-ply analysis is done. gnubg's
discounting of the first set of moves perhaps makes the counting seem
funny.</p><p>Looking at it a different way, if you give <span class="application">GNU
Backgammon</span> a position and analyse it at 1-ply, it will
make all the moves for all possible rolls (the 1st ply) and then
analyse the resulting positions. With Snowie it will assume that the
position arose from a move (that's a pretend 1st ply) then make all
the moves for all possible rolls (the 2nd ply) and analyse them. This
time it's Snowie that seems to be counting strangely.</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-faq_settings_noise"></a>What is noise?</h4></div></div></div><p>Noise is a facility for disturbing <span class="application">GNU
Backgammon</span>'s 0-ply evaluation. Raising the noise level
decreases its playing strength.</p></div></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="gnubg-faq_analysing"></a>Analysing</h3></div></div></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-faq_analysing_id"></a>What are these funny letters at the right bottom?</h4></div></div></div><p>You will find a small window titled `GNUbg ID'
at the bottom of the <span class="application">GNU Backgammon</span> window.
It contains an short, textual, representation of the position at hand,
suitable for easily copying and pasting positions.</p><p>It is composed of a `Position ID' describing the checkers position and a `Match ID' for the other features (match score, cube position and value, dice, who is on roll...).
A detailed description of both formats is found earlier in <a class="xref" href="#gnubg-tech_postionid" title="A technical description of the Position ID">the section called “A technical description of the Position ID”</a>.</p><p>Pasting a `XGID' (a similar shortcut used by <span class="application">eXtreme Gammon</span>) there is recognized as well.</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-faq_analysing_edit"></a>How do I set up a position manually?</h4></div></div></div><p>Open a new game, match or session. If gnubg already rolls the
dice, don't bother. Press `edit', and either type the position_id and
press Enter on your keyboard, or use the mouse to set up the checkers.</p><p>A mouse click at the border of the board empties the point. A left
or right click sets up a certain amount of checkers depending on where
exactly on the pip you click. Set up the cube with a right mouse click
on it.</p><p>You can also drag and drop checkers when holding down the Ctrl
key.</p><p>Finally, go to the menu and select `Game, Set turn' to choose the
player on roll. The dice will then disappear.</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-faq_analysing_import"></a>Which formats can I use to import matches and positions?</h4></div></div></div><p>Import of matches and positions from a number of file formats is
possible: (.gam) GammonEmpire Game,
(.gam) PartyGammon Game, (.mat) Jellyfish Match, (.pos) Jellyfish
Position, (.sgf) Gnu Backgammon File, (.sgg) GamesGrid Save Game,
(.tmg) TrueMoneyGames, (.txt) Snowie Text</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-faq_analysing_sides"></a>How can I switch the players sides?</h4></div></div></div><p>Go to the menu `Game' and click on `Swap players'.</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-faq_analysing_error"></a>What do <span class="emphasis"><em>!</em></span> and <span class="emphasis"><em>?</em></span> mean?</h4></div></div></div><p>After analysing a game or a match <span class="application">GNU
Backgammon</span> is able to do some comments on checker play
or cube decisions. Open the menu `Window, Game record' and you will
see a list of the moves. If the actual move or cube decision differs
from the best, <span class="application">GNU Backgammon</span> will put a
comment on it.</p><p>The default settings are:</p><div class="informaltable"><table border="1"><colgroup><col class="c1" /><col class="c2" /><col class="c3" /></colgroup><tbody><tr><td>-0.040</td><td>(doubtful):</td><td>?!</td></tr><tr><td>-0.080</td><td>(bad):</td><td>?</td></tr><tr><td>-0.160</td><td>(very bad):</td><td>??</td></tr></tbody></table></div><p>You may change these comment in the menu `Window, Annotation'
choosing another comment for moves and/or double</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-faq_analysing_rate"></a>How is the error rate determined?</h4></div></div></div><p><span class="application">GNU Backgammon</span> determines a player's
strength according to its average error (per move):</p><div class="informaltable"><table border="1"><colgroup><col class="c1" /><col class="c2" /></colgroup><tbody><tr><td>Average Error</td><td>Skill Level</td></tr><tr><td>0.000 .. 0.005</td><td>Extra-terrestrial</td></tr><tr><td>0.005 .. 0.010</td><td>World class</td></tr><tr><td>0.010 .. 0.015</td><td>Expert</td></tr><tr><td>0.015 .. 0.020</td><td>Advanced</td></tr><tr><td>0.020 .. 0.025</td><td>Intermediate</td></tr><tr><td>0.025 .. 0.030</td><td>Beginner</td></tr><tr><td>0.030 ..</td><td>Novice</td></tr></tbody></table></div><p>After analysing a game, match or session you can see the summary
in the menu `Analyse, ... statistics'. Note that you can't change the
ranges of these values.</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-faq_analysing_pips"></a>What does Pips mean?</h4></div></div></div><p>The pip count is a measurement showing the total number of pips
required for a player to bear off all checkers from the current
position. It can be regarded as a rough estimate of the
<span class="emphasis"><em>raceness</em></span> of the position. A player with a
lower pip count may in many situations want to try to race, whilst the
opponent (with the higher pip count) may want to try blocking/holding.
See also the <a class="ulink" href="http://www.bkgm.com/gloss/lookup.cgi?pip+count" target="_top">explanation on
BackGammon Galore</a>.</p><p>(For the non-english speaking community it might be helpful to
know that when you roll a six and a five, the total pips of that roll
is eleven.)</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-faq_analysing_epc"></a>What does EPC mean?</h4></div></div></div><p>When bearing off checkers, you may notice a display showing the
current <span class="emphasis"><em>EPC</em></span> value (next to the display of
<span class="emphasis"><em>Pips</em></span>). The EPC display can be turned on or off
under menu <span class="emphasis"><em>Settings -> Options ->
Display</em></span>.</p><p><span class="emphasis"><em>EPC</em></span> stands for Effective Pip Count, and is an
alternative measurement of the <span class="emphasis"><em>goodness</em></span> of the
position. The usual pip count can be a misleading
<span class="emphasis"><em>goodness</em></span> estimate when both players are bearing
off. What is more important (for making cubing decisions) is
<span class="emphasis"><em>the expected number of rolls</em></span> each player needs
to bear off hes checkers.</p><p>The effective pip count is defined as this expected number of
remaining rolls, multiplied with the average number of pips in a roll,
which is 8.167. (The average number of pips in a roll would be 7 if
rolling a double wouldn't yield a double pip count. A double-6
yields 24 pips, not 12.)</p><p>Thus, EPC takes into account not only the current pip count, but
also the expected pip wastage:</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>Effective Pip Count (EPC) = pip count + expected pip wastage
</p></li></ol></div><p>An example:</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>Position: 5 checkers on the 1-point, 4 checkers on the
2-point. </p></li><li class="listitem"><p>Pip count: 5x1 + 4x2 = 13 </p></li><li class="listitem"><p>EPC: 2.189 (expected number of remaining rolls) * 8.167 =
17.878 </p></li><li class="listitem"><p>Wasted: 17.878 - 13 = 4.878 </p></li></ol></div><p>It's clear (hopefully) that the expected pip wastage (and hence
the <span class="emphasis"><em>EPC</em></span>) increases with more checkers on lower
points (e.g. you get pip wastage when rolling a 6 to bear off a
checker from the 2- or 1-point).</p><p>It is further <a class="ulink" href="http://www.bkgm.com/gloss/lookup.cgi?effective+pip+count" target="_top">explained on BackGammon Galore</a>, especially in a <a class="ulink" href="http://www.bkgm.com/rgb/rgb.cgi?view+1076" target="_top">post by Douglas
Zare</a>.</p><p>How do one calculate the EPC then, or the expected number of
remaining rolls? GnuBG uses the one-sided bearoff database, which
contains the chance of bearing off the final checker in any given
number of rolls. A player would probably use some quite complicated
heuristics (please see the aforementioned post by Douglas Zare,
<span class="emphasis"><em>and do get back here and explain it!</em></span>)</p></div></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="gnubg-faq_abbr"></a>Abbreviations</h3></div></div></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-faq_abbr_gwc"></a>GWC?</h4></div></div></div><p><span class="emphasis"><em>GWC</em></span> is an abbreviation for game winning
chances.</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-faq_abbr_mwc"></a>MWC?</h4></div></div></div><p><span class="emphasis"><em>MWC</em></span> is an abbreviation for match winning
chances.</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-faq_abbr_dp"></a>DP?</h4></div></div></div><p>In the menu `Analyse, Game/Match/Session statistics' you will see
a window with some statistics. Near the bottom, you'll see four lines
beginning with `Missed ... and Wrong ...'. <span class="emphasis"><em>dp</em></span>
means <span class="emphasis"><em>doubling point</em></span> and describes a situation in
the game, where you probably should have doubled your opponent.</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-faq_abbr_cp"></a>CP?</h4></div></div></div><p>Cash-point(CP) is
your opponent's take-point now seen from your side of the
board (your cash-point which equals 100% minus your opponent's
take-point). <span class="application">GNU Backgammon</span>
uses the term <span class="emphasis"><em>missed double below cash-point</em></span>,
which means that the player should have doubled, and had he done so,
his opponent should take. <span class="emphasis"><em>Missed double above CP</em></span>
in a similar way means that the correct cube-action was double pass.</p><p>If you are the leader in the match, the relevant take- and
double-points will often look something like this (where TP*=CP):</p><div class="figure"><a id="gnubg-fig_doubleline"></a><p class="title"><strong>Figure 32. The double line</strong></p><div class="figure-contents"><div class="mediaobject"><img src="images/doubleline.png" alt="[[doubleline.png]]" /></div></div></div><br class="figure-break" /><p>The double windows (intervals) are:</p><p>[DP;CP] = Your double window! This window does not contain any
information about redoubles but only the distance to the point where
you do not want to play for the double amount of points.</p><p>[TP;DP] = 100% minus your opponent's double window now.</p><p>[reTP;reDP] = 100% minus your opponent's double window after he
has taken.</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-faq_abbr_tg"></a>TG?</h4></div></div></div><p><span class="emphasis"><em>TG</em></span> is an abbreviation for <span class="emphasis"><em>too
good</em></span> (to double). It points to a situation in the game,
where you probably should have kept the cube (mostly because of
decent, sometimes very good, gammon chances) rather than double out
your opponent.</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="gnubg-faq_abbr_epc"></a>EPC?</h4></div></div></div><p>See <a class="xref" href="#gnubg-faq_analysing_epc" title="What does EPC mean?">the section called “What does EPC mean?”</a>
</p><p>
<span class="emphasis"><em>This should be an internal link, not an external one. But I
can't figure out how to link internally to a subsection.
Anyone?</em></span>
</p></div></div></div><div xml:lang="en" class="appendix" lang="en"><div class="titlepage"><div><div><h2 class="title"><a id="legal"></a>A. GNU Free Documentation License</h2></div></div></div><p>Version 1.3, 3 November 2008</p><p>
Copyright © 2000, 2001, 2002, 2007, 2008
<a class="ulink" href="http://www.fsf.org/" target="_top">Free Software Foundation, Inc.</a>
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Everyone is permitted to copy and distribute verbatim copies of this
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</p><h3><a id="section0"></a>
0. PREAMBLE
</h3><p>
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</p><h3><a id="section2"></a>
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</p><h3><a id="section4"></a>
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</p><h3><a id="section5"></a>
5. COMBINING DOCUMENTS
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</p><h3><a id="section6"></a>
6. COLLECTIONS OF DOCUMENTS
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</p><h3><a id="section7"></a>
7. AGGREGATION WITH INDEPENDENT WORKS
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8. TRANSLATION
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</p><h3><a id="section9"></a>
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</p><h3><a id="section10"></a>
10. FUTURE REVISIONS OF THIS LICENSE
</h3><p>
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11. RELICENSING
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</p><h3><a id="addendum"></a>
ADDENDUM: How to use this License for your documents
</h3><p>
To use this License in a document you have written, include a copy of the
License in the document and put the following copyright and license
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</p><pre class="screen">Copyright © YEAR YOUR NAME
Permission is granted to copy, distribute and/or modify this document under the
terms of the GNU Free Documentation License, Version 1.3 or any later version
published by the Free Software Foundation; with no Invariant Sections, no
Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in
the section entitled “GNU Free Documentation License”.</pre><p>
If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts,
replace the “with… Texts.” line with this:
</p><pre class="screen">with the Invariant Sections being LIST THEIR TITLES, with the Front-Cover Texts
being LIST, and with the Back-Cover Texts being LIST.</pre><p>
If you have Invariant Sections without Cover Texts, or some other
combination of the three, merge those two alternatives to suit the
situation.
</p><p>
If your document contains nontrivial examples of program code, we
recommend releasing these examples in parallel under your choice of free
software license, such as the GNU General Public License, to permit their
use in free software.
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