/usr/lib/swi-prolog/doc/Manual/threads.html

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">

<html>
<head>
<title>SWI-Prolog 7.3.6 Reference Manual</title><link rel="home" href="index.html">
<link rel="contents" href="Contents.html">
<link rel="index" href="DocIndex.html">
<link rel="summary" href="summary.html">
<link rel="previous" href="errors.html">
<link rel="next" href="threadcreate.html">

<style type="text/css">

/* Style sheet for SWI-Prolog latex2html
*/

dd.defbody
{ margin-bottom: 1em;
}

dt.pubdef, dt.multidef
{ color: #fff;
padding: 2px 10px 0px 10px;
margin-bottom: 5px;
font-size: 18px;
vertical-align: middle;
overflow: hidden;
}

dt.pubdef { background-color: #0c3d6e; }
dt.multidef { background-color: #ef9439; }

.bib dd
{ margin-bottom: 1em;
}

.bib dt
{ float: left;
margin-right: 1.3ex;
}

pre.code
{ margin-left: 1.5em;
margin-right: 1.5em;
border: 1px dotted;
padding-top: 5px;
padding-left: 5px;
padding-bottom: 5px;
background-color: #f8f8f8;
}

div.navigate
{ text-align: center;
background-color: #f0f0f0;
border: 1px dotted;
padding: 5px;
}

div.title
{ text-align: center;
padding-bottom: 1em;
font-size: 200%;
font-weight: bold;
}

div.author
{ text-align: center;
font-style: italic;
}

div.abstract
{ margin-top: 2em;
background-color: #f0f0f0;
border: 1px dotted;
padding: 5px;
margin-left: 10%; margin-right:10%;
}

div.abstract-title
{ text-align: center;
padding: 5px;
font-size: 120%;
font-weight: bold;
}

div.toc-h1
{ font-size: 200%;
font-weight: bold;
}

div.toc-h2
{ font-size: 120%;
font-weight: bold;
margin-left: 2em;
}

div.toc-h3
{ font-size: 100%;
font-weight: bold;
margin-left: 4em;
}

div.toc-h4
{ font-size: 100%;
margin-left: 6em;
}

span.sec-nr
{
}

span.sec-title
{
}

span.pred-ext
{ font-weight: bold;
}

span.pred-tag
{ float: right;
padding-top: 0.2em;
font-size: 80%;
font-style: italic;
color: #fff;
}

div.caption
{ width: 80%;
margin: auto;
text-align:center;
}

/* Footnotes */
.fn {
color: red;
font-size: 70%;
}

.fn-text, .fnp {
position: absolute;
top: auto;
left: 10%;
border: 1px solid #000;
box-shadow: 5px 5px 5px #888;
display: none;
background: #fff;
color: #000;
margin-top: 25px;
padding: 8px 12px;
font-size: larger;
}

sup:hover span.fn-text
{ display: block;
}

/* Lists */

dl.latex
{ margin-top: 1ex;
margin-bottom: 0.5ex;
}

dl.latex dl.latex dd.defbody
{ margin-bottom: 0.5ex;
}

/* PlDoc Tags */

dl.tags
{ font-size: 90%;
margin-left: 5ex;
margin-top: 1ex;
margin-bottom: 0.5ex;
}

dl.tags dt
{ margin-left: 0pt;
font-weight: bold;
}

dl.tags dd
{ margin-left: 3ex;
}

td.param
{ font-style: italic;
font-weight: bold;
}

/* Index */

dt.index-sep
{ font-weight: bold;
font-size: +1;
margin-top: 1ex;
}

/* Tables */

table.center
{ margin: auto;
}

table.latex
{ border-collapse:collapse;
}

table.latex tr
{ vertical-align: text-top;
}

table.latex td,th
{ padding: 2px 1em;
}

table.latex tr.hline td,th
{ border-top: 1px solid black;
}

table.frame-box
{ border: 2px solid black;
}

</style>
</head>
<body style="background:white">
<div class="navigate"><a class="nav" href="index.html"><img src="home.gif" alt="Home"></a>
<a class="nav" href="Contents.html"><img src="index.gif" alt="Contents"></a>
<a class="nav" href="DocIndex.html"><img src="yellow_pages.gif" alt="Index"></a>
<a class="nav" href="summary.html"><img src="info.gif" alt="Summary"></a>
<a class="nav" href="errors.html"><img src="prev.gif" alt="Previous"></a>
<a class="nav" href="threadcreate.html"><img src="next.gif" alt="Next"></a>
</div>
<h1 id="sec:threads"><a id="sec:9"><span class="sec-nr">9</span> <span class="sec-title">Multithreaded 
applications</span></a></h1>

<a id="sec:threads"></a>

<p>SWI-Prolog multithreading is based on standard C language 
multithreading support. It is not like <em>ParLog</em> or other parallel 
implementations of the Prolog language. Prolog threads have their own 
stacks and only share the Prolog <em>heap</em>: predicates, records, 
flags and other global non-backtrackable data. SWI-Prolog thread support 
is designed with the following goals in mind.

<p>
<ul class="latex">
<li><i>Multithreaded server applications</i><br>
Today's computing services often focus on (internet) server 
applications. Such applications often have need for communication 
between services and/or fast non-blocking service to multiple concurrent 
clients. The shared heap provides fast communication, and thread 
creation is relatively cheap.<sup class="fn">140<span class="fn-text">On 
an Intel i7-2600K, running Ubuntu Linux 12.04, SWI-Prolog 6.2 creates 
and joins 32,000 threads per second elapsed time.</span></sup>

<p>
<li><i>Interactive applications</i><br>
Interactive applications often need to perform extensive computation. If 
such computations are executed in a new thread, the main thread can 
process events and allow the user to cancel the ongoing computation. 
User interfaces can also use multiple threads, each thread dealing with 
input from a distinct group of windows. See also <a class="sec" href="mt-xpce.html">section 
9.7</a>.

<p>
<li><i>Natural integration with foreign code</i><br>
Each Prolog thread runs in a native thread of the operating system, 
automatically making them cooperate with <em>MT-safe</em> foreign code. 
In addition, any foreign thread can create its own Prolog engine for 
dealing with calling Prolog from C code.
</ul>

<p>SWI-Prolog multithreading is based on the POSIX thread standard
<cite><a class="cite" href="Bibliography.html#Butenhof:1997:PPT">Butenhof, 
1997</a></cite> used on most popular systems except for MS-Windows. On 
Windows it uses the
<a class="url" href="http://sources.redhat.com/pthreads-win32/">pthread-win32</a> 
emulation of POSIX threads mixed with the Windows native API for 
smoother and faster operation. The SWI-Prolog thread implementation has 
been discussed in the ISO WG17 working group and is largely addopted by 
YAP and XSB Prolog.<sup class="fn">141<span class="fn-text">The latest 
version of the ISO draft can be found at <a class="url" href="http://logtalk.org/plstd/threads.pdf">http://logtalk.org/plstd/threads.pdf</a>. 
It appears to have dropped from the ISO WG17 agenda.</span></sup>

<p>
<hr>
<div style="text-align:center">

<h2>Section Index</h2>

</div>
<hr>
<div class="toc">
<div class="toc-h2"><a class="sec" href="threadcreate.html"><span class="sec-nr">9.1</span> <span class="sec-title">Creating 
and destroying Prolog threads</span></a></div>
<div class="toc-h2"><a class="sec" href="thmonitor.html"><span class="sec-nr">9.2</span> <span class="sec-title">Monitoring 
threads</span></a></div>
<div class="toc-h2"><a class="sec" href="threadcom.html"><span class="sec-nr">9.3</span> <span class="sec-title">Thread 
communication</span></a></div>
<div class="toc-h3"><a class="sec" href="threadcom.html#sec:9.3.1"><span class="sec-nr">9.3.1</span> <span class="sec-title">Message 
queues</span></a></div>
<div class="toc-h3"><a class="sec" href="threadcom.html#sec:9.3.2"><span class="sec-nr">9.3.2</span> <span class="sec-title">Signalling 
threads</span></a></div>
<div class="toc-h3"><a class="sec" href="threadcom.html#sec:9.3.3"><span class="sec-nr">9.3.3</span> <span class="sec-title">Threads 
and dynamic predicates</span></a></div>
<div class="toc-h2"><a class="sec" href="threadsync.html"><span class="sec-nr">9.4</span> <span class="sec-title">Thread 
synchronisation</span></a></div>
<div class="toc-h2"><a class="sec" href="thutil.html"><span class="sec-nr">9.5</span> <span class="sec-title">Thread 
support library(threadutil)</span></a></div>
<div class="toc-h3"><a class="sec" href="thutil.html#sec:9.5.1"><span class="sec-nr">9.5.1</span> <span class="sec-title">Debugging 
threads</span></a></div>
<div class="toc-h3"><a class="sec" href="thutil.html#sec:9.5.2"><span class="sec-nr">9.5.2</span> <span class="sec-title">Profiling 
threads</span></a></div>
<div class="toc-h2"><a class="sec" href="foreignthread.html"><span class="sec-nr">9.6</span> <span class="sec-title">Multithreaded 
mixed C and Prolog applications</span></a></div>
<div class="toc-h3"><a class="sec" href="foreignthread.html#sec:9.6.1"><span class="sec-nr">9.6.1</span> <span class="sec-title">A 
Prolog thread for each native thread (one-to-one)</span></a></div>
<div class="toc-h3"><a class="sec" href="foreignthread.html#sec:9.6.2"><span class="sec-nr">9.6.2</span> <span class="sec-title">Pooling 
Prolog engines (many-to-many)</span></a></div>
<div class="toc-h2"><a class="sec" href="mt-xpce.html"><span class="sec-nr">9.7</span> <span class="sec-title">Multithreading 
and the XPCE graphics system</span></a></div>
</div>
</body></html>
swi-prolog-nox 7.2.3-2 / usr / lib / swi-prolog / doc / Manual / threads.html
