/usr/share/octave/packages/linear-algebra-2.2.0/@blksparse/blksparse.m is in octave-linear-algebra 2.2.0-1build1.
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##
## This program is free software; you can redistribute it and/or modify
## it under the terms of the GNU General Public License as published by
## the Free Software Foundation; either version 3 of the License, or
## (at your option) any later version.
##
## This program is distributed in the hope that it will be useful,
## but WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
## GNU General Public License for more details.
##
## You should have received a copy of the GNU General Public License
## along with Octave; see the file COPYING. If not, see
## <http://www.gnu.org/licenses/>.
## -*- texinfo -*-
## @deftypefn{Function File} {@var{s} =} blksparse (@var{i}, @var{j}, @var{sv})
## @deftypefnx{Function File} {@var{s} =} blksparse (@var{i}, @var{j}, @var{sv}, @var{m}, @var{n})
## @deftypefnx{Function File} {@var{s} =} blksparse (@dots{}, @var{mode})
##
## Construct a block sparse matrix. The meaning of arguments is analogous to the
## built-in @code{sparse} function, except that @var{i}, @var{j} are indices of
## blocks rather than elements, and @var{sv} is a 3-dimensional array, the first two
## dimensions determining the block size. Optionally, @var{m} and @var{n} can be
## specified as the true block dimensions; if not, the maximum values of @var{i}, @var{j}
## are taken instead. The resulting sparse matrix has the size
##
## @example
## [@var{m}*@var{p}, @var{n}*@var{q}]
## @end example
##
## where
##
## @example
## @var{p} = size (@var{sv}, 1)
## @var{q} = size (@var{sv}, 2)
## @end example
##
## The blocks are located so that
##
## @example
## @var{s}(@var{i}(k):@var{i}(k)+@var{p}-1, @var{j}(k):@var{j}(K)+@var{q}-1) = @var{sv}(:,:,k)
## @end example
##
## Multiple blocks corresponding to the same pair of indices are summed, unless
## @var{mode} is "unique", in which case the last of them is used.
## @end deftypefn
function s = blksparse (i, j, sv, m = 0, n = 0, mode)
persistent chkver = check_version ();
if (nargin == 0)
i = j = zeros (0, 1);
sv = zeros (1, 1, 0);
s = class (struct ("i", i, "j", j, "sv", sv, "siz", [0, 0], "bsiz", [1, 1]), "blksparse");
return
endif
if (nargin < 3 || nargin > 6)
print_usage ();
endif
if (! isvector (i) || ! isvector (j))
error ("blksparse: i, j must be vectors");
elseif (ndims (sv) != 3)
error ("blksparse: sv must be a 3D array");
endif
if (nargin == 4 && ischar (m))
mode = m;
m = 0;
elseif (nargin < 6)
mode = "sum";
endif
if (strcmp (mode, "unique"))
summation = false;
elseif (strcmp (mode, "sum") || strcmp (mode, "summation"))
summation = true;
else
error ("blksparse: invalid mode: %s", mode);
endif
if (m == 0)
m = max (i);
endif
if (n == 0)
n = max (j);
endif
siz = [m, n];
ji = [j(:), i(:)];
[ji, fidx, ridx] = unique (ji, "rows");
j = ji(:,1);
i = ji(:,2);
if (summation)
sv = accumdim (ridx, sv, 3, rows (ji));
else
sv = sv(:,:,fidx);
endif
s = struct ("i", i, "j", j, "sv", sv, "siz", siz, "bsiz", size (sv)(1:2));
s = class (s, "blksparse");
endfunction
function ok = check_version ()
ok = compare_versions (version, "3.3.51", ">=");
if (! ok)
error ("blksparse: can only be used with Octave 3.3.51+");
endif
endfunction
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