/usr/share/octave/packages/linear-algebra-2.2.0/@kronprod/mtimes.m is in octave-linear-algebra 2.2.0-1build1.
This file is owned by root:root, with mode 0o644.
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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, 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 this file. If not, see <http://www.gnu.org/licenses/>.
## -*- texinfo -*-
## @deftypefn {Function File} mtimes (@var{KP})
## XXX: Write documentation
## @end deftypefn
function retval = mtimes (M1, M2)
## Check input
if (nargin == 0)
print_usage ();
elseif (nargin == 1)
## This seems to be what happens for full and sparse matrices, so we copy this behaviour
retval = M1;
return;
endif
if (!ismatrix (M1) || !ismatrix (M2))
error ("mtimes: input arguments must be matrices");
endif
if (columns (M1) != rows (M2))
error ("mtimes: nonconformant arguments (op1 is %dx%d, op2 is %dx%d)",
rows (M1), columns (M1), rows (M2), columns (M2));
endif
## Take action depending on input types
M1_is_KP = isa (M1, "kronprod");
M2_is_KP = isa (M2, "kronprod");
if (M1_is_KP && M2_is_KP) # Product of Kronecker Products
## Check if the size match such that the result is a Kronecker Product
if (columns (M1.A) == rows (M2.A) && columns (M1.B) == rows (M2.B))
retval = kronprod (M1.A * M2.A, M1.B * M2.B);
else
## Form the full matrix of the smallest matrix and use that to compute the
## final product
## XXX: Can we do something smarter here?
numel1 = numel (M1);
numel2 = numel (M2);
if (numel1 < numel2)
retval = full (M1) * M2;
else
retval = M1 * full (M2);
endif
endif
elseif (M1_is_KP && isscalar (M2)) # Product of Kronecker Product and scalar
if (numel (M1.A) < numel (M1.B))
retval = kronprod (M2 * M1.A, M1.B);
else
retval = kronprod (M1.A, M2 * M1.B);
endif
elseif (M1_is_KP && ismatrix (M2)) # Product of Kronecker Product and Matrix
retval = zeros (rows (M1), columns (M2));
for n = 1:columns (M2)
M = reshape (M2 (:, n), [columns(M1.B), columns(M1.A)]);
retval (:, n) = vec (M1.B * M * M1.A');
endfor
elseif (isscalar (M1) && M2_is_KP) # Product of scalar and Kronecker Product
if (numel (M2.A) < numel (M2.B))
retval = kronprod (M1 * M2.A, M2.B);
else
retval = kronprod (M2.A, M1 * M2.B);
endif
elseif (ismatrix (M1) && M2_is_KP) # Product of Matrix and Kronecker Product
retval = zeros (rows (M1), columns (M2));
for n = 1:rows (M1)
M = reshape (M1 (n, :), [rows(M2.B), rows(M2.A)]);
retval (n, :) = vec (M2.B' * M * M2.A);
endfor
else
error ("mtimes: internal error for 'kronprod'");
endif
endfunction
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