--- /dev/null
+## Copyright (C) 2010 VZLU Prague
+##
+## 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} mtimes (@var{x}, @var{y})
+## Multiplies a block sparse matrix with a full matrix, or two block sparse
+## matrices. Multiplication of block sparse * sparse is not implemented.
+## If one of arguments is a scalar, it's a scalar multiply.
+## @end deftypefn
+
+function c = mtimes (a, b)
+ if (isa (a, "blksparse"))
+ if (isa (b, "blksparse"))
+ c = mtimes_ss (a, b);
+ else
+ c = mtimes_sm (a, b);
+ endif
+ elseif (isa (b, "blksparse"))
+ c = mtimes_ms (a, b);
+ else
+ error ("blksparse: invalid arguments to mtimes");
+ endif
+endfunction
+
+function y = mtimes_sm (s, x)
+ if (isscalar (x))
+ y = s;
+ y.sv *= x;
+ return;
+ elseif (issparse (x))
+ error ("blksparse * sparse not implemented.");
+ endif
+ siz = s.siz;
+ bsiz = s.bsiz;
+ ## Check sizes.
+ [xr, xc] = size (x);
+ if (xr != siz(2)*bsiz(2))
+ gripe_nonconformant (siz.*bsiz, [xr, xc]);
+ endif
+ ## Form blocks.
+ x = reshape (x, bsiz(2), siz(2), xc);
+ x = permute (x, [1, 3, 2]);
+ ## Scatter.
+ xs = x(:,:,s.j);
+ ## Multiply.
+ ys = blkmm (s.sv, xs);
+ ## Gather.
+ y = accumdim (s.i, ys, 3, siz(1));
+ y = permute (y, [1, 3, 2]);
+ ## Narrow blocks.
+ y = reshape (y, bsiz(1)*siz(1), xc);
+endfunction
+
+function y = mtimes_ms (x, s)
+ if (isscalar (x))
+ y = s;
+ y.sv *= x;
+ return;
+ elseif (issparse (x))
+ error ("sparse * blksparse not implemented.");
+ endif
+ siz = s.siz;
+ bsiz = s.bsiz;
+ ## Check sizes.
+ [xr, xc] = size (x);
+ if (xc != siz(1)*bsiz(1))
+ gripe_nonconformant ([xr, xc], siz.*bsiz);
+ endif
+ ## Form blocks.
+ x = reshape (x, xr, bsiz(2), siz(2));
+ ## Scatter.
+ xs = x(:,:,s.i);
+ ## Multiply.
+ ys = blkmm (xs, s.sv);
+ ## Gather.
+ y = accumdim (s.j, ys, 3, siz(2));
+ ## Narrow blocks.
+ y = reshape (y, xr, bsiz(2)*siz(2));
+endfunction
+
+function s = mtimes_ss (s1, s2)
+
+ ## Conformance check.
+ siz1 = s1.siz;
+ bsiz1 = s1.bsiz;
+ siz2 = s2.siz;
+ bsiz2 = s2.bsiz;
+ if (bsiz1(2) != bsiz2(1))
+ gripe_nonconformant (bsiz1, bsiz2, "block sizes");
+ elseif (siz1(2) != siz2(1))
+ gripe_nonconformant (bsiz1.*siz1, bsiz2.*siz2);
+ endif
+
+ ## Hardcore hacks, man!
+ ss = sparse (s1.i, s1.j, 1:length (s1.i), "unique");
+ ss = ss(:,s2.i);
+ [i, j, k] = find (ss);
+ sv = blkmm (s1.sv(:,:,k), s2.sv(:,:,j));
+ j = s2.j(j);
+
+ s = blksparse (i, j, sv, siz1(1), siz2(2));
+
+endfunction
+
+function gripe_nonconformant (s1, s2, what = "arguments")
+ error ("Octave:nonconformant-args", ...
+ "nonconformant %s (op1 is %dx%d, op2 is %dx%d)", what, s1, s2);
+endfunction