Add a useful package (from Source forge) for octave

[CreaPhase.git] / octave_packages / linear-algebra-2.2.0 / @kronprod / times.m

diff --git a/octave_packages/linear-algebra-2.2.0/@kronprod/times.m b/octave_packages/linear-algebra-2.2.0/@kronprod/times.m
new file mode 100644 (file)
index 0000000..249e761
--- /dev/null
+++ b/octave_packages/linear-algebra-2.2.0/@kronprod/times.m
@@ -0,0 +1,67 @@
+## Copyright (C) 2010  Soren Hauberg
+## 
+## 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} times (@var{KP})
+## XXX: Write documentation
+## @end deftypefn
+
+function retval = times (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 ("times: input arguments must be matrices");
+  endif
+  
+  if (!size_equal (M1, M2))
+    error ("times: 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");
+  
+  ## Product of Kronecker Products
+  ## Check if the size match such that the result is a Kronecker Product
+  if (M1_is_KP && M2_is_KP && size_equal (M1.A, M2.A) && size_equal (M1.B, M2.B))
+    retval = kronprod (M1.A .* M2.A, M1.B .* M2.B);
+  elseif (isscalar (M1) || isscalar (M2)) # Product of Kronecker Product and scalar
+    retval = M1 * M2; ## Forward to mtimes.
+  else # All other cases.
+    ## Form the full matrix or sparse matrix of both matrices
+    ## XXX: Can we do something smarter here?
+    if (issparse (M1))
+      M1 = sparse (M1);
+    else
+      M1 = full (M1);
+    endif
+    
+    if (issparse (M2))
+      M2 = sparse (M2);
+    else
+      M2 = full (M2);
+    endif
+    
+    retval = M1 .* M2;
+  endif
+endfunction