[Pkg-octave-devel] Bug#419556: ambigous results in matrix multipliication

[Alois Schloegl]

Package: Octave2.9
Status: install ok installed
Priority: optional
Section: math
Installed-Size: 26220
Maintainer: Debian Octave Group <pkg-octave-devel at lists.alioth.debian.org>
Architecture: i386
Version: 2.9.10-3
Severity: Important


One expects that a matrix multiplication (A*B)' gives the same result than for (B'*A'). This is not the case for the debian octave package (tested with 2.9.10-3 and 2.1.73-13)

Here is the test script: 

repmat(0,2)*repmat(NaN,2)
repmat(NaN,2)*repmat(0,2)
repmat(0,2)*repmat(inf,2)
repmat(inf,2)*repmat(0,2)
version
octave_config_info('BLAS_LIBS')


octave2.9:27> repmat(0,2)*repmat(NaN,2)
ans =

   NaN   NaN
   NaN   NaN

octave2.9:28> repmat(NaN,2)*repmat(0,2)
ans =

   0   0
   0   0

octave2.9:29> repmat(0,2)*repmat(inf,2)
ans =

   NaN   NaN
   NaN   NaN

octave2.9:30> repmat(inf,2)*repmat(0,2)
ans =

   0   0
   0   0

octave2.9:31> version
ans = 2.9.10
octave2.9:32> octave_config_info('BLAS_LIBS')
ans = -llapack-3 -lblas-3


The problem seems to be in the lapack or blas library. Because this problem disappears (the result is always NaN) when I compile Octave from the sources using Atlas. The octae_config_info says

octave:64> version
ans = 2.9.10+
octave:65> octave_config_info('BLAS_LIBS')
ans = -llapack -lcblas -lf77blas -latlas



A related problem has been also discussed here and here
http://velveeta.che.wisc.edu/octave/lists/bug-octave/2001/104
http://velveeta.che.wisc.edu/octave/lists/bug-octave/2002/293
Obviously, it is not fixed for the debian package. 



Alois 



-- 
"Feel free" - 10 GB Mailbox, 100 FreeSMS/Monat ...
Jetzt GMX TopMail testen: http://www.gmx.net/de/go/topmail