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

[Alois Schlögl <alois.schloegl@gmx.net>]

Thomas Weber wrote:
> Hi, 
>
> Am Montag, 16. April 2007 17:32 schrieb Alois Schloegl:
>   
> > 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')
> >     
>
> I take it for granted that you didn't have ATLAS installed. Is this correct?
>
>   

The answer in my last mail was just a guess (I did not have access to 
the same machine). Now, I was able to check this on a different machine. 
Yes, I can confirm that the result depends on the fact whether atlas is 
installed or not.


> Unless I'm mistaken, the reference implementation of dgemm is supposed to do 
> exactly this, see
> http://velveeta.che.wisc.edu/octave/lists/bug-octave/2002/310
>
>   
> > 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. 
> >     
>
> I guess the best "fix" for this problem is installing one of the atlas3-* 
> packages.
>   
Yes, I agree. Setting the dependences accordingly would solve the 
problem for the debian users of octave.

> Regards
> 	Thomas    
>   

Regards,
  Alois