-------- Original-Nachricht -------- Datum: Mon, 16 Apr 2007 21:38:12 +0200 Von: Thomas Weber <[EMAIL PROTECTED]> An: Alois Schloegl <[EMAIL PROTECTED]>, [EMAIL PROTECTED] Betreff: Re: [Pkg-octave-devel] Bug#419556: ambigous results in matrix multipliication
> 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? Actually, it was the same machine that I used for compiling Octave with Atlas. So atlas-base-dev (which requires also atlas-base) was installed when I tested Octave 2.9.10-3. > > 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 IMHO, this is a bug (and not a feature) of dgemm. Especially, because (A*B)' is not the same as (B'*A'). octave:16> [nan nan]*[0;0] ans = 0 octave:17> [0,0]*[nan nan]' ans = NaN octave:20> [0,0]*[inf inf]' ans = NaN octave:21> [inf inf]*[0;0] ans = 0 > > > 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. > Do you mean that installing atlas3-* besides the debian octave package solves the problem? I do not think so, because the machine I used had Atlas installed. If you mean, that atlas3-* should be installed when the Octave package is compiled for debian, yes I agree to that. Perhaps, the dependency between Octave and atlas-* need to be changed, such that atlas is mandatory instead of one of several alternatives. > Regards > Thomas Regards, Alois -- "Feel free" - 10 GB Mailbox, 100 FreeSMS/Monat ... Jetzt GMX TopMail testen: http://www.gmx.net/de/go/topmail -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]