[Numpy-discussion] Zero row in SVD's unitary matrix on some Mac's

Rob Beezer beezer at ups.edu
Mon Apr 25 16:34:42 EDT 2011

Thanks for the reply, Pauli.  I suspected this might be the case, but was hoping 
maybe this was something that had been seen before.  I've included your 
suggestions on the bug report for Sage.


On 04/25/2011 10:57 AM, Pauli Virtanen wrote:
> The Numpy routine is a very thin wrapper of LAPACK's ZGESDD, and probably
> cannot have any bugs of this kind, so the problem is most likely with the
> LAPACK and BLAS libraries you use. You will probably be able to reproduce
> the problem also with an equivalent Fortran/C snippet calling LAPACK
> directly.
> Problems like this in BLAS/LAPACK are somewhat difficult to track. You
> could try switching to another BLAS library (or, if you use ATLAS,
> compile it differently) and checking if the problem disappears.

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