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

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. Rob 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.