On 4/25/11 12:57 PM, Pauli Virtanen wrote: > On Mon, 25 Apr 2011 10:16:13 -0700, Rob Beezer wrote: > [clip] >> Many more details and complete transcripts are at: >> http://trac.sagemath.org/sage_trac/ticket/11248 >> >> Any thoughts or advice to help us understand this would be greatly >> appreciated. > > 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.
I was just looking up the documentation for ZGESDD and noticed that the value we have for rwork in the numpy call [1] does not match the Lapack docs. This was changed in Lapack 3.2.2 [2]. I've submitted a pull request: https://github.com/numpy/numpy/pull/78 but I have not tested the change. I doubt this fix will fix the problem on this thread, but it makes sense to make the change anyway. Thanks, Jason [1] https://github.com/numpy/numpy/blob/master/numpy/linalg/linalg.py#L1300 [2] http://icl.cs.utk.edu/lapack-forum/viewtopic.php?f=2&t=1779, or http://www.netlib.org/lapack/lapack-3.2.2.html (bug 0046) _______________________________________________ NumPy-Discussion mailing list NumPy-Discussion@scipy.org http://mail.scipy.org/mailman/listinfo/numpy-discussion
