[Numpy-discussion] SVD errors

[mtrumpis at berkeley.edu]

Hello list.. I've run into two SVD errors over the last few days. Both
errors are identical in numpy/scipy.

I've submitted a ticket for the 1st problem (numpy ticket #990). Summary
is: some builds of the lapack_lite module linking against system LAPACK
(not the bundled dlapack_lite.o, etc) give a "LinAlgError: SVD did not
converge" exception on my matrix. This error does occur using Mac's
Accelerate framework LAPACK, and a coworker's Ubuntu LAPACK version. It
does not seem to happen using ATLAS LAPACK (nor using Octave/Matlab on
said Ubuntu)

Just today I've come across a negative singular value cropping up in an
SVD of a different matrix. This error does occur on my ATLAS LAPACK based
numpy, as well as on the Ubuntu setup. And once again, it does not happen
in Octave/Matlab.

I'm using numpy 1.3.0.dev6336 -- don't know what the Ubuntu box is running.

Here are some npy files for the two different cases:

https://cirl.berkeley.edu/twiki/pub/User/MikeTrumpis/noconverge_operator.npy
https://cirl.berkeley.edu/twiki/pub/User/MikeTrumpis/negsval_operator.npy

Mike