[Numpy-discussion] wired error message in scipy.sparse.eigen function: Segmentation fault

[David Cournapeau]

On Sat, Feb 6, 2010 at 9:25 AM, Jankins <andyjian430074 at gmail.com> wrote:
> This problem keeps bothering me for days.
> If you need more sample to test it, I got one more. I tested it this
> morning. And the "segmentation  fault" happened at a specific place.
> I guess, finally, I have to refer to the original eigenvalue algorithm or
> Matlab.

Hm, I found something which makes valgrind happy, but I am not sure
whether the fix is right. There is definitely something wrong in
vector sizes (the crash happens within dnaitr, and some arrays are
accessed outside bounds), but the input arguments constraints are all
valid if I read the ARPACK sources correctly. It just seems that your
data uncover a corner case not well handled by ARPACK.

Making the buffers big enough seems to cause the algorithm not to
converge for your data, though (to see by yourself, try making ncv
argument to eigen biffer than its default 2k+1 value). Since Matlab
also uses ARPACK, I would be interested in knowing how matlab behaves
for your data,

cheers,

David