[SciPy-User] scipy.sparse.linalg.lobpcg broken?

Nico Schlömer nico.schloemer@gmail....
Wed Oct 13 15:30:52 CDT 2010


> Did you use a random matrix as input? If yes, did you set the seed first,
> so that it is testing the same matrix?

I'm using the identity matrix, as in

=========================== *snip* ===========================
from scipy.sparse.linalg import lobpcg
from scipy.sparse import identity
import numpy as np

n = 5
X = np.ones( (n, 1) )
A = identity( n )
lobpcg( A, X, verbosityLevel = 10 )
=========================== *snap* ===========================

Bug report at <http://projects.scipy.org/scipy/ticket/1304>.

Cheers,
Nico



On Wed, Oct 13, 2010 at 9:46 PM, Pauli Virtanen <pav@iki.fi> wrote:
> Wed, 13 Oct 2010 21:23:19 +0200, Nico Schlömer wrote:
>>> It actually works for me:
>>
>> Okay, nice. I tried to run the script on another machine too, where it
>> appears to work alright.
>
> Did you use a random matrix as input? If yes, did you set the seed first,
> so that it is testing the same matrix?
>
>> This exact same code fails on my own machine locally, meaning I'm
>> probably missing some crucial dependencies (of Scipy?). Using Scipy
>> 0.8.0 on Gentoo.
>> Any idea what that could possibly be?
>
> The LOBPCG code in Scipy is pretty self-contained. So I can't guess much
> else than issues with BLAS or LAPACK?
>
> I'd maybe make a copy of lobpcg.py and put some checks in the symeig
> routine. But this is just guessing, I don't know in detail how LOBPCG
> works.
>
> --
> Pauli Virtanen
>
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