[SciPy-user] generalized eig algorithm did not converge

Nils Wagner nwagner at mecha.uni-stuttgart.de
Tue Mar 21 01:52:56 CST 2006


Nils Wagner wrote:
> Hi all,
>
> What is the reason for this message ?
>
> Traceback (most recent call last):
>   File "gh.py", line 4, in ?
>     w = linalg.eigvals(G,H)
>   File "/usr/lib64/python2.4/site-packages/scipy/linalg/decomp.py", line
> 244, in eigvals
>     return eig(a,b=b,left=0,right=0,overwrite_a=overwrite_a)
>   File "/usr/lib64/python2.4/site-packages/scipy/linalg/decomp.py", line
> 121, in eig
>     return _geneig(a1,b,left,right,overwrite_a,overwrite_b)
>   File "/usr/lib64/python2.4/site-packages/scipy/linalg/decomp.py", line
> 72, in _geneig
>     if info>0: raise LinAlgError,"generalized eig algorithm did not
> converge"
> scipy.linalg.basic.LinAlgError: generalized eig algorithm did not converge
>
> Matlab is able to solve this generalized eigenvalue problem without any
> warning.
>
> Afaik, Matlab and scipy's eig is based on LAPACK. So what is the reason
> for the difference ?
>
> Any idea ?
>
> Nils
>   
> ------------------------------------------------------------------------
>
> from scipy import *
> G = io.mmread('G.mtx')
> H = io.mmread('H.mtx')
> w = linalg.eigvals(G,H)
> ------------------------------------------------------------------------
>
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I forgot to ask if someone can reproduce this problem.

Travis, Pearu, Robert K., do you have a clue why Matlab can solve this
eigenproblem while scipy cannot cope with that task.

Nils





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