# [SciPy-dev] Scipy cannot handle singular eigenvalue problems

Nils Wagner wagner.nils at vdi.de
Wed Dec 10 16:49:38 CST 2003

```-------------------

On Wed, 10 Dec 2003, Nils Wagner wrote:

> Scipy cannot handle singular eigenvalue problems. Note, that both
> matrices
> are singular.
>
> from scipy import *
> A = array(([1.,-1.],[-1.,1.]))
> B = array(([1.0,0.0],[0.0,0.0]))
> w,vr = linalg.eig(A,B)
> print w
> print vr
>
> Traceback (most recent call last):
<snip>
> ValueError: matrices are not aligned for copy

This issue is now resolved in CVS. Thanks Travis!

Pearu

It seems to be resolved. However, a second example
doesn't work.
>>> A
array([[ 1.,  0.],
[ 0.,  0.]])
>>> B
array([[ 1.,  0.],
[ 0.,  0.]])
>>> w,vr = linalg.eig(A,B)
Traceback (most recent call last):
File "<stdin>", line 1, in ?
File "/usr/local/lib/python2.3/site-packages/scipy/linalg/decomp.py", line
109, in eig
return _geneig(a1,b,left,right,overwrite_a,overwrite_b)
File "/usr/local/lib/python2.3/site-packages/scipy/linalg/decomp.py", line
68, in _geneig
vr = _make_complex_eigvecs(w, vr, t)
File "/usr/local/lib/python2.3/site-packages/scipy/linalg/decomp.py", line
29, in _make_complex_eigvecs
vnew.real = scipy_base.take(vin,ind[::2],1)
ValueError: matrices are not aligned for copy
>>>
Any comment ?

Nils

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