# [Scipy-tickets] [SciPy] #1159: Wrong eigenvalues generated by scipy.linalg.eigh

SciPy Trac scipy-tickets@scipy....
Tue Apr 20 19:52:37 CDT 2010

```#1159: Wrong eigenvalues generated by scipy.linalg.eigh
------------------------------------------------+---------------------------
Reporter:  ysr                                 |       Owner:  somebody
Type:  defect                              |      Status:  new
Priority:  highest                             |   Milestone:  0.8.0
Component:  scipy.linalg                        |     Version:  0.7.0
Keywords:  eigenvalue, hermitian, eigenvector  |
------------------------------------------------+---------------------------
Wrong eigenvalues are generated by the following example. I have to attach
the example matrix in order to reproduce the error.

{{{
import scipy.linalg
import scipy.io
# let us compute the first (smallest) 5 eigenvectors
d,v= scipy.linalg.eigh(L,eigvals=(0,4))
# let us check if the eigenvectors are orthogonal
scipy.multiply(v[:,0],v[:,1]).sum()
# answer is zero (to a floating point error). Good!
# now let us compute the first (smallest) 2 eigenvectors
d,v= scipy.linalg.eigh(L,eigvals=(0,1))
# let us check if the eigenvectors are orthogonal
scipy.multiply(v[:,0],v[:,1]).sum()
# they are not orthogonal!! the second eigenvector was not calculated
correctly!
}}}

--
Ticket URL: <http://projects.scipy.org/scipy/ticket/1159>
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```