# [Scipy-tickets] [SciPy] #1138: scipy.linalg.decomp.schur error triggered by unrelated scipy.linalg.inv

SciPy Trac scipy-tickets@scipy....
Fri Mar 26 18:53:21 CDT 2010

```#1138: scipy.linalg.decomp.schur error triggered by unrelated scipy.linalg.inv
--------------------------+-------------------------------------------------
Reporter:  cstein06      |       Owner:  somebody
Type:  defect        |      Status:  new
Priority:  normal        |   Milestone:  0.8.0
Component:  scipy.linalg  |     Version:  0.7.0
Keywords:  schur, inv    |
--------------------------+-------------------------------------------------
Hi,

I had the weirdest bug in my code yesterday and have been for a long time
trying to fix it.

I minimized what happens to the following code, where:
1)call schur function to a matrix A and it goes well
2)invert some random unrelated matrix
3)call schur on the same matrix A, but now with error

It happens with other matrices too. I'm using numpy 1.3.0, scipy 0.7.1.

Thank you, I still have no idea how to deal with it.

Carlos

### code begins

from scipy.linalg.decomp import schur

# the matrix 'testshura' is described below.
eps = finfo(float).eps.item()
i = 0+1j
A = A+eps*eps*i*A
schur(A)

pf = randn(6,6)
inv(pf)
schur(A)

### code ends

### matrix used as 'A':

1.000205026940321800e+00 -7.598985000864847600e-04
1.354417450803546800e-04 -2.834813945974936000e-04
1.027364241886627300e-03 -1.751132785374812400e-04
3.130666686080171800e-04 9.988396700866274400e-01 2.068132892990439500e-04
-4.328629968315468400e-04 1.568737748072513400e-03
-2.673898886398420300e-04
-3.465554450703910700e-05 1.284450533630210700e-04
9.999771063870075400e-01 4.791663998840244900e-05
-1.736545799960012900e-04 2.959926148517411600e-05
9.121991180573567400e-05 -3.380915408046700300e-04
6.026029565582238400e-05 9.998738743904914700e-01 4.570915187578423100e-04
-7.791082381298751800e-05
-3.176758536835378800e-05 1.177413096810050200e-04
-2.098581382829571800e-05 4.392359067179063300e-05
9.998408166204494400e-01 2.713265884217382100e-05
1.907558426423412900e-04 -7.070050329939212100e-04
1.260141919459730400e-04 -2.637493990536297400e-04
9.558535641900891800e-04 9.998370756498984300e-01

--
Ticket URL: <http://projects.scipy.org/scipy/ticket/1138>
SciPy <http://www.scipy.org>
SciPy is open-source software for mathematics, science, and engineering.
```