[SciPy-user] Disable ATLAS

Nils Wagner dr.nwagner at web.de
Sat Feb 21 22:57:20 CST 2004


SciPy Users List <scipy-user at scipy.net> schrieb am 21.02.04 21:03:36: 
 
 
 
On Sat, 21 Feb 2004, Nils Wagner wrote: 
 
> Please can you run lu.py   
 
When I set 
 
  force_clapack=0 
 
then the output of lu.py is 
 
--------------- 
X 
 
[[ 1.28518872-0.09428482j -0.46708202-0.37104511j] 
 [-0.31203795+0.19175932j  0.73496379-0.19732829j]] 
 
inv(A) 
 
[[ 0.91414361+0.3727972j  -0.46708202-0.37104511j] 
 [-0.50936624-0.54320447j  0.73496379-0.19732829j]] 
 
Identity ??? 
 
[[  1.00000000e+00 +2.90295132e-17j  -1.99086624e-17 -3.05202912e-17j] 
 [  7.09610322e-17 +1.95427442e-16j   1.00000000e-00 +2.33103467e-18j]] 
 
Identity ??? 
 
[[  1.00000000e+00 +1.72794721e-17j  -1.99086624e-17 -3.05202912e-17j] 
 [ -2.36085023e-17 +1.00000000e+00j   1.00000000e-00 +2.33103467e-18j]] 
----^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^---------- 
 
How about -2.36085023e-17 +1.00000000e+00j ? 
The imaginary part should be zero ! 
 
Nils 
 
Everything is correct up to round-off errors. So, check again that ATLAS  
is not being used. For the record, with force_lapack=1 the results are  
incorrect. 
 
As for a possible Atlas bug, I haven't created a simple C program that 
would demonstrate the bug and is necessary to file a bug report to Atlas 
people. Any takers? 
 
Pearu 
 
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