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[Lapack] INFO=N+2 in xDGGES

Thanks also for your bug report!
Do you have input data that caused this bug to occur,
that you could share with us to try to debug it?
Or did you just notice it by reading the code?
Or did you discover it another way?
Jim Demmel

julie langou wrote:
Thanks for the bug report. I have added your bug report to the LAPACK
Errata file. See: , bug0048. 
I confirmed the problem and we will fix it before next release.
Best wishes,
On Mar 2, 2010, at 1:24 AM, Ondra Kamenik wrote:

Dear lapack developers,

I believe I found a minor little small bug in xDGGES, which should 
return info=n+3 if xTGSEN fails to swap eigenvalues at all, and 
return info=n+2 if swapping slightly changes eigenvalues so that the 
selected eigenvalues are not only in the upper part.

I am referening to dgges.f in lapack 3.2.1 which i downloaded recently.

Indeed, on line 444 the routine sets info=n+3 upon error in dtgsen. 
However, then it checks whether the selected eigenvalues are only in 
the upper part. If dtgsen has failed, it is almost certain that it is 
the case that the selected eigenvalues are not only in the upper 
part, and info=n+2 is set. In this way user does not get info=n+3, 
but only info=n+2.

Many thanks for your great job.

Ondra K.

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Julie Langou; Research Associate in Computer Science
Innovative Computing Laboratory;
University of Tennessee from Denver, Colorado ;-)


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