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[Lapack] INFO=N+2 in xDGGES

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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