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Re: [Bug-gsl] NaN elements returned by gsl_eigen_hermv()

From: Brian Gough
Subject: Re: [Bug-gsl] NaN elements returned by gsl_eigen_hermv()
Date: Thu, 11 Mar 2010 21:38:43 +0000
User-agent: Wanderlust/2.14.0 (Africa) Emacs/22.1 Mule/5.0 (SAKAKI)

At Sun, 07 Mar 2010 00:33:38 -0500,
Beng Heng, Ng wrote:
> I believe there is a bug in gsl_eigen_hermv for at least one Hermitian 
> matrix that results in NaN values in the majority of the elements of 
> evec. There are some 0 elements, though just a few of them.
> There was a fix in GSL v1.13 for issues with NAN values. However, I'm 
> already using GSL v1.13.
> Since it is a 264x264 matrix, I've attached a sample program that reads 
> in the matrix from a file. I compiled it as follows:
>      g++ -lgsl -lgslcblas hermvbug.cpp -o hermvbug.exe
> It will read in the matrix, check that the input matrix is indeed 
> Hermitian, call gsl_eigen_hermv, and finally write the output complex 
> eigenvectors, evec, to "bugoutput.txt".
> I'm using GSL v1.13, gcc v4.3.2, Linux kernel 2.6.26-2-amd64. The 
> processor is Intel Q9300.
> I'll be glad to provide more information, and will definitely appreciate 
> any feedback regarding this issue.

Thanks for the email, sorry for the delay in replying.  I think this
is probably similar to bug 28767
https://savannah.gnu.org/bugs/index.php?28767 with NaNs in the SVD
which is based on the same QR reduction.  I made a fix for that by
scaling intermediate stages, but it needs to be applied to the eigen
routines as well.

Brian Gough

GNU Scientific Library -

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