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<TITLE>RE: [Possible Spam: 10%] [Users] Cactus-built LAPACK, BLAS giving incorrect results</TITLE>
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<P><FONT SIZE=2>Hi,<BR>
<BR>
I doubt this helps but (-2,1) is a non-normalized eigenvector of the system. Maybe your forced LAPACK was doing the wrong operation.<BR>
<BR>
-DG<BR>
<BR>
--<BR>
David Garrison, Ph.D.<BR>
Associate Professor and Chair of Physics<BR>
University of Houston-Clear Lake<BR>
Bayou 3531<BR>
Houston, TX 77058<BR>
<BR>
Tel: 281-283-3796<BR>
Fax: 281-283-3709<BR>
<A HREF="http://sce.uhcl.edu/garrison">http://sce.uhcl.edu/garrison</A><BR>
<BR>
For more information about the UHCL Physics Program go to <A HREF="http://www.uhcl.edu/physics">http://www.uhcl.edu/physics</A> or sign up for UHCL newsletters at <A HREF="https://ecommunications.houston.edu/uhcl/join.html">https://ecommunications.houston.edu/uhcl/join.html</A><BR>
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"If we knew what it was we were doing, it would not be called research, would it?" - Albert Einstein.<BR>
<BR>
<BR>
<BR>
-----Original Message-----<BR>
From: users-bounces@einsteintoolkit.org on behalf of Kelly, Bernard J. (GSFC-660.0)[UNIVERSITY OF MARYLAND BALTIMORECOUNTY]<BR>
Sent: Fri 5/27/2011 11:09 AM<BR>
To: users@einsteintoolkit.org<BR>
Subject: [Possible Spam: 10%] [Users] Cactus-built LAPACK, BLAS giving incorrect results<BR>
<BR>
Hi all. I recently needed to use a LAPACK routine in a Cactus thorn. Since my local machine's installation of LAPACK & BLAS was old, I decided to force an installation by including the thorns "ExternalLibraries/[BLAS,LAPACK]". This seemed to work, with the resulting .a files ending up in configs/<my config name>/scratch/external/LAPACK, etc. Compiling and running my cactus executable, however, I found the LAPACK gave completely wrong results.<BR>
<BR>
For a much simpler test case that (see attached F90 standalone program), consider the 2x2 system A x = b, where A = (3, 2\\2, 6), and b = (5, 8).<BR>
<BR>
Correct result for "x" is (1,1).<BR>
<BR>
Cactus-forced LAPACK (using routine "dgesv") yields (-2,1).<BR>
<BR>
I later installed LAPACK (v. 3.3.0) + BLAS by hand on my machine. Linking against these yields the correct answer.<BR>
<BR>
I'm on a 32-bit Linux machine, using the Intel 10 compilers.<BR>
<BR>
I'd appreciate any insights on this. Thanks,<BR>
<BR>
Bernard<BR>
<BR>
</FONT>
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