Re: [Users] [Possible Spam: 10%] Cactus-built LAPACK, BLAS giving incorrect results

-- David Garrison, Ph.D. Associate Professor and Chair of Physics University of Houston-Clear Lake Bayou 3531 Houston, TX 77058 Tel: 281-283-3796 Fax: 281-283-3709 http://sce.uhcl.edu/garrison For more information about the UHCL Physics Program go to http://www.uhcl.edu/physics or sign up for UHCL newsletters at https://ecommunications.houston.edu/uhcl/join.html "If we knew what it was we were doing, it would not be called research, would it?" - Albert Einstein. -----Original Message----- From: users-bounces@einsteintoolkit.org on behalf of Kelly, Bernard J. (GSFC-660.0)[UNIVERSITY OF MARYLAND BALTIMORECOUNTY] Sent: Fri 5/27/2011 11:09 AM To: users@einsteintoolkit.org Subject: [Possible Spam: 10%] [Users] Cactus-built LAPACK, BLAS giving incorrect results 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. 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). Correct result for "x" is (1,1). Cactus-forced LAPACK (using routine "dgesv") yields (-2,1). I later installed LAPACK (v. 3.3.0) + BLAS by hand on my machine. Linking against these yields the correct answer. I'm on a 32-bit Linux machine, using the Intel 10 compilers. I'd appreciate any insights on this. Thanks, Bernard