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Re: [Help-gsl] ATLAS, SMP, Suse GSL vs. vanilla

From: Brian Gough
Subject: Re: [Help-gsl] ATLAS, SMP, Suse GSL vs. vanilla
Date: Tue, 27 Sep 2005 17:56:05 +0100

Joe Georger writes:
 > I have a couple of questions regarding the use of GSL with ATLAS.  I am 
 > working on a dual Opteron running Suse 9.3 Pro.  I installed GSL v1.6.5 
 > from the Suse dvd.  I downloaded and installed ATLAS 3.7.11.  I wrote a 
 > test code to do a QR decompostion with N=1000.  


I don't know what options SUSE uses for building GSL but it sounds
like they are good ones (perhaps there is some way to find out by
installing the source rpm?) .  Maybe they use -msse2 -mfpmath.

To make use of BLAS in the QR decomposition you will need to build the
library itself with CFLAGS=".... -DUSE_BLAS" (look in
linalg/householder.c to see why)

The USE_BLAS is not documented (sorry) -- right now not all of the
library is using BLAS.  Where there was existing non-BLAS code with
"for" loops which were working it was a case of "if it ain't broke,
don't fix it".

I will change USE_BLAS to be the default next time.  There are other
routines which also need to be blas-ified.

Brian Gough

Network Theory Ltd,
Publishing Free Software Manuals ---

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