From help-octave-request at bevo dot che dot wisc dot edu  Fri Feb  4 17:23:40 2000
Subject: ATLAS and octave
From: R Clint Whaley <rwhaley at cs dot utk dot edu>
To: help-octave at bevo dot che dot wisc dot edu
Cc: jwe at bevo dot che dot wisc dot edu
Date: Fri, 4 Feb 2000 18:23:36 -0500

I'm redirecting the following question from where I improperly sent it to
octave-sources.  My apologies.

Hi,

First, let me say octave is a beautiful package, and it is a real lifesaver
for a linear algebra guy like myself . . .  Also, I hope this is the correct
mailing list to bring up the following idea:

We have a free software project known as ATLAS (www.netlib.org/atlas) which
provides optimized BLAS for pretty much arbitrary architectures.  These
BLAS may be orders of magnitude faster than the reference BLAS.  The idea is
that it would be nice if a user could use ATLAS, or some other optimized BLAS,
with octave, thus speeding up all of the lapack-handled routines significantly.
I realize speed is not always important (eg, small problems), but some engineers
use matlab, for instance, to solve quite large problems, where this speedup
would be invaluable.

ATLAS takes a while to install, so I doubt you are interested in including
it in octave, but I thought you might be interesting in facilitating a
user's use of optimized BLAS in order to see these kinds of speedups.
I hacked a previous version of octave to use ATLAS quite a while ago, but
I doubt your average user would be able to do so unless it were made a
little easier.

ATLAS presently includes all the BLAS, and LAPACK's LU and Cholesky
factorization routines.  To give you an idea of the kinds of speedups I'm
talking about, I include a few timings below.  These timings are for a
previous release of ATLAS (which did not have Level 2 or 1 BLAS), but they
can give you an idea of the speedups to be had.  I show the MFLOP rate
for a 500x500 LU factorization, using various configurations an a
266Mhz PII and a 533Mhz DEC ev56:

                               PII266  533 ev56
                              =======  ========
ATLAS LU & BLAS           :       157       441
LAPACK LU, ATLAS BLAS     :       143       330
LAPACK LU, reference BLAS :        68        60

Anyway, if you are interested in pursuing this, please let us know at
atlas at cs dot utk dot edu dot 

Thanks,
Clint



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