From help-octave-request at bevo dot che dot wisc dot edu  Mon Dec 18 04:25:52 2000
Subject: Octave and atlas. 
From: Douglas Eck <doug at idsia dot ch>
To: Dirk Eddelbuettel <edd at master dot debian dot org>
CC: "help-octave at bevo dot che dot wisc dot edu" <help-octave@bevo.che.wisc.edu>
Date: Mon, 18 Dec 2000 11:25:40 +0100

I'm cc'ing the octave community on this note to Dirk Eddlbuettel
because his advice was very helpful to me. This info will be
obvious to many of you, but perhaps not to all. 

I wrote to Dirk E. about octave / atlas support and he let me know
that it's already in the Debian woody dist (which I use). He suggested
that I could rebuild atlas for my machine architecture (Athelon) 
and perhaps see an additional speedup.

The speedup from the rebuild was dramatic. Previously I had been
running atlas libs built around an Intel PIII. Now I'm running
with libs built for my athelon.  The following (granted, not very thorough)
simple test program runs ~=50% faster with the Athelon libs than with 
the PIII libs. (Ok, 50% is optimistic overall, but for matrix multiplication
it seems to hold)
  
function [] = testexp()
  a=rand(10,10);
  b=rand(100,100);
  c=rand(100,100);
  tic
  for i=1:10000
    exp(a);
    d=b*c;
  end
  toc

I just thought I'd pass that on, in case it wasn't obvious to 
everyone: it may be worth the time to rebuild atlas around
your specific processor. 

FYI. On my 800Mhz Athelon with 256MB Ram, that testexp()
program now executes in ~=16 seconds using Octave 2.1.32.
It took ~=25 seconds using the PIII libs.

It takes ~=55 seconds in Matlab 5.3.1 for linux!
Octave is >3 times faster in this instance. 

Cheers,
Doug



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