From help-octave-request at bevo dot che dot wisc dot edu  Mon Dec  6 11:43:28 1999
Subject: speed issues (was Re: Dot product (nx1).*(nxm))
From: Mike Miller <mbmiller at taxa dot psyc dot missouri dot edu>
To: Help-Octave List <help-octave at bevo dot che dot wisc dot edu>
Date: Mon, 6 Dec 1999 11:43:26 -0600 (CST)

This was my result:

octave:1> p=rand(100,1);
octave:2> q=ones(1,50);
octave:3> p2=p*q;
octave:4> t0=cputime; for i=1:1000, p2=p*q; end , cputime-t0
ans = 2.4600


But Michael Hanke <hanke at nada dot kth dot se> had this result:


octave:1> p=rand(100,1);
octave:2> q=ones(1,50);
octave:3> p2=p*q;
octave:4> t0=cputime; for i=1:1000, p2=p*q; end , cputime-t0
ans = 0.34773


            Mike Miller     Michael Hanke
            ===========     =============
version       2.0.14           2.0.13
OS          Solaris 2.6     Solaris 2.5.1
machine     Ultra 2 2200       Ultra 1
CPU speed     200 MHz          170 MHz


Michael Hanke wrote:

"Octave: The Fortran stuff is completely replaced by the Sun Performance
Library which is well tuned to the hardware. So the break-even appears at
rather high dimensions. Caching effects?"


Of course I'm very concerned that I have done a poor job of compiling
Octave on my Sun.  I was happy that I could make it work, but now I think
I should find a way to make it run fast.  I compiled using gcc.  Was that
my mistake?  Do I have to buy software from Sun that will allow me to
better optimize Octave?  I'm pretty naive about compiler issues, so keep
it simple if you can!  :-)  (For example, I don't know what the Sun
Performance Library is and I don't know which Fortran stuff is replaced by
that library.)

Thanks in advance for any suggestions,

Mike

-- 
Michael B. Miller
University of Missouri--Columbia
http://taxa.psyc.missouri.edu/~mbmiller/



-----------------------------------------------------------------------
Octave is freely available under the terms of the GNU GPL.

Octave's home on the web:  http://www.che.wisc.edu/octave/octave.html
How to fund new projects:  http://www.che.wisc.edu/octave/funding.html
Subscription information:  http://www.che.wisc.edu/octave/archive.html
-----------------------------------------------------------------------