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From: | Fredrik Lingvall |
Subject: | Re: NaN slowdown with some processors |
Date: | Wed, 04 Jun 2008 12:24:14 +0200 |
User-agent: | Thunderbird 2.0.0.14 (X11/20080505) |
Fredrik Lingvall wrote:
Core2 T7200, 2.00GHz, Octave 3.0.1, Goto BLAS 1.22, Gentoo x86_64, Dell M90 Laptopoctave:1> a=zeros(300,300);tic;b=(1.0+a)*a;toc Elapsed time is 0.082047 seconds. octave:2> a=zeros(300,300);tic;b=(NaN+a)*a;toc Elapsed time is 0.0106151 seconds.
A more thorough test:octave:1> tt=[];for n=1:10000,a=zeros(300,300);tic;b=(1.0+a)*a;t = toc; tt = [tt t]; end
octave:2> mean(tt) ans = 0.0049111 octave:3> std(tt) ans = 6.4211e-04octave:4> tt=[];for n=1:10000,a=zeros(300,300);tic;b=(NaN+a)*a;t = toc; tt = [tt t]; end
octave:5> mean(tt) ans = 0.0048900 octave:6> std(tt) ans = 6.3502e-04Also, Goto BLAS was configured to use both cores (and the THREAD_TIMEOUT was set to 26).
/F
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