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Re: NaN slowdown with some processors
From: |
David Bateman |
Subject: |
Re: NaN slowdown with some processors |
Date: |
Wed, 04 Jun 2008 10:16:04 +0200 |
User-agent: |
Thunderbird 2.0.0.12 (X11/20080306) |
Olli Saarela wrote:
> Hello,
>
> I'm planning to buy a new desktop machine, and since my computations
> utilize NaN values heavily, I'd like to know whether Intel Core 2
> processors suffer from the same slowdown with NaN values as Pentium. For
> details, see http://www.cygnus-software.com/papers/x86andinfinity.html
>
> If someone has Octave on a machine with a Core 2 processor, please run
> the following commands and tell the results. (Or a more detailed test
> from ftp://ftp.cygnus-software.com/pub/specialnumbers.zip)
>
> a=zeros(300,300);tic;b=(1.0+a)*a;toc
> a=zeros(300,300);tic;b=(NaN+a)*a;toc
>
> Below are results from my current machines. Since SSE2 in Pentium isn't
> affected with the slowdown, it seems that for some reason the commands
> above don't utilize SSE2. AMD processors aren't affected.
>
> Pentium M, Octave 3.0.1 MSVC2005 SSE2
> octave-3.0.1.exe:8> a=zeros(300,300);tic;b=(1.0+a)*a;toc
> Elapsed time is 0.0430298 seconds.
> octave-3.0.1.exe:9> a=zeros(300,300);tic;b=(NaN+a)*a;toc
> Elapsed time is 28.8307 seconds.
>
> Pentium 4 (Family 15, Model 2), Octave 3.0.1 MSVC2005 SSE2
> octave-3.0.1.exe:2> a=zeros(300,300);tic;b=(1.0+a)*a;toc
> Elapsed time is 0.0257161 seconds.
> octave-3.0.1.exe:3> a=zeros(300,300);tic;b=(NaN+a)*a;toc
> Elapsed time is 15.7125 seconds.
>
> AMD Turion 64 X2, Octave 3.0.1 MSVC2008 SSE3
> octave-3.0.1.exe:3> a=zeros(300,300);tic;b=(1.0+a)*a;toc
> Elapsed time is 0.0244939 seconds.
> octave-3.0.1.exe:4> a=zeros(300,300);tic;b=(NaN+a)*a;toc
> Elapsed time is 0.0251131 seconds.
>
> Thank you,
> Olli
>
> _______________________________________________
> Help-octave mailing list
> address@hidden
> https://www.cae.wisc.edu/mailman/listinfo/help-octave
>
>
With a Core2 Duo 2.2GHz T7500 processor
octave:3> a=zeros(300,300);tic;b=(1.0+a)*a;toc
Elapsed time is 0.00938201 seconds.
octave:4> a=zeros(300,300);tic;b=(NaN+a)*a;toc
Elapsed time is 0.00932693 seconds.
D.
--
David Bateman address@hidden
Motorola Labs - Paris +33 1 69 35 48 04 (Ph)
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- NaN slowdown with some processors, Olli Saarela, 2008/06/04
- Re: NaN slowdown with some processors, Marc Normandin, 2008/06/04
- Re: NaN slowdown with some processors, Michael Goffioul, 2008/06/04
- Re: NaN slowdown with some processors,
David Bateman <=
- Re: NaN slowdown with some processors, Fredrik Lingvall, 2008/06/04
- Re: NaN slowdown with some processors, Thomas Ilnseher, 2008/06/04
- Re: NaN slowdown with some processors, Olli Saarela, 2008/06/04
- Re: NaN slowdown with some processors, Dmitri A. Sergatskov, 2008/06/05