help-octave
[Top][All Lists]
Advanced

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: False alarm (Re: reshape slowdown?)


From: mavram
Subject: Re: False alarm (Re: reshape slowdown?)
Date: Wed, 23 Feb 2005 13:07:38 +0200
User-agent: Mutt/1.5.5.1+cvs20040105i

On Wed, Feb 23, 2005 at 09:03:19AM +0100, Francesco Potorti` wrote:
> >On Athlon MP 2000 MHz:
> >
> >octave:3> s=rand(3000);
> >octave:4> tic; a=s'; toc
> >ans = 1.9846
> >
> >On Athlon XP 1666 MHz -> 0.9 second.
> 
> >I know what is the problem now. I do not know how to solve it.
> >The problem is that when running in SMP mode the task is bouncing between
> >two CPUs flushing the caches. That can be verified booting in UP mode.
> >So on my system in UP mode:
> >
> >octave:1> a=rand(3000);
> >octave:2> tic; b=a'; toc
> >ans = 0.80099
> >
> >Which is 3 times faster!
> 
> This is awfully slow with respect to what I would (wrongly?) expect.  On
> my very old Pentium II 350 MHz, I get:
> 
> octave> s=rand(3000);
> octave> tic; a=s'; toc
> ans = 2.6762
> octave> version
> ans = 2.1.64
> 
> using the latest Debian package.  Why is my box only three times as slow
> as an Athlon 2000 on matrix transpose?
> 
> -- 
> Francesco Potortì (ricercatore)        Voice: +39 050 315 3058 (op.2111)
> ISTI - Area della ricerca CNR          Fax:   +39 050 313 8091
> via G. Moruzzi 1, I-56124 Pisa         Email: address@hidden
> Web: http://fly.isti.cnr.it/           Key:   fly.isti.cnr.it/public.key
> 
> 
> 
> -------------------------------------------------------------
> Octave is freely available under the terms of the GNU GPL.
> 
> Octave's home on the web:  http://www.octave.org
> How to fund new projects:  http://www.octave.org/funding.html
> Subscription information:  http://www.octave.org/archive.html
> -------------------------------------------------------------
> 
After reading your mails, I cheched the timing on my box (Celeron
 600 MHz with 320 Mbyte RAM/Debian 3.1 testing, kernel 2.4,
 Octave 2.1.57).
 s=rand(3000);
 tic, s'; toc
 ans = 8.18339100014418 !!!
 Is this the normal difference between the two distibutions or
 something is utterly wrong with my computer/operation system
 installation/octave installation ?



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

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



reply via email to

[Prev in Thread] Current Thread [Next in Thread]