Re: Let's use gcc-4.2, not 4.1 -- OpenMP

From: Luigi Rizzo <rizzo_at_icir.org>
Date: Fri, 15 Dec 2006 06:05:32 -0800
On Fri, Dec 15, 2006 at 01:39:48PM +0000, Poul-Henning Kamp wrote:
> In message <200612151250.10033.shoesoft_at_gmx.net>, Stefan Ehmann writes:
> 
> >Settings/Compiler           | gcc-3.4 | gcc-4.1 | gcc-4.2
> >----------------------------+---------+---------+---------
> >-O2                         |  13.1bn |  13.8bn |  13.5bn
> >-O2 -funroll-loops          |   9.6bn |   9.3bn |   9.2bn
> >-O2 -march=athlon-xp -fun.. |   9.7bn |  10.6bn |  10.7bn
> >-O3                         |  11.5bn |   9.5bn |   9.6bn
> >-O3 -funroll-loops          |   8.4bn |   9.2bn |   9.4bn
> >-O3 -march=athlon-xp -fun.. |   8.8bn |  10.6bn |  11.1bn
> 
> I love benchmarks.
> 
> It's great when people benchmark things.
> 
> Unfortunately, that is not what you have done, because you have
> not indicated what the standard deviation on your numbers are,
> so they are totally worthless.

in general, you are totally right.

but note that in this specific case, these seem to be
the numbers of retired instructions, not cycles or times.

So they should be rather deterministic (apart from background noise
due to races in getting locks, interfering kernel activity etc. -
which in truth the SD would help characterising :)

	cheers
	luigi

> -- 
> Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
> phk_at_FreeBSD.ORG         | TCP/IP since RFC 956
> FreeBSD committer       | BSD since 4.3-tahoe    
> Never attribute to malice what can adequately be explained by incompetence.
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Received on Fri Dec 15 2006 - 13:05:32 UTC

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