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Date: Fri, 15 Dec 2006 12:51:38 -0800
From: "David O'Brien" <obrien@freebsd.org>
To: Stefan Ehmann <shoesoft@gmx.net>
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Cc: Peter Jeremy <peterjeremy@optushome.com.au>, freebsd-current@freebsd.org,
	Steve Kargl <sgk@troutmask.apl.washington.edu>
Subject: Re: Let's use gcc-4.2, not 4.1 -- OpenMP
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On Fri, Dec 15, 2006 at 07:14:53PM +0100, Stefan Ehmann wrote:
> > CPU: AMD Athlon(TM) XP 2700+ (2166.44-MHz 686-class CPU)
..
> Settings/Compiler           | gcc-3.4 | gcc-4.1 | gcc-4.2
> ----------------------------+---------+---------+---------
> -O2                         |   6.46s |   6.67s |   6.38s
> -O2 -funroll-loops          |   4.44s |   4.16s |   4.02s
> -O2 -march=athlon-xp -fun.. |   4.39s |   4.38s |   4.26s
> -O3                         |   6.14s |   5.23s |   5.16s
> -O3 -funroll-loops          |   4.24s |   4.87s |   4.95s
> -O3 -march=athlon-xp -fun.. |   4.19s |   4.90s |   5.07s

A fine example that -O3 isn't always better than -O2.
I wonder if you're blowing the L2 cache.  IIRC, all Athlon XP 2700+
are the Thoughbread core, which has only 256KB L2.

-- 
-- David  (obrien@FreeBSD.org)