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Date:	Mon, 12 Nov 2001 13:45:24 +0300
From:	egor duda <deo AT logos-m DOT ru>
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Reply-To:	egor duda <cygwin AT cygwin DOT com>
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Message-ID:	<13971066568.20011112134524@logos-m.ru>
To:	gilles civario <civario AT mimosa DOT ceng DOT cea DOT fr>
CC:	cygwin AT cygwin DOT com
Subject:	Re: gcc bug: different results between -O0 and -O1
In-Reply-To:	<3BEFA31B.B06D4C37@mimosa.ceng.cea.fr>
References:	<3BEFA31B DOT B06D4C37 AT mimosa DOT ceng DOT cea DOT fr>
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Hi!

Monday, 12 November, 2001 gilles civario civario AT mimosa DOT ceng DOT cea DOT fr wrote:

gc> Wile developing a performance test program for gettimeofday resolution,
gc> I found a strange behavior for gcc under cygwin with the -O flags.
gc> Everywhere else with native compiler or with gcc, the program return constant
gc> results, with or without optimization. (On Sun, Dec, Linux and Fujitsu)
gc> Only with cygwin, the result is divided by 5000 from -O0 to -O1, both with
gc> gcc version 2.95.3-5 (cygwin special) and gcc version 3.0.2.
gc> But it shouldn't. Ok for a little increase, but not for 5000 !

you cannot reliably test float values for equality. you should rethink
the logic of your boucle () function to get reliable results.

Egor.            mailto:deo AT logos-m DOT ru ICQ 5165414 FidoNet 2:5020/496.19


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