Date: Sun, 25 Apr 2010 21:26:12 +0200 From: =?ISO-8859-1?Q?Micha=EBl_Gr=FCnewald?= <michael.grunewald@laposte.net> To: FreeBSD questions <freebsd-questions@freebsd.org> Cc: Leonidas Tsampros <ltsampros@upnet.gr> Subject: Re: Why system gcc that is 4.2.1 produces different code than gcc-4.2.1 compiled from sources? Message-ID: <4BD49754.7070007@laposte.net> In-Reply-To: <87k4rvh0l8.fsf@upnet.gr> References: <4BD3E923.9030606@rawbw.com> <87k4rvh0l8.fsf@upnet.gr>
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Leonidas Tsampros wrote: > I'm pretty sure that a small difference in execution time does not mean > that the produced code is different. Actually, execution time of a process is very sensitive to the environment of this process. See for instance: http://www-plan.cs.colorado.edu/diwan/asplos09.pdf "We see that something external and orthogonal to the program, i.e., changing the size (in bytes) of an unused environment variable, can dramatically (frequently by about 33% and once by almost 300%) change the performance of our program." (The quotation is taken out of the article.) I learned about this in a message from Xavier Leroy to the OCaml mailing list: http://caml.inria.fr/pub/ml-archives/caml-list/2009/12/e261eeb95bec6c5a2791335c84234a05.en.html Cheers, Michaël
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