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Article #425Re: gcc 3.2 makes slower code
From: Moritz Franosch
Date: Tue, 26 Nov 2002 17:12
Date: Tue, 26 Nov 2002 17:12
29 lines
2120 bytes
2120 bytes
"Jeffrey Cunningham" <jeffrey@cunningham.net> writes: > conclusions: (1) it isn't the I/O. The "slowdown factor" going to gcc 3.2 > is x1.6 with I/O and x1.5 without. And (2) it makes no difference to these > calculations (intensive floating point vector operations) whether I use > -O3 or -O2. Strange, yes. Is this C or C++ code, i.e. do you compile with gcc or g++? But gcc 3.2 should produce faster code in any case (or say up to 5% slower, but not that much slower). > I haven't tried any of the more esoteric optimization tricks yet. But at > this point I'm somewhat alarmed by the loss in performance. I use -fstrict-aliasing -O3 -ffast-math -funroll-loops -march=i686 But don't use -ffast-math if you rely on strict IEEE floating point conformance. Moritz -- Dipl.-Phys. Moritz Franosch http://Franosch.org
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X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: 1041dd,6b8a900e383d587f X-Google-Attributes: gid1041dd,public X-Google-Thread: f65d0,cf9dda410d7d1076 X-Google-Attributes: gidf65d0,public X-Google-ArrivalTime: 2002-11-26 09:12:53 PST Path: arc1-ca.pugleaf.net!archiver1.google.com!news1.google.com!newsfeed.stanford.edu!news-spur1.maxwell.syr.edu!news.maxwell.syr.edu!newsfeed.icl.net!newsfeed.fjserv.net!newsfeed.freenet.de!news-feed1.de1.concert.net!fu-berlin.de!uni-berlin.de!pd9e9485f.dip0.t-ipconnect.DE!not-for-mail From: Moritz Franosch <mail@Franosch.org> Newsgroups: alt.os.linux.suse,gnu.gcc Subject: Re: gcc 3.2 makes slower code Date: 26 Nov 2002 18:12:48 +0100 Lines: 29 Sender: mf@gateway.askos Message-ID: <m37kf0z23z.fsf@gateway.askos> References: <pan.2002.11.24.02.51.19.422739@cunningham.net> <arqit4$4n6$1@condor.gjs.xs4all.nl> <pan.2002.11.25.05.30.25.633705@cunningham.net> <uu3e5l1f71fs38@corp.supernews.com> <pan.2002.11.25.19.02.02.459662@cunningham.net> NNTP-Posting-Host: pd9e9485f.dip0.t-ipconnect.de (217.233.72.95) Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Trace: fu-berlin.de 1038330771 23265873 217.233.72.95 (16 [163233]) User-Agent: Gnus/5.0808 (Gnus v5.8.8) XEmacs/21.4 (Artificial Intelligence)