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Re: [Bug-gnubg] compiling with optimization

From: Holger
Subject: Re: [Bug-gnubg] compiling with optimization
Date: Wed, 19 Nov 2003 00:15:07 +0100

At 22:09 18.11.2003, Achim Mueller wrote:
I just did a small test with different optimization flags.

machine:toshiba satellite 2430-101, 512mb RAM, 2,5 ghz pentium4
os:     SuSE-Linux 9.0, glibc-2.3.2-88, gcc-3.3.1

without opt:    CFLAGS=""
i686:           CFLAGS="-march=i686 -mcpu=i686"
i686-O2:        same + O2
i686-O3:        same + O3
pentium4:       CFLAGS="-march=pentium4 -mcpu=pentium4"
pentium4-O2:    same + O2
pentium4-O3:    same + O3
pentium4-all:   same + -pipe -fomit-frame-pointer -fforce-addr
                       -falign-functions=4 -ffast-math

Results (gnubg -t "calibrate"):

without opt:    10954   12642
i686:           10985   11272
i686-O2:        22119   22125
i686-O3:        22386   22438
pentium4:       10996   11186
pentium4-O2:    23307   23255
pentium4-O3:    22849   22783
pentium4-all:   22815   22852

Interesting: If you don't use "-O" you get only half of the maximum.


Same like we got in former tests. See e.g. http://mail.gnu.org/archive/html/bug-gnubg/2003-01/msg00424.html . However it's a bit strange that pentium4-O3 does worse than pentium4-O2. In my experience it's most important to switch on -O2 (or -O3). All processor specific features (like MMX or SSE) hardly make a difference.



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