[OT] gcc 2.95.2 vs. 3.0 (fwd)

From: Sasi Peter (sape@iq.rulez.org)
Date: Sun Jun 24 2001 - 04:54:25 EST

first of all, if you are not interested in compiler comparision, just

I though posting a little demonstration of how well performing code gcc
2.95.2 generates (vs. gcc 3.0) won't hurt. Also shown, that further
optimatizations are anything but impossible (using Intel's commercial c

I know opendivx code is not like kernel code at all, but on the other hand
it is well suited for benchmark testing.

Maybe this will cool down thoose a bit, who were to move to gcc 3.0 as
fast as possible, for the _way_ better generated code...

SaPE - Peter, Sasi - mailto:sape@sch.hu - http://sape.iq.rulez.org/

---------- Forwarded message ---------- Date: Sun, 24 Jun 2001 04:31:56 +0200 (CEST) From: Arpi <arpi@thot.banki.hu> Reply-To: mplayer-users@lists.sourceforge.net To: mplayer-users@lists.sourceforge.net Subject: [Mplayer-users] gcc 2.95.2 vs. 3.0


Just compiled and try gcc 3.0 stable. And the results is very big surprise! It makes *SLOWER* code!

test file: (opendivx with postprocessing, this stuff is written in C) # mplayer -osdlevel 0 -nosound -benchmark 1800.avi -vo null -pp 15 VIDEO: [divx] 640x352 24bpp 23.98 fps 1865.1 kbps (227.7 kbyte/s)

hardware: celeron-2 600 @ 900MHz (100MHz FSB), 256MB RAM (PC133, at 2/2/2) (sse,mmx,mmxext enabled)

gcc 2.95.2 result: (flags: -O4 -march=i686 -mcpu=i686 -pipe -ffast-math) BENCHMARKs: V: 5.087s VO: 0.001s A: 0.000s Sys: 0.013s = 5.101s BENCHMARK%: V: 99.7160% VO: 0.0258% A: 0.0000% Sys: 0.2582% = 100.0000%

gcc 3.0 result: (flags: -O4 -march=i686 -mcpu=i686 -pipe -ffast-math) BENCHMARKs: V: 5.194s VO: 0.001s A: 0.000s Sys: 0.013s = 5.208s BENCHMARK%: V: 99.7309% VO: 0.0221% A: 0.0000% Sys: 0.2471% = 100.0000%

yes, speed diff isn't big, but i was prepared for big speed boost by 3.0, and then i got speed loss! :(

if i recompile C-only parts of decore with intel's commercial C compiler (free beta available for linux), it's about 15% faster:

icc result: (optim. flags: -O2 -fp -rcd -tpp6 -xiMK) BENCHMARKs: V: 4.415s VO: 0.001s A: 0.000s Sys: 0.013s = 4.429s BENCHMARK%: V: 99.6676% VO: 0.0290% A: 0.0000% Sys: 0.3034% = 100.0000%

A'rpi / Astral & ESP-team

-- mailto:arpi@thot.banki.hu http://esp-team.scene.hu

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