Fw: better optimization flags for opteron (amd64)

Roberto [khazad-dum] roberto a orson.it
Mar 5 Lug 2005 18:22:44 CEST


Cosa ne pensate ?
Qualcuno ha già provato?
E' realmente così impattante su amd64 ?

Grazie

Begin forwarded message:

Date: Mon, 04 Jul 2005 14:12:57 +0900 (JST)
From: NAKATA Maho <chat95 a mac.com>
To: amd64 a freebsd.org
Cc: netchild a freebsd.org
Subject: better optimization flags for opteron (amd64)


Better optimization flags for Opteron (amd64)

Recently AMD released a guide 
http://www.amd.com/us-en/assets/content_type/white_papers_and_tech_docs/32035.pdf
Compiler Usage  Guidelines for 64-Bit Operating Systems on AMD64
Platforms it has nice flag settings.
recommended flags for opteron/gcc-3.4 is followings:
-pipe -O3 -ffast-math -funroll-all-loops -fpeel-loops -ftracer -
funswitch-loops -funit-at-a-time (see p.19 of 32035.pdf)

and
my benchmark of math/sdpara on Opteron 1.6GHz dual shows:
* scalapack/mpich/blacs is not optimized
     2004.59 real      1979.83 user         9.77 sys

* scalapack/mpich/blacs is optimized
     1261.85 real      1242.63 user         7.76 sys

Hope this helps for you. 
-- NAKATA, Maho (maho a FreeBSD.org)
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-- 
Mi fanno impazzire i cartelli stradali che indicano per "Tutte le
direzioni".  Perche' io generalmente devo andare in una direzione sola,
non in tutte contemporaneamente.


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