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Date:      Mon, 04 Jul 2005 14:12:57 +0900 (JST)
From:      NAKATA Maho <chat95@mac.com>
To:        amd64@freebsd.org
Cc:        netchild@freebsd.org
Subject:   better optimization flags for opteron (amd64)
Message-ID:  <20050704.141257.104030539.chat95@mac.com>

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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@FreeBSD.org)



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