better optimization flags for opteron (amd64)

[Hugo Silva]

Hmm, would this be safe to use on all ports? Sometimes speed is nice, 
but if it breaks stability...



NAKATA Maho wrote:

>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 at FreeBSD.org)
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>  
>