better optimization flags for opteron (amd64)

[NAKATA Maho]

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)