[gmx-users] Power6 @ 4.7 Ghz vs Xeon E5472 @ 3.00GHz

pim schravendijk pimlists at googlemail.com
Tue Feb 16 17:06:05 CET 2010

Dear Gromacs users,

I have been installing Gromacs on a Power6 4.7 GHz with Infiniband,

before calling configure, I set:

export LDFLAGS="-L/gpfs/schraven/fftw3/lib"
export CPPFLAGS="-I/gpfs/schraven/fftw3/include"
export CC="mpcc_r -q64"
export CFLAGS="-O3 -qstrict -qarch=auto -qtune=auto"
export CXX="mpCC_r -q64"
export CXXFLAGS="-O3 -qstrict -qarch=auto -qtune=auto"
export F77="mpxlf_r -q64"
### O3 gives warning: The NOSTRICT option (default at OPT(3)) has the
potential to alter the semantics of a program.
export FFLAGS="-O3 -qstrict -qnoprefetch -qarch=auto -qtune=auto"
export LIBS="-lmass"
export FLIBS= "-xlf -xlf90"
export OBJECT_MODE=64

I run on both machines at 8 cores (so within the board), and find the 8
power6 cores to be 4-5 times slower (!) than the 8 intel xeon cores.

Does anyone have similar experience between these machines? Are there some
things I should check?
It's a bit useless to use the power6 at all with these kind of speeds, but
they were already here anyway and amazon's 30 day refund on retour has
expired already ;)
Hopefully I'm doing something wrong and the situation can still be improved?

Greetings, Pim
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