[gmx-users] G5 performance tweaks

Pascal Mercier pascal.mercier at ualberta.ca
Wed May 26 00:42:33 CEST 2004

On a 2GHz G5 after trying different compilation flags I managed to got 
a score of 11220 for the Villin test (with 1 CPU), using the build 
scripts below for FFTW and Gromacs (and 11518 using xlf_r, xlc_r, 
xlc++_r).  This only represents a 9% increase in speed compared to the 
1.6 GHz G5 as reported on the benchmark results web page, whereas a 25% 
increase in speed would be expected with a theoretical speed increase 
proportional to the clock speed.  Which flags are recommended for a 
xlf/xlc build of Gromacs on OSX?

Has anyone tried to port Gromacs to Xgrid using the MacMPI related 
fortran and C files available at 

Thanks in advance for any tips.


for FFTW:
#! /bin/tcsh
setenv F77 xlf
setenv FFLAGS "-O3 -qtune=ppc970 -qarch=ppc970 -qalign=4k"
setenv CC xlc
setenv CFLAGS "-O3 -qtune=ppc970 -qarch=ppc970 -qaltivec"
setenv CXX xlc++
setenv CXXFLAGS  "-O3 -qtune=ppc970 -qarch=ppc970 -qaltivec"
./configure --enable-shared --enable-float --enable-type-prefix 
--enable-fortran --enable-threads

for Gromacs:

#! /bin/tcsh
setenv F77 xlf
setenv FFLAGS  "-O3 -qtune=ppc970 -qarch=ppc970 -qalign=4k"
setenv CC xlc
setenv CXX xlc++
./configure   --enable-fortran  --enable-ppc-altivec

Pascal Mercier
Ph. D. Biochemistry
Canadian Institutes of Health Research (CIHR)
Group in Protein Structure and Function
Department of Biochemistry
4-19 Medical Sciences Building
University of Alberta
Edmonton, AB
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