Actually I had a much differnt results,

gromacs-3.3.1 one node dual core dual socket opt2218 openmpi-1.2.7 pgi/7.2
mpich2 gcc

19M OpenMPI
    M  Mpich2

So for me OpenMPI+pgi was faster, I don't know how you got such a low mpich2 number.

On the other hand if you do this preprocess before you run:

grompp -sort -shuffle -np 4
mdrun -v

With -sort and -shuffle  the OpenMPI run time went down,

12M OpenMPI + sort shuffle

I think my install of mpich2 may be bad, I have never installed it before, only mpich1, OpenMPI and LAM. So take my mpich2 numbers with salt, Lots of salt.

On that point though -sort -shuffle may be useful for you, be sure to understand what they do before you use them.
Read:
http://cac.engin.umich.edu/resources/software/gromacs.html

Last, make sure that your using the single precision version of gromacs for both runs. the double is about half the speed of the single.

Brock Palen
www.umich.edu/~brockp
Center for Advanced Computing
bro...@umich.edu
(734)936-1985



On Oct 10, 2008, at 1:15 AM, Sangamesh B wrote:



On Thu, Oct 9, 2008 at 7:30 PM, Brock Palen <bro...@umich.edu> wrote:
Which benchmark did you use?

Out of 4 benchmarks I used d.dppc benchmark.

Brock Palen
www.umich.edu/~brockp
Center for Advanced Computing
bro...@umich.edu
(734)936-1985



On Oct 9, 2008, at 8:06 AM, Sangamesh B wrote:



On Thu, Oct 9, 2008 at 5:40 AM, Jeff Squyres <jsquy...@cisco.com> wrote:
On Oct 8, 2008, at 5:25 PM, Aurélien Bouteiller wrote:

Make sure you don't use a "debug" build of Open MPI. If you use trunk, the build system detects it and turns on debug by default. It really kills performance. --disable-debug will remove all those nasty printfs from the critical path.

You can easily tell if you have a debug build of OMPI with the ompi_info command:

shell$ ompi_info | grep debug
 Internal debug support: no
Memory debugging support: no
shell$
Yes. It is "no"
$ /opt/ompi127/bin/ompi_info -all | grep debug
 Internal debug support: no
Memory debugging support: no

I've tested GROMACS for a single process (mpirun -np 1):
Here are the results:

OpenMPI : 120m 6s

MPICH2 :  67m 44s

I'm trying to bulid the codes with PGI, but facing problem with compilation of GROMACS.

You want to see "no" for both of those.

--
Jeff Squyres
Cisco Systems



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