[gmx-users] mpi run in Gromacs 4.5.3

[Te, Jerez A., Ph.D.]

Hi,
I have been trying to run Gromacs 4.5.3 parallel simulations using openmpi 1.4.2. From my understanding, mdrun_mpi is not used in this version of Gromacs. Our system administrator told me that all mpi related options have been turned on while installing Gromacs. With either commands:
mdrun -np X -deffnm topol -N X (run in an 8-cpu node)
or
mpirun -np X mdrun -deffnm topol -N X (submitted in a number of nodes depending on availability)
I get X identical simulations instead of a parallel run. If X=4, I get 4 identical simulations (the same simulation ran 4 times) instead of 1 parallel simulation in 4 processors. The performance difference between a single-processor run and the X=4 run are also similar (no marked difference in the time it takes to finish the simulation).
Has anyone encountered this problem?
I could provide more details if needed
Thanks,
JT 
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://maillist.sys.kth.se/pipermail/gromacs.org_gmx-users/attachments/20101213/5ac9ffce/attachment.html>