[gmx-users] Question about starting Gromacs 4.5.4 parallel runs using mpirun

[Andrew DeYoung]

Hi,

Typically, I use Gromacs 4.5.5 compiled with automatic threading. As you
know, automatic threading is awesome because it allows me to start parallel
runs without calling mpirun. So on version 4.5.5, I can start a job on eight
CPUs using simply the command:

mdrun -s topol.tpr -nt 8

However, now I am using a different node on my department's cluster, and
this node instead has Gromacs 4.5.4 (compiled without automatic threading).
So, I must use mpirun to start parallel runs. I have tried this command:

mpirun -machinefile mymachines -np 8 mdrun -s topol.tpr

where mymachines is an (extensionless) file containing only the text "c60
slots=8". (c60 is the name of the node that I am using.)

I get this error message:

"Missing: program name. Program mdrun either does not exist, is not
executable, or is an erroneous argument to mpirun."

This is strange, because mdrun is, I think, in my path. For example, if I
type "mdrun -h", I get the manual page for mdrun (version 4.5.4).

Then I tried the command "which mdrun", and it gave me this output:

/usr/local/gromacs/bin/mdrun

So, next I tried to call mdrun via mpirun using the specific path for mdrun:

mpirun -machinefile mymachines -np 8 /usr/local/gromacs/bin/mdrun -s
topol.tpr

This starts running my simulation, but when I look in "top", the simulation
is only running on a single CPU; there is only one entry for mdrun in "top",
and it has only %CPU=100 (not eight different entries for mdrun, nor one
entry with %CPU=800). Also, the simulation is going at the speed I would
expect for running on a single CPU -- it is very slow, so I am convinced
that, as "top" suggests, mdrun is running on only one CPU.

Strangely, my colleagues are able to run jobs in parallel using the exact
commands that I described above. So apparently something is wrong with my
user ID, although there are no error messages (except the error message
about "Missing: program name" that I described).

If you have time, do you have any suggestions for other things that I can
try? Do you think that something could be wrong with my bashrc file?

Thanks for your time!

Andrew DeYoung
Carnegie Mellon University