[MPICH] mpirun vs. mpiexec

[Anthony Chan]

On Tue, 5 Jun 2007, Steve Young wrote:

> Hello,
> 	I am trying to understand the differences of when to use mpirun vs.
> using mpiexec.
>
> Currently, we have a cluster (x86_64 with 38 nodes - 4cpu's per node)
> that is set up with mpich2-1.0.5 and running a ring that is started
> across all the nodes by root.
>
> We are also using PBS (torque-2.0.0p7) to manage the resources.
>

Have you tried to start the mpd ring as a regular user ?  i.e. do
mpdboot in your pbs script ?  If you don't want to start mpd within
the pbs script, you may want to consider using Pete Wyckoff's mpiexec
from osc.edu with mpich2+torque.

> Our main problem is with using the sander.MPI program from the Amber9
> software. But I have been able to produce the same results using the
> simple bounce program.
>
>
> Now first I use mpirun and the program will run as expected:
>
> mpirun -np 8 sander.MPI -O......
>
> However, using mpirun the the program doesn't go to the proper nodes
> that PBS allocates to the job. when I try to give mpirun the -
> machinefile argument mpirun complains about this as it doesn't appear to
> know about this one.

In mpich2, mpirun points to mpiexec.  Anyway, you should use mpiexec that
comes with the process manager.

A.Chan