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OK, so maybe not heroic. But my attempts at getting MPI running are much like an uphill battle.

I managed only partly, so far, so here are some notes:

  • I used passwordless-hostbased-ssh logins between the nodes
  • I used Torque as the batch system
  • I used the RHEL4 provided openmpi (that does not include the tm module, hence the ssh stuff)
  • It worked with torque and mpirun
  • ... but not with mpi-start.
  • It does not yet work with CREAM, als all the processes are run on the same node.

One thing that I had forgotten was to set the MPI_*_PATH variables that mpi-start needs. It had a fallback to /opt/i2g/openmpi and that did not distribute the work according to plan. After I straightened this out, I got the same result: everything ran on the same node.

mpi-start is supposed to do the right thing, but no. The debug message I got was clarifying things:

found openmpi and PBS, don't set machinefile

which means that the call to mpirun (or mpiexec) does not include the -machinefile which it needs. You wouldn't need it if the openmpi came with the PBS startup stuff, but in this case it is no true.