How to define an alternative MPI launcher

The pam script by default launches MPI runs with mpirun. If you cannot use mpirun because you are on a system which does not support it or which offers alternative MPI launchers (SGI, Cray), you can define your own DIRAC_MPI_COMMAND like this:

$ export DIRAC_MPI_COMMAND="mpirun -np 8"
$ export DIRAC_MPI_COMMAND="mpprun"
$ export DIRAC_MPI_COMMAND="aprun -n 24"

This will then launch:

$DIRAC_MPI_COMMAND dirac.x

instead of:

mpirun -np N dirac.x

Note that --mpi overrides DIRAC_MPI_COMMAND.

Passing arguments to MPI launcher

You can pass arguments to the MPI launcher, for example:

./pam --scratchfull="/tmp/milias/TEST" --noarch --mpiarg="-x PATH -x LD_LIBRARY_PATH --wdir '/tmp/milias/TEST'" --mpi=4 --inp=cc.inp  --mol=N2.ccpVDZ.mol

Note that you have provide proper workdir (the --wdir flag) for your MPI launcher, otherwise it ends with error.

Concerning passing of environmental variables (through the -x flag), if the variable is not defined, the MPI launcher gives warning (like Warning: could not find environment variable "LD_LIBRARY_PATHx").