# 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

mpirun -np N dirac.x