Hydra is a process management system for starting parallel jobs. Hydra
is designed to natively work with existing launcher daemons (such as
ssh, rsh, fork), as well as natively integrate with resource
management systems (such as slurm, pbs, sge).

More information about using Hydra can be found here:
http://wiki.mpich.org/mpich/index.php/Using_the_Hydra_Process_Manager