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