Running on a Dedicated System

If your system has sufficient capacity for running your MPI job, you can commit processors aggressively to your job. At a minimum, the CPU load should not exceed the number of physical processors. The CPU load for your job is the number of MPI processes in the job, but the load is greater if your job is multithreaded. The load on the system must also be shared with any other jobs are running on the same system. You can check the current load can be checked with the mpinfo command.

To run your job more aggressively on a dedicated system, set the MPI_SPIN and MPI_PROCBIND environment variables:

% setenv MPI_SPIN 1

Use this only if you will leave at least one processor per node free to service system daemons. Profiling with Prism introduces background daemons that cause a slight but noticeable load, so you must be careful to avoid overloading when attempting to profile a code with this setting.

% setenv MPI_PROCBIND 1

Set the MPI_PROCBIND variable only if there are no other MPI jobs running and your job is single-threaded.