Improving the Dynamic Creation of Processes in MPI-2

The MPI-2 standard has been implemented for a few years in most of the MPI distributions. As MPI-1.2, it leaves it up to the user to decide when and where the processes must be run. Yet, the dynamic creation of processes, enabled by MPI-2, turns it harder to handle their scheduling manually. This paper presents a scheduler module, that has been implemented with MPI-2, that determines, on-line (

i.e.

during the execution), on which processor a newly spawned process should be run. The scheduler can apply a basic Round-Robin mechanism or use load information to apply a list scheduling policy, for MPI-2 programs with dynamic creation of processes. A rapid presentation of the scheduler is given, followed by experimental evaluations on three test programs: the Fibonacci computation, the

N

-Queens benchmark and a computation of prime numbers. Even with the basic mechanisms that have been implemented, a clear gain is obtained regarding the run-time, the load balance, and consequently regarding the number of processes that can be run by the MPI program.