Hybrid Parallelization of Hyper-Dimensional Vlasov Code with OpenMP Loop Collapse Directive

Space plasma is a collisionless, multi-scale, and highly nonlinear medium. Computer simulations with the first-principle kinetic equation are essential for space plasma studies. In the present study, a hyper-dimensional Vlasov (collisionless Boltzmann) simulation code, which is a first-principle method for collisionless space plasma, is parallelized with two-level hybrid MPI and OpenMP and is benchmarked on massively-parallel supercomputer systems. The benchmark result shows that the loop “collapse” directive option of the OpenMP reduces threading overhead of multiple loops. It is also shown that the hybrid parallelism with MPI and OpenMP is useful to reduce the communication time of MPI collective communication subroutines.