Hybrid Ordered Particle Simulation (HOPS) code for plasma modelling on vector-serial, vector-parallel, and massively parallel computers Original Research Article

The Hybrid Ordered Particle Simulation (HOPS) code has been developed to provide a more efficient method for carrying out particle-in-cell (PIC) simulations of plasma phenomena. Conventional PIC methods store the particle attributes in tables that tend to have a random spatial order, which was appropriate for older serial-scalar computers. Problems associated with excessive accessing of memory, indirect indexing, and with many-to-one mappings in the deposition phase can make these codes inefficient on vector-serial, vector-parallel, and massively parallel machines. In the HOPS code we employ a sorting scheme to keep the particles ordered with respect to their spatial positions. By doing so, we have reduced memory accesses, recovered substantial direct indexing, and most importantly removed the many-to-one mapping problem. A low overhead sorting and reordering scheme is presented which allows HOPS to be most efficient on vector-serial machines and which scales linearly to various kinds of parallel computers. This paper focuses on the Cray C-90 vector-parallel computer but also discusses aspects of a massively parallel implementation.