Helsim: a particle-in-cell simulator for highly imbalanced particle distributions

Abstract

Helsim is a 3D electro-magnetic particle-in-cell simulator used to simulate the behaviour of plasma in space. Particle-in-cell simulators track the movement of particles through space, with the particles generating and being subjected to various fields (electric, magnetic and or gravitational). Helsim dissociates the particles data structure from the fields, allowing them to be distributed and load-balanced independently and can simulate experiments with highly imbalanced particle distributions with ease. This paper shows weak scaling results of a highly imbalanced particle setup on up to 32 thousand cores. The results validate the basic claims for scalability for imbalanced particle distributions, but also highlights a problem with a workaround we had to implement to circumvent an OpenMPI bug we encountered.