Hierarchical Domain Decomposition With Unitary Load Balancing For Electromagnetic Particle-In-Cell Codes

This paper presents a new approach to parallelizing particle-in-cell (PIC) algorithms used in the numeri- cal simulation of three-dimensional plasmas on MIMD multicomputers. Two new concepts are introduced: unitary load balance and hierarchical decomposition. The combined load for particle and field calculations ouer the time step is balanced together to form a single spatial decomposition. The unitary load scheme permits the load to be approzimately balanced while requiring less communication. Decomposition and dynamic bal- ancing as performed in each of the coordinate directions independently (hierarchical), and is particularly efi- cient when load imbalance propagates preferentially in a given direction. The hierarchical decomposition also minimizes the amount of particles that cross bound- ary regions, thereby decreasing communication. A local load balancing method is also introduced which allows rows or columns of processors to perform dynamic load balancing locally and in parallel.