A universal concurrent algorithm for plasma particle-in-cell simulation codes

We have developed a new algorithm for implementation of plasma particle-in-cell (PIC) simulation codes on concurrent processors. This algorithm, termed the universal concurrent PIC algorithm (UC-PIC), has been utilized in a one-dimensional electrostatic PIC code on the JPL Mark III Hypercube parallel computer. To decompose the problem using the UC-PIC algorithm, the physical domain of the simulation is divided into sub-domains, equal in number to the number of processors, such that all sub-domains have roughly equal numbers of particles. For problems with non-uniform particle densities, these sub-domains will be of unequal physical size. Each processor is assigned, a sub-domain, with nearest neighbor sub-domains assigned to nearest neighbor processors. Using this algorithm in the Mark III PIC code, the increase in speed in going from 1 to 32 processors for the dominant portion of code (push time, defined below) was 29, yielding a parallel efficiency of 90%. Although implemented on a hypercube concurrent computer, this algorithm should be also be efficient for PIC codes on other parallel architectures and on sequential computers where part of the data resides in external memory.