Parallel Solver Based on the Three-Dimensional Characteristics Method: Design and Performance Analysis

Recent advances in parallel software development for solving three-dimensional (3-D) neutron transport problems using the characteristics method are presented. The characteristics method solves the transport equation by collecting local angular fluxes along neutron paths. In order to be able to solve large 3-D transport problems in a reasonable time frame, the characteristics solver needs to be accelerated. After applying adequate numerical acceleration techniques, the only issue is to parallelize the solver. The parallelization of this solver is based on distributing a group of tracks, generated by a ray-tracing procedure, on several processors. Different distributing schemes and load-balancing techniques based on a calculation load model are presented. A message-passing model is used to communicate the local solutions between processes participating in solving a problem. Both analytical models of this parallel algorithm and performance analysis are presented and illustrated by several examples.