On the adequacy of message-passing parallel supercomputers for solving neutron transport problems

A coarse-grained, static-scheduling parallelization of the standard iterative scheme used for solving the discrete-ordinates approximation of the neutron transport equation is described. The parallel algorithm is based on a decomposition of the angular domain along the discrete ordinates, thus naturally producing a set of completely uncoupled systems of equations in each iteration. Implementation of the parallel code on the Intel iPSC/2 hypercube, and solutions to test problems are presented as evidence of the high speedup and efficiency of the parallel code. The performance of the parallel code on the iPSC/2 is analyzed, and a model for the CPU time as a function of the problem size and the number of participating processors is developed and validated against measured CPU times. It is concluded that parallel computers with a few hundred processors are capable of producing large speedups at very high efficiencies in very large three-dimensional problems