Development and parallelization of the three-dimensional characteristics solver MCI of DRAGON

In this paper, recent advances in parallel software development for solving neutron transport problems are presented. The method of characteristics is based on the resolution of the differential transport equation following the tracking lines in order to collect the local angular flux components. Due to the excessive number of tracks in the demanding context of 3D large-scale calculations, reliable acceleration techniques are developed in order to obtain a faster iterative solver, especially for problems with high-scattering ratio. The load balancing strategies include a global round-robin distribution of tracks, an approach where we forecast the calculation load implied by each track length and a macro-band decomposition where tracks crossing the same regions are grouped together. The performance of the PVM and MPI implementations in the characteristics solver is analyzed for realistic applications. (author)