Proper parallel Monte Carlo for computed tomography of volcanoes

Most Monte Carlo simulations can be parallelized, or at least easily distributed. However, the parallelization of such programs is not mainstream. In this paper, we propose good practices to distribute a Monte Carlo simulation for computed tomography. We apply this to large edifices (such as volcanoes or pyramids) and give a particular focus on performances. The work included first the optimization of an existing sequential prototype and second the use of reliable parallel random streams. The optimized parallel version runs on a Symmetric Multi-Processor (SMP) and shows a fine and scalable speedup. The cumulated optimizations (sequential and parallel) enabled a speedup of 400X on a 32 cores SMP.