Parallelization of a Monte Carlo ion implantation simulator

We present a parallelization method based on message passing interface (MPI) for a Monte Carlo program for two-dimensional (2-D) and three-dimensional (3-D) simulation of ion implantations. We use a master-slave strategy where the master process synchronizes the slaves and performs the input-output operations, while the slaves perform the physical simulation. For this method the simulation domain is geometrically distributed among several CPU's which have to exchange only very little information during the simulation. Thereby, the communication overhead between the CPU's is kept so low that it has almost no influence on the performance gain even if a standard network of workstations is used instead of a massively parallel computer to perform the simulation. We have optimized the performance gain by identifying bottlenecks of this strategy when it is applied to arbitrary geometries consisting of various materials. This requires the application of different physical models within the simulation domain and makes it impossible to determine a reasonable domain distribution before starting the simulation. Due to a feedback between master and slaves by online performance measurements, we obtain an almost linear performance gain on a cluster of workstations with just slightly varying processor loads. Besides the increase in performance, the parallelization method also achieves a distribution of the required memory. This allows 3-D simulations on a cluster of workstations, where each single machines would not have enough memory to perform the simulation on its own.