A parallel processing system for computing particle interactions includes a plurality of computation nodes arranged according to a geometric partitioning of a simulation volume. Each computation node has storage for particle data. This particle data is associated with particles in a region of the geometrically partitioned simulation volume. The parallel processing system also includes a communication system having links interconnecting the computation nodes. Each of the computation nodes includes a processor subsystem. These processor subsystems cooperate to coordinate computation of the particle interactions in a distributed manner.