On extending more parallelism to serial simulators

The Utilitarian Parallel Simulator (U.P.S.) extends parallelism to the CSIM sequential simulation tool by providing several new modeling constructs. Using conservative synchronization techniques, these constructs automatically support time-synchronized communications between CSIM submodels running on different processors. This paper describes extensions to U.P.S. that allow the user to assist U.P.S. by providing additional 'process lookahead,' thereby reducing the frequency of synchronizations. The use and effect on performance of process lookahead is described for several models. In a mobile cellular communications model, the use of process lookahead results in up to a 60% improvement in speedup on 32 nodes of the IBM SP2. A factor of 3 improvement is obtained on a closed queueing network simulation running on 32 nodes of the Intel Paragon.