Rollback Overhead Reduction Methods for Time Warp Distributed Simulation

Parallel discrete event simulation is a useful technique to improve performance of sequential discrete event simulation. We consider the Time Warp algorithm for asynchronous distributed discrete event simulation. Time Warp is an optimistic synchronization mechanism for asynchronous distributed systems that allows a system to violate the synchronisation constraint and, in this case, make the system to rollback to a correct state. We focus on the kernel of the Time Warp algorithm, that is the rollback operation and we propose some techniques to reduce the overhead due to this operation. In particular we propose a method to reduce the overhead involved in state saving operation, two methods to reduce the overhead of a single rollback operation and a method to reduce the overall number of rollbacks. These methods have been implemented in a distributed simulation environment on a distributed memory system. Some experimental results show the effectiveness of the proposed techniques.