Performance of a riskfree Time Warp operating system

Abstract

Optimistic methods of synchronizing parallel discrete event simulations can be risky by sending (positive) messages (events) before they have been committed. Risky methods often use anti-messages (negative messages) to cancel incorrectly sent positive messages. Riskfree methods are more conservative, they do not send messages until they are known to be correct. The Time Warp Operating System (TWOS) uses anti-messages. Riskfree TWOS is implemented and tested on the standard TWOS benchmarks. Performance of the riskfree TWOS is dependent on the amount of lookahead in the simulation. Good lookahead was required for even reasonable performance. Tracker, a simulation of the riskfree simulation, is used to give idealized best case riskfree performance. BeRisky is an example simulation which has a speedup of n for Time Warp, but only a speedup of 2 for riskfree methods.