Time Warp simulation in time constrained systems

Abstract

The suitability of the Time Warp mechanism to perform simulations with real-time constraints is examined. A model for Time Warp is developed that accounts for overheads such as state saving, state restoration, and sending and transmitting positive and negative messages. A criterion called R-schedulability is defined to indicate whether or not computations can meet real-time deadlines. It is shown that if false events (events that will be rolled back or cancelled later) are generated, and there are no committed events with timestamps equal to those of the false events, Time Warp cannot meet the R-schedulability criterion. Further, if aggressive cancellation is used, scheduling guarantees still cannot be made even in the absence of such false events. However, Time Warp using lazy cancellation is shown to be R-schedulable provided such false events do not exist. Finally, based on these results, bounds on the execution time of a Time Warp simulation are derived.