Time Warp simulation of timed Petri nets: sensitivity of adaptive methods

The unthrottled optimism underlying the Time Warp (TW) parallel simulation protocol can lead to excessive aggressiveness in memory consumption due to saving state histories, and waste of CPU cycles due to overoptimistically progressing simulations that eventually have to be "rolled back". Furthermore, in TW simulations executing in distributed memory environments, the communication overhead induced by the rollback mechanism can cause pathological overall simulation performance. In this work direct optimism control mechanisms are used to overcome these shortcomings by probabilistically controlling simulation progression based on the forecasted time stamp of forthcoming messages. Several forecast methods are presented and their performance is compared for very large Petri net simulation models executed with the TW protocol on the Meiko CS-2.