The effect of time-advance mechanism in modeling and simulation

Abstract

As the discipline of Modeling and Simulation (MandS) becomes more complex, modelers are faced with mounting challenges to design and analyze simulations that effectively address difficult problems across military, industrial, and societal fields. Understanding the effects of time-advance mechanisms (TAMs) is essential to making advances in the design and use of MandS across a wide variety of domains. We perform a series of empirical studies to characterize and compare the influence of discrete event simulation (DES) and discrete time simulation (DTS) approaches, and describe the effects of changes in time "step" sizes across a number of vital simulation areas including queuing systems, combat systems, and human behavior representations of military significance. Our results illustrate that the choice of TAM can have a significant impact on the behavior of models, the output obtained from simulation tools, and the recommendations that are likely to result. We describe inconsistencies and the emergence of unintended behaviors resulting from the use of different TAM approaches and DTS time "steps." We conclude that the DES approach is more likely to produce trustworthy simulation results for decision-making applications, and that the time step approach carries additional inherent risks that are often invisible to modelers of complex systems.