Efficient Analysis of Simultaneous Events in Distributed Simulation

Simultaneous events are a fundamental challenge in distributed discrete-event simulation: Different execution orders may lead to different simulation results. Commonly, simultaneous events are handled by tie-breaking rules in order to guarantee reproducibility. A second approach, however, is examining different execution orders with a branching mechanism. By analyzing the effects of simultaneous events, confidence in simulation results may be increased. Naturally, branching may get expensive with large numbers of simultaneous events. Thus, efficiency is crucial for branching in order to be a practical method. In this paper, we present an efficient branching mechanism for simultaneous events in distributed simulation, which may be used in conjunction with, or as an alternative to tie-breaking rules. We apply techniques which optimize the detection of simultaneous events and reduce the number of branches as much as possible. Furthermore, we use cloning to share computations among different branches.