In the area of discrete event simulation (DES), event simultaneity occurs when any two events are scheduled to happen at the same point in simulated time. Simulation determinism is the expectation that the same semantically configured simulation will be guaranteed to repeatedly reproduce identical results. Since events in DES are the sole mechanism for state change, ensuring consistent real-time event processing order is crucial to maintaining determinism. This is synonymous with finding a consistent total ordering of events. In this work, we extend the concept of virtual time to utilize an arbitrary-length series of tie-breaking values to preserve determinism in parallel, optimistically executed simulations without imposing additional bias influencing the ordering of otherwise incomparable events. Furthermore, by changing the core pseudo-random number generator seed at initialization, different orderings of events incomparable by standard virtual time can be observed, allowing for fair probing of other potential simulation outcomes. We implement and evaluate this extended definition of virtual time in the Rensselaer Optimistic Simulation System (ROSS) with three simulation models and discuss the importance of deterministic event ordering given the existence of event ties.
翻译:在离散事件模拟(DES)领域,当两个事件都计划在模拟时间的同一点同时发生时,即发生事件同时发生。模拟确定性是预期同样的语义配置模拟将保证重复重复相同的结果。由于DES的事件是国家变化的唯一机制,确保连续实时事件处理秩序对于维持确定性至关重要。这与寻找一致的整体事件顺序是同义的。在这项工作中,我们扩大了虚拟时间的概念,利用任意的断线值系列来同时保存确定性,乐观地执行的模拟,而不施加额外的偏差来影响本来无法比较的事件的顺序。此外,通过在初始化时改变核心的伪随机数生成器种子,可以观察到与标准虚拟时间相容的不同事件顺序,从而可以公平地预测其他可能的模拟结果。我们用三个模拟模型来实施和评估Rensselaer Oppimic Simmic Systemulation系统(RSOS)的这一扩大的虚拟时间定义,并讨论确定性事件秩序的重要性。