pGVT: an algorithm for accurate GVT estimation

The time warp mechanism uses memory space to save event and state information for rollback processing. As the simulation advances in time, old state and event information can be discarded and the memory space reclaimed. This reclamation process is called fossil collection and is guided by a global time value called Global Virtual Time (GVT). That is, GVT represents the greatest minimum time of the fully committed events (the time before which no rollback will occur). GVT is then used to establish a boundary for fossil collection. This paper presents a new algorithm for GVT estimation called pGVT. pGVT was designed to support accurate estimates of the actual GVT value and it operates in an environment where the communication subsystem does not support FIFO message delivery and where message delivery failure may occur. We show that pGVT correctly estimates GVT values and present some performance comparisons with other GVT algorithms.