Trees and Butterflies Barriers in Distributed Simulation System: A Better Approach to Improve Latency and the Processor Idle Time

Global virtual time (GVT) is used in parallel discrete event simulations to reclaim memory, commit output, detect termination, and handle errors. Mattern 's [I] has proposed G VT approximation with distributed termination detection algorithm. This algorithm works fine and gives optimal performance in terms of accurate GVT computation at the expense of slower execution rate. This slower execution rate results a high GVT latency. Due to the high GVT latency, the processors involve in communication remain idle during that period of time. As a result, the overall throughput of a discrete event parallel simulation system degrades significantly. Thus, the high G VT latency prevents the widespread use of this algorithm in discrete event parallel simulation system. However, if we could improve the latency of GVT computation, most of the discrete event parallel simulation system would likely take advantage of this technique in terms of accurate G VT computation. In this paper, we examine the potential use of tress and butterflies barriers with the Mattern's GVT structure using a ring. Simulation results demonstrate that the use of tree barriers with the Mattern's GVT structure can significantly improve the latency time and thus increase the overall throughput of the parallel simulation system. The performance measure adopted in this paper is the achievable latency for a fixed number of processors and the number of message transmission during the G VT computation.