Scheduling Time Warp processes using adaptive control techniques

Abstract

Optimistic techniques using the Time Warp mechanism has shown great promise in speeding up parallel discrete event simulations. However, Time Warp has been plagued by problems such as excessive rollbacks, memory usage, and wasted lookahead computation. In particular, excessive rollbacks can result in a deterioration of the advancement of the simulation. Consequently, techniques to properly control the optimism in Time Warp are needed to alleviate nonproductive lookahead. This paper presents a logical process (LP) scheduling algorithm based on concepts from adaptive control theory. In particular, we develop a performance index called 'useful work'. The useful work parameter represents the amount of productive work done by the process and it is used by our scheduling algorithm to aid in LP scheduling decisions. The scheduling algorithm presented in this paper is compared with the widely used 'smallest timestamp first' scheduling algorithm to show its usefulness in a Time Warp simulation.