Clock synchronization algorithm for parallel road-traffic simulation system in a wide area

Parallel simulation has contributed to reducing the execution time in simul ating a large complex system. The system is partitioned into N disjoint sub systems, each of which is assigned to one of N processors and the simulatio ns of subsystems are carried out using them in parallel. Parallel simulatio n needs more overhead time for simulation in comparison with a single proce ssor. This is generated to synchronize the simulation clock and to process the communication between N distributed processors. Almost all parallel sim ulations have been conducted on systems which have been represented only th rough the discrete-change model. A few algorithms have been proposed for si mulation using the continuous-change model. However, a universal and effect ive algorithm has not yet been established for parallel simulation with the continuous or the combined model. Thus, we studied an algorithm to synchro nize the simulation clock and a methodology for communication based on road -traffic system simulation with the aim of establishing universal methods. Road-traffic simulation using a microscopic model includes both the discret e-change model and continuous-change model. We propose an algorithm which i s based on the CTW (conservative time window) approach and which predicts t he simulation clock allowing synchronization between a subsystem and the ne ighboring subsystems. This paper describes a new algorithm and a methodolog y to synchronize the simulation clock in parallel. We successfully carried out parallel simulations through our algorithm and methodology, and verifie d their effectiveness. (C) 1999 IMACS/Elsevier Science B.V. All rights rese rved.