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

Parallel simulation has contributed to reducing the execution time in simulating a large complex system. The system is partitioned into N disjoint subsystems, each of which is assigned to one of N processors and the simulations of subsystems are carried out using them in parallel. Parallel simulation needs more overhead time for simulation in comparison with a single processor. This is generated to synchronize the simulation clock and to process the communication between N distributed processors. Almost all parallel simulations have been conducted on systems which have been represented only through the discrete-change model. A few algorithms have been proposed for simulation using the continuous-change model. However, a universal and effective algorithm has not yet been established for parallel simulation with the continuous or the combined model. Thus, we studied an algorithm to synchronize 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 discrete-change model and continuous-change model. We propose an algorithm which is based on the CTW (conservative time window) approach and which predicts the simulation clock allowing synchronization between a subsystem and the neighboring subsystems. This paper describes a new algorithm and a methodology to synchronize the simulation clock in parallel. We successfully carried out parallel simulations through our algorithm and methodology, and verified their effectiveness.