Reduction of Inter-process Communication in Distributed Simulation of Road Traffic

A detailed computer simulation is an important tool for the managing of road traffic. Since it can be very time consuming, it is often performed in a distributed computing environment. The simulated road traffic network is then divided into sub-networks simulated by processes on the nodes of the distributed computer. The inter-process communication necessary for the vehicle transfer and the synchronization can then significantly influence the performance of the distributed road traffic simulation. In this paper, two efficient communication protocols for distributed road traffic simulation, which we developed during our previous research, are compared. These protocols - the Long Step (LS) protocol and the Long Step Binary (LSB) protocol - reduce the inter-process communication using an aggregate message transfer and/or a lossy data compression. Semi-centralized, centralized, and distributed variants of both protocols were thoroughly tested and compared to a reference communication protocol representing a common protocol of distributed road traffic simulators. The tests indicate significant savings of the number of transferred messages and, more importantly, of the total computation time.