Fast Simulation of Open Queueing Systems

We describe a technique developed by the authors for fast simulation of open queueing networks. The technique takes advantage of the recursive nature of departure times of customers in various parts of the system. The event calendar is circumvented using these recursive relationships whenever possible. A framework for identifying these recursive aspects of a network is presented. The technique involves identifying the servers in the system at which flows merge or diverge. Knowledge about the merge and diverge points defines the dependency relationships a specific customer has with other customers at each point in the system. The concept of a system level is based on these dependency relationships. The technique is implemented in the object oriented language SmallTalk 80. The implementation utilizes Windows interfaces and allows graphical analysis of the simulation results. The implementation is shown to achieve significant reductions in execution time compared with the traditional discrete-event approach to simulation of such networks in most cases. Several different types of systems are explored in an attempt to characterize those systems on which the technique functions well