CLUSTERED SIMULATION EXPERIMENTER: A tool for concurrent simulation execution on loosely coupled workstations

The "Clustered Simulation Experimenter" (CSX) project intends to make massive concurrent experiments without having to be concerned in locating computational resources to carry it out. This paper presents a tool whose principal purpose is to use a lot of idle and heterogeneous workstations at university laboratories and research centers to run concurrent simulations. The approach consists of adding and eliminating machines, with different architectures and operating systems, to a heterogeneous and dynamic cluster that permits to execute a distributed application. The communication among the machines and the co-ordination of the distributed application processes uses a typical network infrastructure using PVM v3.4. (Parallel Virtual Machine). An asynchronous design of the communications lets to execute sequential simulation models as fast as running it as normal simulation programs. Simulations executed using CSX are classic discrete-event oriented models that, basically, will be run using replication techniques, and monitored for extracting statistic information of the output variables of the model, letting CSX to improve response times through possibilities of an improved statistic output analysis. The first effort has been to be able to monitor the output variables of the models without causing an excessive "overhead". We present here how has been applied to SMPL, but the purpose is to use it in simulators such as CSIM, SIM++, QNAP and DEVS*. Due to the fact that the distributed execution environment is highly variable and is shared with other users, it is necessary to apply dynamic load balancing techniques.