GMSim: a tool for compositional GSMP modeling

The development of a discrete-event simulation tool, called GMSim, based on the generalized semi-Markov process (GSMP) formalism is described. The GSMP representation comprises both analysis and simulation in a unified framework. This paper focuses on the simulation aspect and how to deal with a combinatorially exploding state space. A compositional GSMP modeling methodology is proposed, which in turn is combined with an object-oriented programming approach. A key feature of the resulting tool is the close resemblance with the underlying mathematical structure. This facilitates coherent modeling and also an efficient implementation. The tool is completely generic and extendible by Tcl script programming. Application specific components are developed by C++ programming in combination with M4 macro processing.