Automated Analysis of Concurrent Systems with the Constrained Expression Toolset

Reviewer: Jorgen Staunstrup

Constrained expressions can be used to model collections of asynchronous processes. This paper is an overview of the technique and a set of tools supporting it. A concurrent computation can be modeled as a set of traces. This set can be specified either by explicitly showing how to generate it or by implicitly stating constraints it must satisfy. Both approaches have been tried in the past. This work uses the latter approach, based on a notation called constrained expression design language (CEDL). Other authors have discussed a similar concept called “path expressions.” The paper describes a number of tools that can be used to analyze constrained expressions. A fundamental part of these tools is a standard package (called MINOS) for solving linear inequalities. The tools have been used on a number of toy examples discussed in the literature on concurrent computing (dining philosophers, gas station, readers and writers, and distributed mutual exclusion). The authors show how the tools can be used to demonstrate the absence or presence of deadlock. In some cases, it is possible to handle hundreds of processes. Running time and experience from a number of such experiments are reported and compared to the results obtained by using other tools. The paper should interest anyone working with tools supporting concurrent computing.