Critical path analysis of concurrent Ada programs using colored Petri nets: rewrite rules

Abstract

The authors use a colored Petri net model of a substantial subset of Ada to do critical path analysis. They are primarily interested in determining the circumstances under which a concurrent program will take the most time. This is done by finding the critical path. The authors associate with each transition a cost representing the time necessary to execute the corresponding instruction. They define the critical path as a generalization of the usual PERT notion. The critical path in a colored Petri net takes into account the special semantics of firing only enabled transitions. The authors do not modify the semantics to take into account time as in various models of Petri nets with time. They do critical path analysis by transforming the net to an equivalent net whose critical path takes the same amount of time. The Petri net is rewritten over and over again until the net is reduced to a single transition. >