EVALUATION OF THE DOMAIN PROP

The domain Prop [11, 30] is a conceptually simple and elegant abstract domain to compute groundness information for Prolog programs, where abstract substitutions are represented by Boolean functions. Prop has raised much theoretical interest recently, but little is known about the practical accuracy and efficiency of this domain. Experimental evaluation of Prop is particularly important since Prop theoretically needs to solve a co-NP-Complete problem. However, this complexity issue may not matter much in practice because the size of the abstract substitutions is bounded since Prop would only work on the clause variables in many frameworks. The purpose of this paper is to study the performance of domain Prop. Its first contribution is to describe an implementation of the domain Prop and to use it to instantiate a generic abstract interpretation algorithm [17, 23, 27]. A key feature of the implementation is the use of ordered binary decision graphs to provide a compact representation of many Boolean functions. Its second contribution is to describe the design and implementation of a new domain, Pat(Prop), combining the domain Prop with structural information about the subterms. This new domain may significantly improve the accuracy of the domain Prop on programs manipulating difference-lists. Both implementations (resp. 6000 and 12,000 lines of C) have been evaluated systematically, and their efficiency and accuracy for groundness inference have been compared with several other abstract domains. The interest of Pat(Prop) and Prop for on-line analysis is also investigated.