Optimizing Compilation of Constraint Handling Rules

Abstract

CHRs are a multi-headed committed choice constraint language, commonly applied for writing incremental constraint solvers. CHRs are usually implemented as a language extension that compiles to the underlying language. In this paper we discuss the optimizing compilation of Constraint Handling Rules (CHRs). In particualr, we show how we can use different kinds of information in the compilation of CHRs in order to obtain access efficiency, and a better translation of the CHR rules into the underlying language. The kinds of information used include the types, modes, determinism, functional dependencies and symmetries of the CHR constraints. We also show how to analyze CHR programs to determine information about functional dependencies, symmetries and other kinds of information supporting optimizations.