Repeated Redundant Inequalities in Constraint Logic Programming

Abstract

Future redundant inequalities in a constraint logic program are those that are guaranteed to be subsumed after no more than one subsequent procedure call, whenever they are encountered at run time. It has been noted that such inequalities need only be tested for consistency with the current constraint set, thus resulting in dramatic savings in execution speed and space usage. Furthermore, they can be detected at compile time, leading to a valuable compiler optimization. By considering the role of such inequalities in a program, we generalize the notion of future redundancy in a number of ways and thus broaden its applicability. As a result, we show how to dramatically improve the performance of a wider class of programs that rely heavily on inequalities.