Redundant Argument Filtering of Logic Programs

This paper is concerned with the problem of removing, from a given logic program, redundant arguments. These are arguments which can be removed without affecting correctness. Most program specialisation techniques, even through they perform argument filtering and redundant clause removal, fail to remove a substantial number of redundant arguments, yielding in some cases rather inefficient residual programs. We formalise the notion of a redundant argument and show that one cannot decide effectively whether a given argument is redundant. We then give a safe, effective approximation of the notion of a redundant argument and describe several simple and efficient algorithms calculating based on the approximation notion. Redundant Argument Filtering of Logic Programs Michael Leuschel1 & Morten Heine S rensen2 1 Department of Computer Science, Katholieke Universiteit Leuven, Celestijnenlaan 200A, B-3001, Heverlee, Belgium, [email protected]. 2 Department of Computer Science, University of Copenhagen, Universitetsparken 1, DK-2100 Copenhagen, Denmark. [email protected]. Abstract. This paper is concerned with the problem of removing, from a given logic program, redundant arguments. These are arguments which can be removed without a ecting correctness. Most program specialisation techniques, even though they perform argument ltering and redundant clause removal, fail to remove a substantial number of redundant arguments, yielding in some cases rather ine cient residual programs. We formalise the notion of a redundant argument and show that one cannot decide e ectively whether a given argument is redundant. We then give a safe, e ective approximation of the notion of a redundant argument and describe several simple and e cient algorithms calculating based on the approximative notion. We conduct extensive experiments with our algorithms on mechanically generated programs illustrating the practical bene ts of our approach.