The 3 R's of optimizing constraint logic programs

ACM Transactions on Programming Languages and Systems, 1996

This paper presents and illustrates a practical approach to the dataflow analysis of constraint logic programming languages using abstract interpretation. It is first argued that, from the framework point of view, it suffices to propose relatively simple extensions of traditional analysis methods which have already been proved useful and practical and for which efficient fixpoint algorithms exist. This is shown by proposing a simple extension of Bruynooghe's traditional framework which allows it to analyze constraint logic programs. Then, and using this generalized framework, two abstract domains and their required abstract functions are presented: the first abstract domain approximates definiteness information and the second one freeness. Finally, an approach for combining those domains is proposed. The two domains and their combination have been implemented and used in the analysis of CLP() and Prolog-III applications. Results from this implementation showing its performance and accuracy are also presented.

Journal of Logic Programming, 1998

The Constraint Logic Programming (CLP) Scheme was introduced by Jaar and Lassez. The scheme gave a formal framework, based on constraints, for the basic operational, logical and algebraic semantics of an extended class of logic programs. This paper presents for the ®rst time the semantic foundations of CLP in a self-contained and complete package. The main contributions are threefold. First, we extend the original conference paper by presenting de®nitions and basic semantic constructs from ®rst principles, giving new and complete proofs for the main lemmas. Importantly, we clarify which theorems depend on conditions such as solution compactness, satisfaction completeness and independence of constraints. Second, we generalize the original results to allow for incompleteness of the constraint solver. This is important since almost all CLP systems use an incomplete solver. Third, we give conditions on the (possibly incomplete) solver which ensure that the operational semantics is con¯uent, that is, has independence of literal scheduling. Ó 1998 Elsevier Science Inc. All rights reserved.

The Journal of Logic Programming, 1998

The Constraint Logic Programming (CLP) Scheme was introduced by Jaar and Lassez. The scheme gave a formal framework, based on constraints, for the basic operational, logical and algebraic semantics of an extended class of logic programs. This paper presents for the ®rst time the semantic foundations of CLP in a self-contained and complete package. The main contributions are threefold. First, we extend the original conference paper by presenting de®nitions and basic semantic constructs from ®rst principles, giving new and complete proofs for the main lemmas. Importantly, we clarify which theorems depend on conditions such as solution compactness, satisfaction completeness and independence of constraints. Second, we generalize the original results to allow for incompleteness of the constraint solver. This is important since almost all CLP systems use an incomplete solver. Third, we give conditions on the (possibly incomplete) solver which ensure that the operational semantics is con¯uent, that is, has independence of literal scheduling.

KBSDE is a knowledge compiler that usee a classification-based approach to map solution constraints in a taek specification onto particular search algorithm components that will be responsible for satisfying those constraints '-,y., local constraints are incorporated in generat: 14' global constraints are incorporated in either .ba*ters or hillclimbing patchen). Associated with each type of search algorithm component is a subcompiler that specialisea in mapping constraints into components of that type. Each of these subcompilem in turn una e classification-baaed approach, matching a constraint p d to it against one of several schemes, .and applying a compilation technique associated with that schema. While much progene h a occurred in our research since we first laid out our classification-bad a p p r o d [TonSl], we focus in this paper on our reformulation research. Two important reformula. tion issuer that arise out of the choice of a schemabased approach are: Compilobility. Can e constraint that does not directly match any of a particular subcompiler's schemaa be reformulated into one that doea? If the efficiency of the compiled search algorithm depends on the compiler's performance, and the compiler'r perforxnance depends on the form in which the constraint waa expressed, can we find forma for constraints which compile better, or reformulak constraints whose forma c m be recognized as ones that compile poorly? In this paper, we deecribe a set of techniques we are developing for partially addressing these i s 0 EfFciency. sua.

Software: Practice and Experience, 2004

Logic programming requires that the programmer convert a problem into a set of constraints based on predicates. Choosing the predicates and introducing appropriate constraints can be intricate and error-prone. If the problem domain is structured enough, we can let the programmer express the problem in terms of more abstract, higherlevel constraints. A compiler can then convert the higher-level program into a logicprogramming formalism. The compiler writer can experiment with alternative lowlevel representations of the higher-level constraints in order to achieve a high-quality translation. The programmer can then take advantage of both a reduction in complexity and an improvement in runtime speed for all problems within the domain.