4,103 research outputs found

    Towards a Complete Scheme for Tabled Execution Based on Program Transformation

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    The advantages of tabled evaluation regarding program termination and reduction of complexity are well known —as are the significant implementation, portability, and maintenance efforts that some proposals (especially those based on suspension) require. This implementation effort is reduced by program transformation-based continuation call techniques, at some efficiency cost. However, the traditional formulation of this proposal [1] limits the interleaving of tabled and non-tabled predicates and thus cannot be used as-is for arbitrary programs. In this paper we present a complete translation for the continuation call technique which, while requiring the same runtime support as the traditional approach, solves these problems and makes it possible to execute arbitrary tabled programs. We also present performance results which show that the resulting CCall approach offers a useful tradeoff that can be competitive with other state-of-the-art implementation

    Automatic Generation of CHR Constraint Solvers

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    In this paper, we present a framework for automatic generation of CHR solvers given the logical specification of the constraints. This approach takes advantage of the power of tabled resolution for constraint logic programming, in order to check the validity of the rules. Compared to previous works where different methods for automatic generation of constraint solvers have been proposed, our approach enables the generation of more expressive rules (even recursive and splitting rules) that can be used directly as CHR solvers.Comment: to be published in Theory and Practice of Logic Programming, 16 pages, 2 figure

    Towards flexible goal-oriented logic programming

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    On Combining Linear-Based Strategies for Tabled Evaluation of Logic Programs

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    Tabled evaluation is a recognized and powerful technique that overcomes some limitations of traditional Prolog systems in dealing with recursion and redundant sub-computations. We can distinguish two main categories of tabling mechanisms: suspension-based tabling and linear tabling. While suspension-based mechanisms are considered to obtain better results in general, they have more memory space requirements and are more complex and harder to implement than linear tabling mechanisms. Arguably, the SLDT and DRA strategies are the two most successful extensions to standard linear tabled evaluation. In this work, we propose a new strategy, named DRS, and we present a framework, on top of the Yap system, that supports the combination of all these three strategies. Our implementation shares the underlying execution environment and most of the data structures used to implement tabling in Yap. We thus argue that all these common features allows us to make a first and fair comparison between these different linear tabling strategies and, therefore, better understand the advantages and weaknesses of each, when used solely or combined with the others.Comment: 16 pages, 9 figures, International Conference on Logic Programming (ICLP 2011

    A Polyvariant Binding-Time Analysis for Off-line Partial Deduction

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    We study the notion of binding-time analysis for logic programs. We formalise the unfolding aspect of an on-line partial deduction system as a Prolog program. Using abstract interpretation, we collect information about the run-time behaviour of the program. We use this information to make the control decisions about the unfolding at analysis time and to turn the on-line system into an off-line system. We report on some initial experiments.Comment: 19 pages (including appendix) Paper (without appendix) appeared in Programming Languages and Systems, Proceedings of the European Symposium on Programming (ESOP'98), Part of ETAPS'98 (Chris Hankin, eds.), LNCS, vol. 1381, 1998, pp. 27-4
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