Conjunctive Partial Deduction Research Articles

An Empirical Study of Partial Deduction for miniKanren

We study conjunctive partial deduction, an advanced specialization technique aimed at improving the performance of logic programs, in the context of relational programming language miniKanren. We identify a number of issues, caused by miniKanren peculiarities, and describe a novel approach to specialization based on partial deduction and supercompilation. The results of the evaluation demonstrate successful specialization of relational interpreters. Although the project is at an early stage, we consider it as the first step towards an efficient optimization framework for miniKanren.

Transforming Coroutining Logic Programs into Equivalent CHR Programs

We extend a technique called Compiling Control. The technique transforms coroutining logic programs into logic programs that, when executed under the standard left-to-right selection rule (and not using any delay features) have the same computational behavior as the coroutining program. In recent work, we revised Compiling Control and reformulated it as an instance of Abstract Conjunctive Partial Deduction. This work was mostly focused on the program analysis performed in Compiling Control. In the current paper, we focus on the synthesis of the transformed program. Instead of synthesizing a new logic program, we synthesize a CHR(Prolog) program which mimics the coroutining program. The synthesis to CHR yields programs containing only simplification rules, which are particularly amenable to certain static analysis techniques. The programs are also more concise and readable and can be ported to CHR implementations embedded in other languages than Prolog.

Abstract conjunctive partial deduction for the analysis and compilation of coroutines

Abstract We provide an approach to formally analyze the computational behavior of coroutines in logic programs and to compile these computations into new programs, not requiring any support for coroutines. The problem was already studied near to 30 years ago, in an analysis and transformation technique called compiling control. However, this technique had a strong ad hoc flavor: the completeness of the analysis was not well understood and its symbolic evaluation was also rather ad hoc. We show how abstract conjunctive partial deduction, introduced by Leuschel in 2004, provides an appropriate setting to redefine compiling control. We define an abstract domain and all abstract operations required by abstract conjunctive partial deduction. We prove that these concepts satisfy all the correctness conditions imposed by the framework and therefore inherit its main correctness theorem. We also show that there exist more complex coroutining examples which do not fit within abstract conjunctive partial deduction and we propose some further extensions to include them.

A framework for the integration of partial evaluation and abstract interpretation of logic programs

Recently the relationship between abstract interpretation and program specialization has received a lot of scrutiny, and the need has been identified to extend program specialization techniques so as to make use of more refined abstract domains and operators. This article clarifies this relationship in the context of logic programming, by expressing program specialization in terms of abstract interpretation. Based on this, a novel specialization framework, along with generic correctness results for computed answers and finite failure under SLD-resolution, is developed.This framework can be used to extend existing logic program specialization methods, such as partial deduction and conjunctive partial deduction, to make use of more refined abstract domains. It is also shown how this opens up the way for new optimizations. Finally, as shown in the paper, the framework also enables one to prove correctness of new or existing specialization techniques in a simpler manner.The framework has already been applied in the literature to develop and prove correct specialization algorithms using regular types, which in turn have been applied to the verification of infinite state process algebras.

Conjunctive partial deduction: foundations, control, algorithms, and experiments

Partial deduction in the Lloyd–Shepherdson framework cannot achieve certain optimisations which are possible by unfold/fold transformations. We introduce conjunctive partial deduction, an extension of partial deduction accommodating such optimisations, e.g., tupling and deforestation. We first present a framework for conjunctive partial deduction, extending the Lloyd–Shepherdson framework by considering conjunctions of atoms (instead of individual atoms) for specialisation and renaming. Correctness results are given for the framework with respect to computed answer semantics, least Herbrand model semantics, and finite failure semantics. Maintaining the well-known distinction between local and global control, we describe a basic algorithm for conjunctive partial deduction, and refine it into a concrete algorithm for which we prove termination. The problem of finding suitable renamings which remove redundant arguments turns out to be important, so we give an independent technique for this. A fully automatic implementation has been undertaken, which always terminates. Differences between the abstract semantics and Prolog's left-to-right execution motivate deviations from the abstract technique in the actual implementation, which we discuss. The implementation has been tested on an extensive set of benchmarks which demonstrate that conjunctive partial deduction indeed pays off, surpassing conventional partial deduction on a range of small to medium-size programs, while remaining manageable in an automatic and terminating system.