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Logic program specialisation through partial deduction: Control issues
 THEORY AND PRACTICE OF LOGIC PROGRAMMING
, 2002
"... Program specialisation aims at improving the overall performance of programs by performing source to source transformations. A common approach within functional and logic programming, known respectively as partial evaluation and partial deduction, is to exploit partial knowledge about the input. It ..."
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Cited by 66 (13 self)
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Program specialisation aims at improving the overall performance of programs by performing source to source transformations. A common approach within functional and logic programming, known respectively as partial evaluation and partial deduction, is to exploit partial knowledge about the input. It is achieved through a wellautomated application of parts of the BurstallDarlington unfold/fold transformation framework. The main challenge in developing systems is to design automatic control that ensures correctness, efficiency, and termination. This survey and tutorial presents the main developments in controlling partial deduction over the past 10 years and analyses their respective merits and shortcomings. It ends with an assessment of current achievements and sketches some remaining research challenges.
Ensuring Global Termination of Partial Deduction while Allowing Flexible Polyvariance
, 1995
"... The control of polyvariance is a key issue in partial deduction of logic programs. Certainly, only finitely many specialised versions of any procedure should be generated, while, on the other hand, overly severe limitations should not be imposed. In this paper, wellfounded orderings serve as a star ..."
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Cited by 66 (17 self)
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The control of polyvariance is a key issue in partial deduction of logic programs. Certainly, only finitely many specialised versions of any procedure should be generated, while, on the other hand, overly severe limitations should not be imposed. In this paper, wellfounded orderings serve as a starting point for tackling this socalled "global termination" problem. Polyvariance is determined by the set of distinct "partially deduced" atoms generated during partial deduction. Avoiding adhoc techniques, we formulate a quite general framework where this set is represented as a tree structure. Associating weights with nodes, we define a wellfounded order among such structures, thus obtaining a foundation for certified global termination of partial deduction. We include an algorithm template, concrete instances of which can be used in actual implementations, prove termination and correctness, and report on the results of some experiments. Finally, we conjecture that the proposed framewor...
Controlling generalisation and polyvariance in partial deduction of normal logic programs
, 1996
"... In this paper, we further elaborate global control for partial deduction: For which atoms, among possibly innitely many, should partial deductions be produced, meanwhile guaranteeing correctness as well as termination, and providing ample opportunities for negrained polyvariance? Our solution is b ..."
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Cited by 60 (40 self)
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In this paper, we further elaborate global control for partial deduction: For which atoms, among possibly innitely many, should partial deductions be produced, meanwhile guaranteeing correctness as well as termination, and providing ample opportunities for negrained polyvariance? Our solution is based on two ingredients. First, we use the wellknown concept of a characteristic tree to guide abstraction (or generalisation) and polyvariance, and aim for producing one specialised procedure per characteristic tree generated. Previous work along this line failed to provide abstraction correctly dealing with characteristic trees. We show how this can be rectied in an elegant way. Secondly, we structure combinations of atoms and associated characteristic trees in global trees registering \causal " relationships among such pairs. This will allow us to spot looming nontermination and consequently perform proper generalisation in order to avert the danger, without having to impose a depth bound on characteristic trees. Leaving unspecied the specic local control one may wish to plug in, the resulting global control strategy enables partial deduction that always terminates in an elegant, non ad hoc way, while providing excellent specialisation as well as negrained (but reasonable) polyvariance.
Global control for partial deduction through characteristic atoms and global trees
, 1995
"... Abstract. Recently, considerable advances have been made in the (online) control of logic program specialisation. A clear conceptual distinction has been established between local and global control and on both levels concrete strategies as well as general frameworks have been proposed. For global c ..."
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Cited by 49 (22 self)
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Abstract. Recently, considerable advances have been made in the (online) control of logic program specialisation. A clear conceptual distinction has been established between local and global control and on both levels concrete strategies as well as general frameworks have been proposed. For global control in particular, recent work has developed concrete techniques based on the preservation of characteristic trees (limited, however, by a given, arbitrary depth bound) to obtain a very precise control of polyvariance. On the other hand, the concept of an mtree has been introduced as a refined way to trace “relationships ” of partially deduced atoms, thus serving as the basis for a general framework within which global termination of partial deduction can be ensured in a non ad hoc way. Blending both, formerly separate, contributions, in this paper, we present an elegant and sophisticated technique to globally control partial deduction of normal logic programs. Leaving unspecified the specific local control one may wish to plug in, we develop a concrete global control strategy combining the use of characteristic atoms and trees with global (m)trees. We thus obtain partial deduction that always terminates in an elegant, non ad hoc way, while providing excellent specialisation as well as finegrained (but reasonable) polyvariance. We conjecture that a similar approach may contribute to improve upon current (online) control strategies for functional program transformation methods such as (positive) supercompilation. 1
Homeomorphic embedding for online termination of symbolic methods
 In The essence of computation, volume 2566 of LNCS
, 2002
"... Abstract. Wellquasi orders in general, and homeomorphic embedding in particular, have gained popularity to ensure the termination of techniques for program analysis, specialisation, transformation, and verification. In this paper we survey and discuss this use of homeomorphic embedding and clarify ..."
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Cited by 43 (7 self)
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Abstract. Wellquasi orders in general, and homeomorphic embedding in particular, have gained popularity to ensure the termination of techniques for program analysis, specialisation, transformation, and verification. In this paper we survey and discuss this use of homeomorphic embedding and clarify the advantages of such an approach over one using wellfounded orders. We also discuss various extensions of the homeomorphic embedding relation. We conclude with a study of homeomorphic embedding in the context of metaprogramming, presenting some new (positive and negative) results and open problems.
Transformation of Logic Programs
 Handbook of Logic in Artificial Intelligence and Logic Programming
, 1998
"... Program transformation is a methodology for deriving correct and efficient programs from specifications. In this chapter, we will look at the so called 'rules + strategies' approach, and we will report on the main techniques which have been introduced in the literature for that approach, i ..."
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Cited by 40 (4 self)
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Program transformation is a methodology for deriving correct and efficient programs from specifications. In this chapter, we will look at the so called 'rules + strategies' approach, and we will report on the main techniques which have been introduced in the literature for that approach, in the case of logic programs. We will also present some examples of program transformation, and we hope that through those examples the reader may acquire some familiarity with the techniques we will describe.
Ecological Partial Deduction: Preserving Characteristic Trees Without Constraints
 Logic Program Synthesis and Transformation. Proceedings of LOPSTR'95, LNCS 1048
, 1995
"... . A partial deduction strategy for logic programs usually uses an abstraction operation to guarantee the finiteness of the set of atoms for which partial deductions are produced. Finding an abstraction operation which guarantees finiteness and does not loose relevant information is a difficult probl ..."
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Cited by 26 (16 self)
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. A partial deduction strategy for logic programs usually uses an abstraction operation to guarantee the finiteness of the set of atoms for which partial deductions are produced. Finding an abstraction operation which guarantees finiteness and does not loose relevant information is a difficult problem. In earlier work Gallagher and Bruynooghe proposed to base the abstraction operation on characteristic paths and trees. A characteristic tree captures the relevant structure of the generated partial SLDNFtree for a given goal. Unfortunately the abstraction operations proposed in the earlier work do not always produce more general atoms and do not always preserve the characteristic trees. This problem has been solved for purely determinate unfolding rules and definite programs in [12, 13] by using constraints inside the partial deduction process. In this paper we propose an alternate solution which achieves the preservation of characteristic trees for any unfolding rule, normal logic prog...
Constrained Partial Deduction and the Preservation of Characteristic Trees
 NEW GENERATION COMPUTING
, 1997
"... Partial deduction strategies for logic programs often use an abstraction operator to guarantee the finiteness of the set of goals for which partial deductions are produced. Finding an abstraction operator which guarantees finiteness and does not lose relevant information is a difficult problem. I ..."
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Cited by 21 (16 self)
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Partial deduction strategies for logic programs often use an abstraction operator to guarantee the finiteness of the set of goals for which partial deductions are produced. Finding an abstraction operator which guarantees finiteness and does not lose relevant information is a difficult problem. In earlier work Gallagher and Bruynooghe proposed to base the abstraction operator on characteristic paths and trees, which capture the structure of the generated incomplete SLDNFtree for a given goal. In this paper we exhibit the advantages of characteristic trees over purely syntactical measures: if characteristic trees can be preserved upon generalisation, then we obtain an almost perfect abstraction operator, providing just enough polyvariance to avoid any loss of local specialisation. Unfortunately, the abstraction operators proposed in earlier work do not always preserve the characteristic trees upon generalisation. We show that this can lead to important specialisation losses as well as to nontermination of the partial deduction algorithm. Furthermore, this problem cannot be adequately solved in the ordinary partial deduction setting. We therefore extend the expressivity and precision of the Lloyd and Shepherdson partial deduction framework by integrating constraints. We provide formal correctness results for the so obtained generic framework of constrained partial deduction. Within this new framework we are, among others, able to overcome the above mentioned problems by introducing an alternative abstraction operator, based on so called pruning constraints. We thus present a terminating partial deduction strategy which, for purely determinate unfolding rules, induces no loss of local specialisation due to the abstraction while ensuring correctness o...