Retroactive Subsumption-Based Tabled Evaluation of Logic Programs

Cruz, Flavio; Rocha, Ricardo

doi:10.1007/978-3-642-15675-5_13

Cited by 4 publications

(5 citation statements)

References 5 publications

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“…Experiments using the YapTab tabling engine with support for RCS showed very good results when compared to nonretroactive call by subsumption (Cruz and Rocha 2010). Here, we focus on the retrieval algorithm and for this we analyze experimental results using some well-known tabled programs.…”

Section: Resultsmentioning

confidence: 99%

“…In order to solve this problem, we implemented an extension to the original TST design, called Retroactive Call Subsumption (RCS) (Cruz and Rocha 2010), that supports subsumption-based tabling by allowing full sharing of answers between subsumptive subgoals, independently of the order they are called. RCS works by selectively pruning the evaluation of subsumed subgoals when a more general subgoal appears later on.…”

Section: Introductionmentioning

confidence: 99%

“…RCS works by selectively pruning the evaluation of subsumed subgoals when a more general subgoal appears later on. We designed a new table space organization, called Single Time-Stamped Trie (STST) (Cruz and Rocha 2010) where answers are represented only once. We also designed a new algorithm to efficiently retrieve the set of currently evaluating subgoals that are subsumed by (instances of) a more general subgoal.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Efficient instance retrieval of subgoals for subsumptive tabled evaluation of logic programs

Cruz¹,

Rocha²

2011

Theory and Practice of Logic Programming

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Tabled evaluation is an implementation technique that solves some problems of traditional Prolog systems in dealing with recursion and redundant computations. Most tabling engines determine if a tabled subgoal will produce or consume answers by using variant checks. A more refined method, named call subsumption, considers that a subgoal A will consume from a subgoal B if A is subsumed by (an instance of) B, thus allowing greater answer reuse. We recently developed an extension, called Retroactive Call Subsumption, that improves upon call subsumption by supporting bidirectional sharing of answers between subsumed/subsuming subgoals. In this paper, we present both an algorithm and an extension to the table space data structures to efficiently implement instance retrieval of subgoals for subsumptive tabled evaluation of logic programs. Experiments results using the YapTab tabling system show that our implementation performs quite well on some complex benchmarks and is robust enough to handle a large number of subgoals without performance degradation.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Efficient instance retrieval of subgoals for subsumptive tabled evaluation of logic programs

Cruz¹,

Rocha²

2011

Theory and Practice of Logic Programming

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“…However, the mechanisms to efficiently support subsumption-based tabling are harder to implement, which makes subsumption-based tabling not as popular as variant-based tabling. The Yap Prolog system implements both approaches for sequential tabling (Cruz and Rocha 2010;Santos Costa et al 2012), but for concurrent tabled evaluation, Yap follows the variant-based tabling approach.…”

Section: Table Space Organizationmentioning

confidence: 99%

Table space designs for implicit and explicit concurrent tabled evaluation

Areias¹,

Rocha²

2018

Theory and Practice of Logic Programming

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One of the main advantages of Prolog is its potential for the implicit exploitation of parallelism and, as a high-level language, Prolog is also often used as a means to explicitly control concurrent tasks. Tabling is a powerful implementation technique that overcomes some limitations of traditional Prolog systems in dealing with recursion and redundant subcomputations. Given these advantages, the question that arises is if tabling has also the potential for the exploitation of concurrency/parallelism. On one hand, tabling still exploits a search space as traditional Prolog but, on the other hand, the concurrent model of tabling is necessarily far more complex, since it also introduces concurrency on the access to the tables. In this paper, we summarize Yap's main contributions to concurrent tabled evaluation and we describe the design and implementation challenges of several alternative table space designs for implicit and explicit concurrent tabled evaluation that represent different tradeoffs between concurrency and memory usage. We also motivate for the advantages of using fixed-size and lock-free data structures, elaborate on the key role that the engine's memory allocator plays on such environments, and discuss how Yap's mode-directed tabling support can be extended to concurrent evaluation. Finally, we present our future perspectives toward an efficient and novel concurrent framework which integrates both implicit and explicit concurrent tabled evaluation in a single Prolog engine.

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“…CS p can be made the active store (which in some cases can speed up the execution of the generator -see Section 3.4), in which case CS o is returned to be used by solver recover CS/1 to reinstall it in order to continue the execution. P G may be unified with a list of existing generators entailed by the new tabled call (whose constraint stores would be removed from Call S ), which can be pruned and transformed into consumers of the new tabled call by prune generators/1, similarly to retroactive subsumption tabling [19].…”

Section: Tclp Program Transformationmentioning

confidence: 99%

A General Implementation Framework for Tabled CLP

Guzmán

Carro

Hermenegildo

et al. 2012

Functional and Logic Programming

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Abstract. This paper describes a framework to combine tabling evaluation and constraint logic programming (TCLP). While this combination has been studied previously from a theoretical point of view and some implementations exist, they either suffer from a lack of efficiency, flexibility, or generality, or have inherent limitations with respect to the programs they can execute to completion (either with success or failure). Our framework addresses these issues directly, including the ability to check for answer / call entailment, which allows it to terminate in more cases than other approaches. The proposed framework is experimentally compared with existing solutions in order to provide evidence of the mentioned advantages.

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Retroactive Subsumption-Based Tabled Evaluation of Logic Programs

Cited by 4 publications

References 5 publications

Efficient instance retrieval of subgoals for subsumptive tabled evaluation of logic programs

Efficient instance retrieval of subgoals for subsumptive tabled evaluation of logic programs

Table space designs for implicit and explicit concurrent tabled evaluation

A General Implementation Framework for Tabled CLP

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