Novel Models for Or-Parallel Logic Programs: A Performance Analysis

Costa, Vítor Santos; Rocha, Ricardo; Silva, Fernando M. A.

doi:10.1007/3-540-44520-x_102

Cited by 3 publications

(1 citation statement)

References 8 publications

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“…2. Because workers see a contiguous stack, copying imposes less overheads on the engine and has high performance compared to the other approaches (Santos Costa et al 2000). 3.…”

Section: Memory Modelmentioning

confidence: 99%

Threads and or-parallelism unified

Costa¹,

Dutra²,

Rocha³

2010

Theory and Practice of Logic Programming

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One of the main advantages of Logic Programming (LP) is that it provides an excellent framework for the parallel execution of programs. In this work we investigate novel techniques to efficiently exploit parallelism from real-world applications in low cost multi-core architectures. To achieve these goals, we revive and redesign the YapOr system to exploit or-parallelism based on a multi-threaded implementation. Our new approach takes full advantage of the state-of-the-art fast and optimized YAP Prolog engine and shares the underlying execution environment, scheduler and most of the data structures used to support YapOr's model. Initial experiments with our new approach consistently achieve almost linear speedups for most of the applications, proving itself as a good alternative for exploiting implicit parallelism in the currently available low cost multi-core architectures.

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“…2. Because workers see a contiguous stack, copying imposes less overheads on the engine and has high performance compared to the other approaches (Santos Costa et al 2000). 3.…”

Section: Memory Modelmentioning

confidence: 99%

Threads and or-parallelism unified

Costa¹,

Dutra²,

Rocha³

2010

Theory and Practice of Logic Programming

Self Cite

View full text Add to dashboard Cite

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On applying or-parallelism and tabling to logic programs

Rocha¹,

Silva²,

Costa³

2005

Theory and Practice of Logic Programming

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Logic Programming languages, such as Prolog, provide a high-level, declarative approach to programming. Logic Programming offers great potential for implicit parallelism, thus allowing parallel systems to often reduce a program's execution time without programmer intervention. We believe that for complex applications that take several hours, if not days, to return an answer, even limited speedups from parallel execution can directly translate to very significant productivity gains.It has been argued that Prolog's evaluation strategy -SLD resolution -often limits the potential of the logic programming paradigm. The past years have therefore seen widening efforts at increasing Prolog's declarativeness and expressiveness. Tabling has proved to be a viable technique to efficiently overcome SLD's susceptibility to infinite loops and redundant subcomputations.Our research demonstrates that implicit or-parallelism is a natural fit for logic programs with tabling. To substantiate this belief, we have designed and implemented an or-parallel tabling engine -OPTYap -and we used a shared-memory parallel machine to evaluate its performance. To the best of our knowledge, OPTYap is the first implementation of a parallel tabling engine for logic programming systems. OPTYap builds on Yap's efficient sequential Prolog engine. Its execution model is based on the SLG-WAM for tabling, and on the environment copying for or-parallelism.Preliminary results indicate that the mechanisms proposed to parallelize search in the context of SLD resolution can indeed be effectively and naturally generalized to parallelize tabled computations, and that the resulting systems can achieve good performance on shared-memory parallel machines. More importantly, it emphasizes our belief that through applying or-parallelism and tabling to logic programs the range of applications for Logic Programming can be increased.

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