A Simple and Efficient Implementation of Concurrent Local Tabling

Marques, Rui; Swift, Terrance; Cunha, José C.

doi:10.1007/978-3-642-11503-5_22

Cited by 7 publications

(8 citation statements)

References 12 publications

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“…Note that our goal with these experiments is not to prove that we can speedup the execution of tabled programs, despite this is an obvious goal of having a concurrent implementation. Other works have already showed the parallel capabilities of the use of multithreaded tabling [8,9]. Since parallelism is highly dependent on the available concurrency that programs have and on the way synchronization is done, we can easily select/construct programs where linear speedups can be achieved or, on the other hand, where no speedups exist.…”

Section: Resultsmentioning

confidence: 99%

On the Correctness and Efficiency of Lock-Free Expandable Tries for Tabled Logic Programs

Areias

Rocha

2014

Practical Aspects of Declarative Languages

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Tabling is an implementation technique that improves the declarativeness and expressiveness of Prolog in dealing with recursion and redundant sub-computations. A critical component in the implementation of an efficient tabling framework is the design of the data structures and algorithms to access and manipulate tabled data. One of the most successful data structures for tabling is tries. In previous work, our initial approach to deal with concurrent table accesses, implemented on top of the Yap Prolog system, was to use lock-based trie data structures. In this work, we propose a new design based on lock-free data structures and, in particular, we focus our discussion on the correctness and efficiency of extending Yap's tabling framework to support lock-free expandable tries. Experimental results show that our new lock-free design can effectively reduce the execution time and scale better, when increasing the number of threads, than the original lock-based design.

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Section: Resultsmentioning

confidence: 99%

On the Correctness and Efficiency of Lock-Free Expandable Tries for Tabled Logic Programs

Areias

Rocha

2014

Practical Aspects of Declarative Languages

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“…Variant sub-computations by other threads are resolved by consuming the answers stored by the generator thread. When a set of sub-computations being computed by different threads is mutually dependent, then a usurpation operation [12] synchronizes threads and a single thread assumes the computation of all sub-computations, turning the remaining threads into consumer threads. This maintains the correctness of the table space but has a major disadvantage: it restricts the potential of concurrency to non-mutually dependent sub-computations.…”

Section: Xsb's Approach To Multithreaded Tablingmentioning

confidence: 99%

On scaling dynamic programming problems with a multithreaded tabling Prolog system

Areias

Rocha

2017

Journal of Systems and Software

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Tabling is a powerful implementation technique that improves the declarativeness and expressiveness of traditional Prolog systems in dealing with recursion and redundant computations. It can be viewed as a natural tool to implement dynamic programming problems, where a general recursive strategy divides a problem in simple sub-problems that are often the same. When tabling is combined with multithreading, we have the best of both worlds, since we can exploit the combination of higher declarative semantics with higher procedural control. However, at the engine level, such combination for dynamic programming problems is very difficult to exploit in order to achieve execution scalability as we increase the number of running threads. In this work, we focus on two well-known dynamic programming problems, the Knapsack and the Longest Common Subsequence problems, and we discuss how we were able to scale their execution by using the multithreaded tabling engine of the Yap Prolog system. To the best of our knowledge, this is the first work showing a Prolog system to be able to scale the execution of multithreaded dynamic programming problems. Our experiments also show that our system can achieve comparable or even better speedup results than other parallel implementations of the same problems.

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“…The idea behind the Concurrent Local evaluation is that when a thread T encounters a (shared) tabled subgoal S that has not been encountered by any thread, T evaluates S. Other threads are allowed to use the table for S only after T has completed S. Concurrency control for tables mainly arises when more than one thread evaluates different tabled subgoals in the same SCC simultaneously. In this case a deadlock would occur, which the engine detects and resolves so that a single thread assumes computation of all tabled subgoals in the SCC (Marques and Swift 2008;Marques et al 2010). For example, in Figure 2 such a situation would occur if a thread T 1 called reach(1,Y) and another called reach(3,Y) before it was called by T 1 .…”

Section: Multi-threadingmentioning

confidence: 99%

XSB: Extending Prolog with Tabled Logic Programming

Swift¹,

Warren²

2011

Theory and Practice of Logic Programming

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146

128

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The paradigm of Tabled Logic Programming (TLP) is now supported by a number of Prolog systems, including XSB, YAP Prolog, B-Prolog, Mercury, ALS, and Ciao. The reasons for this are partly theoretical: tabling ensures termination and optimal known complexity for queries to a large class of programs. However, the overriding reasons are practical. TLP allows sophisticated programs to be written concisely and efficiently, especially when mechanisms such as tabled negation and call and answer subsumption are supported. As a result, TLP has now been used in a variety of applications from program analysis to querying over the semantic web. This paper provides a survey of TLP and its applications as implemented in the XSB Prolog, along with discussion of how XSB supports tabling with dynamically changing code, and in a multi-threaded environment.

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A Simple and Efficient Implementation of Concurrent Local Tabling

Cited by 7 publications

References 12 publications

On the Correctness and Efficiency of Lock-Free Expandable Tries for Tabled Logic Programs

On the Correctness and Efficiency of Lock-Free Expandable Tries for Tabled Logic Programs

On scaling dynamic programming problems with a multithreaded tabling Prolog system

XSB: Extending Prolog with Tabled Logic Programming

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