Dependent And-parallelism Research Articles

Overview of DASWAM: Exploitation of dependent and-parallelism

The Dynamic Dependent And-parallel Scheme (DDAS) is a parallel execution scheme for Prolog that is designed to exploit independent and dependent and-parallelism in full Prolog programs. In this paper, an overview of some techniques for implementing DDAS is presented. The main purpose of these techniques is to provide reasonably efficient methods for implementing the idea of the dependent status and the dynamic detection of the leftmost instance of a variable, along with the techniques needed for suspending and waking up of goals. DASWAM, an implementation of DDAS using the techniques presented in this paper, is based on modifying the Warren Abstract Machine (WAM) for parallel execution, and is designed to execute programs efficiently. A prototype DASWAM has been implemented, and results on running significant application programs presented in this paper suggest that it is possible to implement DASWAM efficiently, and that significant parallelism can be extracted.

Andorra-I compilation

Andorra-I is an experimental parallel Prolog system which transparently exploits both dependent and-parallelism and or-parallelism. One of the main components of Andorra-I is its preprocessor. In order to obtain efficient execution of programs in Andorra-I, the preprocessor includes a compiler for Andorra-I. The compiler includes a determinacy analyser and a clause compiler, and generates code for a specialised abstract machine. In this paper we discuss the main issues in the Andorra-I compiler, presenting its abstract instruction set and describing the algorithms used in its implementation.

Parallel inference algorithms for the connection method on systolic arrays

In practice, various techniques are used to speed up the reasoning in logic programming and parallel machines. Three major approaches have generally been adapted to solve this problem. The most common approach involves some methods of the development of AND and OR parallelism, as in Parlog[Clark84], Concurrent-Prolog[Shapiro83] and IDIOM[Gupta&Hermenegildo]. In these schemes, the three main forms of implicit parallelism-Independent AND-Parallelism, Dependent AND-parallelism and OR-parallel-ism are exploited. The second approach is to build parallel architectures to execute different level parallelism inherent in inference, such as DADO[Stolfo84, Miranker90], NON-VON[Hillyer86] and PSM[Gupta87]. The third approach is to develop faster match and search algorithms, as in Rete[Forgy82] and Treat The bottle-neck in inference systems is the match phase. Around 90% of execution time is consumed in this phase[Gupta87]. In this paper, we present algorithms to realize the connection method on systolic arrays. The a...

And/Or parallel execution of logic programs

This paper proposes a new And/Or parallel execution model (FORDAP) for logic programs which can not only exploit full Or- and independent And-parallelism, but also can exploit dependent And-parallelism with a limited increment of runtime cost. A synchronization mechanism is constructed on a shared variable between its producer and its consumers and a consumer with a large granularity is decomposed further to let its subgoals independent to that producer to execute without delay. A granularity computation algorithm is presented for the control of a goal's decomposition.

An abstract prolog machine based on parallel resolution principle

We describe an abstract machine, called SPUM, for the AND parallel execution of Prolog programs. We also present a resolution algorithm for logic programs, on which the SPUM architecture is based. The algorithm, called SPU, is based on parallel resolution principle and allows parallel execution of unificationsof a deterministic path of the proof tree, giving in effect dependent and-parallelism. We also present preliminary results which are indicative of the performance expected from SPUM.

A logic programming language based on the Andorra model

The Andorra model is a parallel execution model of logic programs which exploits the dependent and-parallelism and or-parallelism inherent in logic programming. We present a flat subset of a language based on the Andorra model, henceforth called Andorra Prolog, that is intended to subsume both Prolog and the committed choice languages. Flat Andorra, in addition todon’t know anddon’t care nondeterminism, supports control of or-parallel split, synchronisation on variables, and selection of clauses. We show the operational semantics of the language, and its applicability in the domain of committed choice languages. As an examples of the expressiveness of the language, we describe a method for communication between objects by time-stamped messages, which is suitable for expressing distributed discrete event simulation applications. This method depends critically on the ability to expressdon’t know nondeterminism and thus cannot easily be expressed in a committed choice language.