Parlog86 and the dining logicians

Abstract

A classic problem in concurrent programming is that of the "dining philosophers" which challenges the power of any aspiring concurrent program language. Recently, a growing number of logic programming languages have been refined to handle concurrent programming, one in particular is Parlog86.With the increased sophistication demanded from software, in particular system cum environment software, it is increasingly complex and all too often bug-ridden. In theory, many approaches have been proposed for debugging and increasing confidence in the correctness of a program, some dealing with programming methodology and others with algebraic proof that a program does what the specification intends of it. In practice, for large programs, the most widely used methods are comprehensive test data and tracing of the computation. The art of bug detection with profilers, mutations, bounty hunters, and black teams has become a jargon generator in its own right. Increasingly, software developers begin with a specification of the functionality required by the software. Automatic verified code generation from a specification appears to be an emerging trend with sales of programmer workbenches gaining ground. An attractive alternative is a runnable specification combined with automatic, logically sound transformation from working specifications to efficient programs. There is a body of opinion (e.g., [9] and [20]), holding the belief that logic programs provide such runnable specifications.Insight into the relationship between specifications and programs can be drawn from some definitions proposed by Hoare [16] in relation to the concurrent programming language CSP. "A specification is a predicate describing all observations of a complex system." The predicate could be generalized into a set of logical formulas or sentences, but Hoare goes on to effectively include this possibility: "Specifications of complex sysFurlhfjr information conceriiing publications relating lo Parlog and details of the softwaro available can be obtained by writing lo .

Linda in context

“…In the next section, we discuss parallel logic programming. We focus here on the programming examples presented in a recent article on Parlog [30], contrasting them with Linda's solutions to the same problems. In the last section we discuss pure functional programming, again comparing a Linda and a purely functional solutilm to the same problem, and discussing the implications of the comparison.…”

“…The Japanese Institute for New Generation Computer Technology (ICOT) continues work on their Parallel Inference Machine, which is intended for concurrent logic programming. A recent Communications of the ACM article discussed the new concurrent logic language Parlog [30], and collected papers on one of the first of these languages, Concurrent Prolog, have just been published (complete in 1,178 pages) by MIT Press [31]. Several years ago we published a brief discussion contrasting Concurrent Prolog with Linda [17], but new developments make a comparison between Linda and some of the Parlog solutions recently featured in Communications seem desirable.…”

Logic, Algebra, and Computation

“…A weaker language may need extra-lingual facilities to compensate for its lack of expressiveness. It is an extension of an earlier chart by Ringwood [148]. Notable efforts which and extended by Saraswat [158].…”

“…The PARLOG language [21), described in Section 18, preceded GHC, but went through several evolutions that made it closer to GHC [24,66,148). In the earlier definition [21), referred to as PARLOG83 by [148], the output mechanism was assignment, rather than unification.…”

Parallel branch-and-bound search in Parlog

“…In our examples we shall use the flat Parlog-86 of Ref. 4 with syntax derived from the commercial version of this language, Strand, except that ~ is used in the place to :-to distinguish Parlog from Prolog programs. This gives us: This is essentially a hand-compilation of the OR-parallelism of Program I using the principle of converting OR-parallelism into AND-parallelism outlined in Ref.…”