Parallel Bounded Quantiication|preliminary Results

We have extended D. H. D. Warren's abstract machine for sequential Prolog with parallel instructions that implement bounded quantiica-tions, an extension to Prolog proposed by Barklund and Bevemyr. These instructions are intended for parallel computers supporting the data parallel programming model. Luther, an emulator for the sequential abstract machine implemented in the C programming language, has been extended with these instructions, implemented in the data parallel C* programming language. We have coded three example programs that use bounded quan-tiications, and run them in the emulator on a Connection Machine model 200, a SIMD parallel computer. We compare the run times on this parallel computer with the run times obtained with a sequential implementation of bounded quantiications on a SUN-4M sequential computer. The best result is that one parallel bounded quantiication program runs 30 times faster on the Connection Machine than an ordinary recursive program implementing the same algorithm running on the sequential computer. It is conceivable that one can obtain far higher speed-ups when running on larger data parallel computers using bounded quantiications. 1 INTRODUCTION Recently, Barklund & Millroth (1992) have proposed bounded quantiica-tions as an extension to sequential and parallel logic programming languages. Barklund & Bevemyr (1992) have deened a particular extension of Prolog with bounded quantiications and also deened extensions to D. H. D. Warren's sequential abstract Prolog machine (1983), a.k.a. WAM, that implement this extension. The resulting language is a strict superset of Pro-log where some computations which otherwise would be written as recursive programs can instead be written as bounded quantiications. The program