Abstract
Andorra-I is an experimental parallel Prolog system that transparently exploits both dependent and-parallelism and or-parallelism. It constitutes the first implementation of the Basic Andorra model, a parallel execution model for logic programs in which determinate goals are executed before other goals. This model, besides combining two of the most important forms of implicit parallelism in logic programs, also provides a form of implicit coroutining. This means that Andorra-I not only supports standard Prolog but also provides the capabilities of flat committed-choice languages. In this paper, we discuss the main issues involved in the implementation of the Andorra-I engine, covering both the sequential version which runs on uniprocessors and the parallel version which runs on shared-memory multiprocessors such as Sequent Symmetry. We then present performance data for our implementation. This data shows that Andorra-I, an interpreter, has a single-processor performance similar to the comparable sequential system, C-Prolog, while on multiple processors Andorra-I is able to obtain good speedups from both and-parallelism and or-parallelism. In suitable cases, the speedup obtained from exploiting both forms of parallelism combined is better than that obtainable from exploiting either kind alone.

Abstract

Abstract

Abstract

Abstract
This work describes a disk-resident database for Prolog which uses mechanisms similar to the ones used by the clausal database for recording and retrieving terms. It is intended to be used by applications requiring a flexibility greater than that provided by an interface to traditional database system. There is almost no restriction on the terms stored in the database and the retrieval mechanisms produces terms in the order they were recorded. To enhance the performance of the system, the database organization provides an access mechanism using hash-codes on ”key” arguments of the recorded term. The database also provides basic support for multi-user access. © Springer-Verlag Berlin Heidelberg 1989.