Abstract
Most models that have been proposed, or implemented, so far for exploiting both or-parallelism and independent and-parallelism have only considered pure logic programs (pure Prolog). We present an abstract model, called the Composition-Tree, for representing and-or parallelism in full Prolog. The Composition-Tree recomputes independent goals to ensure that Prolog semantics is preserved. We combine the idea of Composition-Tree with ideas developed earlier, to develop an abstract execution model that supports full Prolog semantics while at the same time avoiding redundant inferences when computing solutions to (purely) independent and-parallel goals. This is accomplished by sharing solutions of independent goals when they are pure (i.e. have no side-effects or cuts in them). The Binding Array scheme is extended for and-or parallel execution based on this abstract execution model. This extension enables the Binding Array scheme to support or-parallelism in the presence of independent and-parallelism, both when solutions to independent goals are recomputed as well as when they are shared. We show how extra-logical predicates, such as cuts and side-effects, are supported in this model. © 1994.

Abstract

Abstract

Abstract
Recently, new parallel architectures, namely distributed shared memory architectures, have been proposed and built. These combine the ease-of-use of shared memory architectures with the scalability of the message-passing architectures. These architectures provide software and hardware support for shared virtual address space on physically distributed memory. This paper describes Dorpp, an execution model that supports or-parallelism for these machine architectures, namely for the EDS parallel machine. Dorpp uses a shared memory model for or-parallelism. It attempts, however, at exploiting locality and at reducing communication overheads through scheduling and by caching accesses to remote shared data. The problem of memory coherency of cached data is discussed and solutions are proposed. Preliminary evaluation results of the execution model through simulation are presented. © Springer-Verlag Berlin Heidelberg 1993.

Abstract

Abstract