Abstract

Abstract

Abstract
We present the architecture of a parallel programming system, the di_pSystem. Our target machine consists of clusters of multiprocessors interconnected with very fast networks. The system aims to provide a programming style close to the shared memory programming model. This is achieved by a software layer between the programmer and the operating system that supports the communication between individual computational agents and that dynamically balances the work-load in the system. This layer effectively hides much of the complexity of programming distributed architectures from the programmer while being competitive in performance. The low-level communication in the di_pSystem is implemented using MPI as a backbone. Initial results indicate that the system is close in performance to MPI, a fact that we attribute to its ability to dynamically balance the work-load in the computations. © Springer-Verlag Berlin Heidelberg 1999.

Abstract
YapOr is an or-parallel system that extends the Yap Prolog system to exploit implicit or-parallelism in Prolog programs. It is based on the environment copying model, as first implemented in Muse. The development of YapOr required solutions for some important issues, such as designing the data structures to support parallel processing, implementing incremental copying technique, developing a memory organization able to answer with efficiency to parallel processing and to incremental copying in particular, implementing the scheduler strategies, designing an interface between the scheduler and the engine, implementing the sharing work process, and implementing support to the cut builtin. An initial evaluation of YapOr performance showed that it achieves very good performance on a large set of benchmark programs. Indeed, YapOr compares favorably with a mature parallel Prolog system such as Muse, both in terms of base speed and in terms of speedups. © Springer-Verlag Berlin Heidelberg 1999.

Abstract
Despite extensive theoretical work on process-calculi, virtual machine specifications and implementations of actual computational models are still scarce. This paper presents a virtual machine for a strongly typed, polymorphic, concurrent, object-oriented programming language based on the TyCO process calculus. The system runs byte-code files, assembled from an intermediate assembly language representation, which is in turn generated by a compiler. Code optimizations are provided by the compiler coupled with a type-inference system. The design and implementation of the virtual machine focuses on performance, compactness, and architecture independence with a view to mobile computing. The assembly code emphasizes readability and efficient byte code generation. The byte code has a simple layout and is a compromise between size and performance. We present some performance results and compare them to other languages such as Pict, Oz, and JoCaml.

Abstract
One important advantage of logic programming is that it allows the implicit exploitation of parallelism. Towards this goal, we suggest that or-parallelism can be efficiently exploited in tabling systems and propose two alternative approaches, Or-Parallelism within Tabling (OPT) and Tabling within Or-Parallelism (TOP). We concentrate on the fundamental concepts of an environment copying based model to implement the OPT approach and introduce the data structures and algorithms necessary to extend the YapOr Or-Parallel system, in order to obtain a parallel tabling system.