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.

Abstract
This paper presents DAOS, a model for exploitation of Andand Or-parallelism in logic programs. DAOS assumes a physically distributed memory environment and a logically shared address space. Exploiting both major forms of implicit parallelism should serve a broadest range of applications. Besides, a model that uses a distributed memory environment provides scalability and can be implemented over a computer network. However, distributed implementations of logic programs have to deal with communication overhead and inherent complexity of distributed memory managent. DAOS overcomes those problems through the use of a distributed shared memory layer to provide single-writer, multiple-readers sharing for the main execution stacks combined with explicit message passing for work distribution and management.

Abstract

Abstract

Abstract
Byte-code representation has been used to implement several programming languages such as Lisp, ML, Prolog, or Java. In this work, we discuss the impact of several emulator optimisations for the Prolog system YAP YAP obtains performance comparable or exceeding well-known Prolog systems by applying several different styles of optimisations, such as improving the emulation mechanism, exploiting the characteristics of the underlying hardware, and improving the abstract machine itself. We give throughout a detailed performance analysis, demonstrating that low-level optimisations can have a very significant impact on the whole system and across a range of architectures.