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.

Abstract

Abstract

Abstract
Andorra-I is an experimental parallel Prolog system which transparently exploits both dependent and-parallelism and or-parallelism. One of the main components of Andorra-I is its preprocessor. In order to obtain efficient execution of programs in Andorra-I, the preprocessor includes a compiler for Andorra-I. The compiler includes a determinacy analyser and a clause compiler, and generates code for a specialised abstract machine. In this paper we discuss the main issues in the Andorra-I compiler, presenting its abstract instruction set and describing the algorithms used in its implementation.

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
Parallel logic programming (PLP) systems have obtained good performance on traditional bus-based shared-memory architectures. However, the scalable multiprocessors being developed today pose new challenges. Our experience with a sophisticated PLP system, Andorra-I, demonstrates that indeed performance suffers greatly on modern architectures. In order to improve performance, we perform a detailed analysis of the cache behaviour of all Andorra-I data structures via execution-driven simulation of a DASH-like multiprocessor. Based on this analysis we optimise the Andorra-I code using 5 different techniques. Our results show that the techniques provide significant performance improvements, leading to the conclusion that PLP systems can and should perform well on modern scalable multiprocessors.