Abstract
Practical Prolog programs usually contain extra-logical features like cuts, side-effects, and database manipulating predicates. In order to exploit implicit parallelism from real applications while preserving sequential Prolog semantics, a parallel logic programming system should necessarily support these features. In this paper we show how Prolog's extra-logical features can be supported in an and-or parallel logic programming system. We show that to support extra-logical features an and-or parallel logic programming system should recompute the solutions to independent goals instead of sharing them. We describe an abstraction called the composition tree for representing and-or parallel execution with recomputation. We introduce the notion of ''local-leftmostness'' in the composition tree and use it for deriving complete and efficient methods for supporting extra-logical predicates in and-or parallel logic programming systems based on the composition tree abstraction.

Abstract
We propose dynamic compilation for Prolog, in the style of Just-In-Time compilers. Our approach adapts to the actual characteristics of the target program by (i) compiling only the parts of the program that are executed frequently, and (ii) adapting to actual call patterns. This allows aggressive optimization of the parts of the program that are really executed, and better informed heuristics to drive these optimizations. Our compiler does need to support all features in the language, only what is deemed important to performance. Complex execution patterns, such as the ones caused by error handling, may be left to the interpreter. On the other hand, compilation is now part of the run-time, and thus incurs run-time overheads. We have implemented dynamic compilation for YAP system. Our initial results suggest that dynamic compilation achieves very substantial performance improvements over the original interpreter, and that it can approach and even out-perform state-of-the-art native code systems. We believe that we have shown that dynamic compilation is worthwhile and fits naturally with Prolog execution.

Abstract
A critical issue in the design of logic programming systems is their memory performance, both in terms of total memory usage and locality in memory accesses. BEAM, as most modern Prolog systems, requires both good emulator design and good memory performance for best performance. We report on a detailed study of the memory management techniques used on our sequential implementation of the EAM. We address questions like how effective are the techniques the BEAM uses to recover and reuse memory space, how garbage collection affects performance and how to classify and unify variables in a EAM environment. We also propose a finer variable allocation scheme to reduce memory overheads that is quite effective at reducing memory pressure, with only a small overhead.

Abstract

Abstract

Abstract
In this work we investigate how different machine settings for a hardware Distributed Shared Memory (DSM) architecture affect the performance of parallel logic programming (PLP) systems. We use execution-driven simulation of a DASH-like multiprocessor to study the impact of the cache block size, the cache size, the network bandwidth, the write buffer size, and the coherence protocol on the performance of Andorra-I, a PLP system capable of exploiting implicit parallelism in Prolog programs. Among several other observations, we find that PLP systems favour small cache blocks regardless of the coherence protocol, while they favour large cache sizes only in the case of invalidate-based coherence. We conclude that the cache block size, the cache size, the network bandwidth, and the coherence protocol have a significant impact on the performance, while the size of the write buffer is somewhat irrelevant.