Abstract State Machines 1988-1998: Commented ASM Bibliography

An annotated bibliography of papers which deal with or use Abstract State Machines (ASMs), as of January 1998.Comment: Also maintained as a BibTeX file at http://www.eecs.umich.edu/gasm

Distributed Logic Objects: A Fragment of Rewriting Logic and its Implementation

Abstract This paper presents a logic language (called Distributed Logic Objects, DLO for short) that supports objects, messages and inheritance. The operational semantics of the language is given in terms of rewriting rules acting upon the (possibly distributed) state of the system. In this sense, the logic underlying the language is Rewriting Logic. In the paper we discuss the implementation of this language on distributed memory MIMD architectures, and we describe the advantages achieved in terms of flexibility, scalability and load balancing. In more detail, the implementation is obtained by translating logic objects into a concurrent logic language based on multi-head clauses, taking advantage from its distributed implementation on a massively parallel architecture. In the underlying implementation, objects are clusters of processes, objects' state is represented by logical variables, message-passing communication between objects is performed via multi-head clauses, and inheritance is mapped into clause union. Some interesting features such as transparent object migration and intensional messages are easily achieved thanks to the underlying support. In the paper, we also sketch a (direct) distributed implementation supporting the indexing of clauses for single-named methods

Automatic goal distribution strategies for the execution of committed choice logic languages on distributed memory parallel computers

There has been much research interest in efficient implementations of the Committed Choice Non-Deterministic (CCND) logic languages on parallel computers. To take full advantage of the speed gains of parallel computers, methods need to be found to automatically distribute goals over the machine processors, ideally with as little involvement from the user as possible.In this thesis we explore some automatic goal distribution strategies for the execu¬ tion of the CCND languages on commercially available distributed memory parallel computers.There are two facets to the goal distribution strategies we have chosen to explore:DEMAND DRIVEN: An idle processor requests work from other processors. We describe two strategies in this class: one in which an idle processor asks only neighbouring processors for spare work, the nearest-neighbour strategy; and one where an idle processor may ask any other processor in the machine for spare work, the allprocessors strategy.WEIGHTS: Using a program analysis technique devised by Tick, weights are attached to goals; the weights can be used to order the goals so that they can be executed and distributed out in weighted order, possibly increasing performance.We describe a framework in which to implement and analyse goal distribution strategies, and then go on to describe experiments with demand driven strategies, both with and without weights. The experiments were made using two of our own implementations of Flat Guarded Horn Clauses — an interpreter and a WAM-like system — executing on a MEIKO T800 Transputer Array configured in a 2-D mesh topology.Analysis of the results show that the all-processors strategies are promising (AP-NW), adding weights had little positive effect on performance, and that nearest-neighbours strategies can reduce performance due to bad load balancing.We also describe some preliminary experiments for a variant of the AP-NW strategy: goals which suspend on one variable are sent to the processor that controls that variable, the processes-to-data strategy. And we briefly look at some preliminary results of executing programs on large numbers of processors (> 30)

A distributed Linda server on a network of heterogeneous processors

Linda is an approach to parallelism which relies on a virtual associative shared memory called tuple space. Tuple space is accessed through a small set of primitive operations and is conceptually easy to understand and manipulate. The physical implementation of a Linda tuple space may of course be completely different from the conceptual model. Rhodes has implemented versions of Linda on a ring of RS-232 joined PC's and on a cluster of T800 transputers with a single copy of tuple space on one transputer. Current research targets the implementation of a distributed Linda server on a network of heterogeneous processors. This work describes the design and implementation of a distributed Linda server. Emphasis is placed on aspects of the design which enhance portability and efficiency

Literature Review For Networking And Communication Technology

Report documents the results of a literature search performed in the area of networking and communication technology