Browsing by Author "West, Darrin"

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    Communicating Sequential Prolog
    (1988-01-01) Li, Xining; Unger, Brian W; Cleary, John; Lomow, Greg; West, Darrin
    Communicating Sequential Prolog (CSP') is a single-solution distributed logic programming language for discrete event simulation. Its primary goal is to speed up the execution of logic programs through the use of parallelism, while as far as possible preserving the semantics of standard Prolog. A CSP' program consists of a set of parallel processes, synchronized by simulation time and by message passing. The underlying interprocess communication mechanism is Time Warp. The pertinent features of parallel logic programming and Time Warp are described. The syntax of CSP' is introduced and the semantics of new predicates and their control structures are discussed. Examples are given to show the expressive power and simplicity of CSP'.
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    Opimising the time wrap using the semantics of abstract data types
    (1986-10-01) West, Darrin; Lomow, Greg; Unger, Brian W
    The Time Warp mechanism for synchronising the execution of simulation components offers significant potential for achieving concurrency within distributed simulations. This mechanism takes advantage of the independence of most events in a simulation, enforcing only a partial ordering of events which allows many events to occur in an arbitrary order. There are many situations, however, where the partial order imposed by Time Warp is too restrictive, i.e., events are unnecessarily forced to occur in a specific order. This paper presents several example situations where Time Warp semantics can be relaxed, describes an approach based on abstract data types that can substantially improve performance, and outlines an implementation of this approach.
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    Optimising time warp: lazy rollback and lazy reevaluation
    (1988) West, Darrin; Unger, Brian W.