Lambda Calculus in Core Aldwych

Core Aldwych is a simple model for concurrent computation, involving the concept of agents which communicate through shared variables. Each variable will have exactly one agent that can write to it, and its value can never be changed once written, but a value can contain further variables which are written to later. A key aspect is that the reader of a value may become the writer of variables in it. In this paper we show how this model can be used to encode lambda calculus. Individual function applications can be explicitly encoded as lazy or not, as required. We then show how this encoding can be extended to cover functions which manipulate mutable variables, but with the underlying Core Aldwych implementation still using only immutable variables. The ordering of function applications then becomes an issue, with Core Aldwych able to model either the enforcement of an ordering or the retention of indeterminate ordering, which allows parallel execution

Recursive computation of the invariant measure of a stochastic differential equation driven by a L\'evy process

We investigate some recursive procedures based on an exact or ``approximate'' Euler scheme with decreasing step in vue to computation of invariant measures of solutions to S.D.E. driven by a L\'evy process. Our results are valid for a large class of S.D.E. that can be governed by L\'evy processes with few moments or can have a weakly mean-reverting drift, and permit to find again the a.s. C.L.T for stable processes

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Published in Switzerland by the Small Arms Survey

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Communicating generators in Javascript

This paper outlines the design, performance, and use of an application programming interface and library for concurrent programming with CSP in JavaScript. The implementation harnesses ECMAScript 6 Generators to provide cooperative scheduling and channel communication within a single JavaScript engine. External channels lie atop WebSockets, amongst other web technologies, to enable multicore and distributed execution across standard web browsers and Node.js servers. Low-level benchmarks indicate that scheduling and messaging performance is within expectations for this dynamic and diverse execution environment. Sample code snippets highlight the applicability of CSP to contemporary web development in hiding the location of computation and state through the channel abstraction. The ”callback hell” scenario common to many JavaScript applications is alleviated by using channels instead of callbacks, and the possibility of performing parallel and scientific computing is explored with promising results. Finally, the limitations of the present design are discussed, and possible enhancements such as the dynamic migration of state and code are considered.peer-reviewe

Program and Budget Review Process: Development of the New Procedure

Summary of discussions of the TAC Working Group on the Budget Process at ISNAR Headquarters in January 1986. The purpose of the discussions was to develop a list of essential candidate activities of CGIAR centers, and a set of evaluation and selection criteria with which to rate center activities. These criteria would be used in a proposed new program and budget review process. These discussions were followed by meetings between the TAC working group and a working group of Center Directors at which TAC's evaluation and selection criteria and list of activities were discussed. Annexes include a list of candidate activities, first draft of a systemwide glossary of activities, and two lists of tentative indicators and criteria by the two working groups. Agenda document, TAC 39th Meeting, March 1986

Cache-affinity scheduling for fine grain multithreading

Cache utilisation is often very poor in multithreaded applications, due to the loss of data access locality incurred by frequent context switching. This problem is compounded on shared memory multiprocessors when dynamic load balancing is introduced and thread migration disrupts cache content. In this paper, we present a technique, which we refer to as ‘batching’, for reducing the negative impact of fine grain multithreading on cache performance. Prototype schedulers running on uniprocessors and shared memory multiprocessors are described, and finally experimental results which illustrate the improvements observed after applying our techniques are presented.peer-reviewe