A method of describing pictures is introduced. The equations, which describe the appearance of a picture, also form a purely functional program which can be used to compute the set of lines necessary to plot the pictu...
The purpose of this paper is to introduce a notation for expressing the requirements of time-critical systems and a calculus for reasoning about them. The Actions, Events and States of a system are represented by sets...
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We define non-interference in the algebra of CSP;that definition leads to simple proof rules for non-interference concerning, amongst other things, composition of systems exhibiting non-interference. We work through a...
We are aiming at a classification of semantical models for Communicating Processes that will enable us to recommend certain models which are just detailed enough for particular applications. But before such an aim can...
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Timed CSP is a well-known process algebra, built as an extension to Hoare's original CSP, designed to handle concurrency combined with timing considerations. It achieves this over a continuous time domain (the non...
Timed CSP is a well-known process algebra, built as an extension to Hoare's original CSP, designed to handle concurrency combined with timing considerations. It achieves this over a continuous time domain (the non-negative real numbers), which has the drawback of precluding standard model-checking approaches, as the state-space of any process is naturally a priori (uncountably) infinite. This paper shows how to circumvent this problem by translating and reinterpreting timed CSP processes within a new model of standard CSP. In this discrete model, which draws on previous work by A.W. Roscoe (1997) and A. Mukkaram (1993), timing of events is provided by the consistent and regular communication of a special tock event, analogous to the 'tick' of a clock. The various parallel components of a process are therefore required to synchronise on tock, ensuring a uniform rate of passage of time. General results yielding tight bounds on the loss of information inherent to the translation are given.
Binomial filters are simple and efficient structures based on the binomial coefficients for implementing Gaussian filtering. They do not require multipliers and can therefore be implemented efficiently in programmable...
Binomial filters are simple and efficient structures based on the binomial coefficients for implementing Gaussian filtering. They do not require multipliers and can therefore be implemented efficiently in programmable hardware. There are many possible variations of the basic binomial filter structure, and they provide a wide range of space-time trade-offs; a number of these designs have been captured in a parametrised form and their features are compared. This technique can be used for multi-dimensional filtering, provided that the filter is separable. The numerical performance of binomial filters, and their implementation using field-programmable devices for an image processing application, are also discussed.
Some general conditions under which the specification of a concurrent system can be expressed as the conjunction of specifications for its component processes are explored. A lattice-theoretic fixed-point theorem abou...
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Some general conditions under which the specification of a concurrent system can be expressed as the conjunction of specifications for its component processes are explored. A lattice-theoretic fixed-point theorem about increasing functions is proved, and examples of its application in several areas of computing science are given. Some consequences are drawn for the design of concurrent algorithms, high-level programming languages, and fine-grained concurrent computer architectures.< >
The author defines non-interference in the algebra of CSP; that definition leads to simple proof rules for non-interference concerning, amongst other things, composition of systems exhibiting non-interference. The aut...
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The author defines non-interference in the algebra of CSP; that definition leads to simple proof rules for non-interference concerning, amongst other things, composition of systems exhibiting non-interference. The author works through a case study of a multi-level secure system to illustrate those laws.< >
Field programmable gate arrays containing more than one size of lookup-table occupy a large and growing portion of the market, but technology mapping for these architectures has hardly been considered. New algorithms ...
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Field programmable gate arrays containing more than one size of lookup-table occupy a large and growing portion of the market, but technology mapping for these architectures has hardly been considered. New algorithms have been developed for decomposition, covering and restructuring targeted at these architectures. Benchmark results show that the new method produces circuits which are on average 15% smaller than the best previous approach we know of.
We investigate the practical viability of PRAM programming within the BSP framework. We argue that there is a necessity for PRAM computations in situations where the problem exhibits poor data locality. We introduce a...
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We investigate the practical viability of PRAM programming within the BSP framework. We argue that there is a necessity for PRAM computations in situations where the problem exhibits poor data locality. We introduce a C++ PRAM simulator that is built on top of the Oxford BSP Toolset, BSPlib, and provide a succinct PRAM language. Our approach achieves simplicity of programming over direct-mode BSP programming for reasonable overhead cost. We objectively compare optimized BSP algorithms with PRAM algorithms implemented with our library and provide encouraging experimental results for the latter style of programming.
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