Stephen A. Ward

Distributed broadcast channel access

Abstract This paper presents a general approach to sharing a broadcast channel among multiple processors. There are two components to the problem of sharing a single resource: (1) How to specify the usage pattern of the resource; and (2) How to restrict access to the resource so that the specified usage pattern can be realized. One way to solve both of these problems is solved by embodying the desired usage pattern in priority update algorithms which assign unique priorities to all the users. The secobd problem then becomes that of determining the competing user who has the highest priority when the resource is free. Solutions are proposed which promise the combined advantages of ethernet (short message delay) and ringnet (high throughput).

Towards Bayanihan: building an extensible framework for volunteer computing using Java

Project Bayanihan seeks to develop the idea of volunteer computing, which allows people to very easily pool together their computers′ processing power and co-operate in solving parallel problems. While the idea of volunteer computing offers many exciting new prospects in global supercomputing and collaboration, its realization involves many challenging research issues that need to be addressed. In this paper, we present a flexible object-oriented framework using Java and HORB that allows programmers to experiment with different approaches to these issues by simply extending and interconnecting basic library components. We also present results from a distributed web-crawling application written using the framework.

The MuNet: A scalable decentralized architecture for parallel computation

The MuNet is a multiprocessor architecture which can be program-transparently scaled over a very wide cost-performance spectrum. Each processor in a MuNet communicates directly only with a limited number ofneighbors..There is no shared memory, central broadcast medium, or other hardware resource shared equally by all processors In the system. This strictly local communication and interconnection strategy means that only a constant amount of additional hardware need be added for each new processor incorporated into the system. MuNet architectures are significant because of their potential for scalability and large capacity, their way of forging a collection of processors into a coherent programming system, and their ability to support a wide range of object management functions on a distributed system without recourse to any central controlling mechanism. The paper gives an overview of the main structural features of the MuNet, along with a status report on the MuNet project.

Rational clocking [digital systems design]

Communication between independently-clocked digital subsystems typically involves a finite probability of synchronization failure whose minimization introduces delays and consequent performance costs. This paper explores a technique that eliminates both the inherent unreliability of such communication and the performance overhead it implies. Our approach maintains a known phase relationship, between clocks whose frequencies are related by a rational factor, and exploits the predictability of their relative phases to algorithmically time communications without run-time arbitration contests.

A solution to a special case of the synchronization problem

A synchronizer that exhibits an arbitrarily low failure rate and a short propagation delay for the special case of synchronizing a signal that is synchronous with some periodic signal is described. >

A Syntactic Theory of Message Passing

Recent developments by Hewitt and others have stimulated interest in message-passing constructs as an alternative to the more conventional applicative semantics on which most current languages are based. The present work illuminates the distinction between applicative and message-passing semantics by means of the <italic>μ</italic>-calculus, a syntactic model of message-passing systems similar in mechanism to the λ-calculus. Algorithms for the translation of expressions from the λ- to the <italic>μ</italic>-calculus are presented, and differences between the two approaches are discussed. Message-passing semantics seem particularly applicable to the study of multiprocessing. The <italic>μ</italic>-calculus, through the mechanism of <italic>conduits,</italic> provides a simple model for a limited but interesting class of parallel computations. Multiprocessing capabilities of the <italic>μ</italic>-calculus are illustrated, and multiple-processor implementations are discussed briefly.

Set-associative dynamic random access memory

Static-column dynamic RAMs (random-access memories) offer fast access to successive locations within a single row, a fact which has been used in their implementation in fast cacheless memory systems. Such caches are necessarily nonassociative (direct-mapped), limiting their performance relative to set-associative caches of similar total capacity. The authors describe an architecture for dynamic RAM chips which circumvents this limitation by providing several alternative static row buffers on each chip. Cacheless memory systems utilizing these devices are able to achieve the performance characteristics of relatively expensive set-associative cached memories using only economical high-density RAM parts. Simulation results on set-associate dynamic RAMs (SADRAMs) are presented and some plausible roles for SADRAMs in various architectural contexts are noted.<<ETX>>

Real time plotting of approximate contour maps

Scientific Applications Real Time Plotting of Approximate Contour Maps well as the plot resolution at ead~ character position. In general, the approach described requires 6n 2 special characters (plus overstriking) for an order n contour map. Thus order one contour maps may be output via a terminal or other device augmented by six additional characters; a 96-character programmable-font device may be used to produce order four countours.

Clui: a platform for handles to rich objects

On the desktop, users are accustomed to having visible handles to objects that they want to organize, share, or manipulate. Web applications today feature many classes of such objects, like flight itineraries, products for sale, people, recipes, and businesses, but there are no interoperable handles for high-level semantic objects that users can grab. This paper proposes Clui, a platform for exploring a new data type, called a Webit, that provides uniform handles to rich objects. Clui uses plugins to 1) create Webits on existing pages by extracting semantic data from those pages, and 2) augmenting existing sites with drag and drop targets that accept and interpret Webits. Users drag and drop Webits between sites to transfer data, auto-fill search forms, map associated locations, or share Webits with others. Clui enables experimentation with handles to semantic objects and the standards that underlie them.

Vision: a lightweight computing model for fine-grained cloud computing

Cloud systems differ fundamentally in how they offer and charge for resources. While some systems provide a generic programming abstraction at coarse granularity, e.g., a virtual machine rented by the hour, others offer specialized abstractions with fine-grained accounting on a per-request basis. In this paper, we explore Tasklets, an abstraction for instances of short-duration, generic computations that migrate from a host requiring computation to hosts that are willing to provide computation. Tasklets enable fine-grained accounting of resource usage, enabling us to build infrastructure that supports trading computing resources according to various economic models. This computation model is especially attractive in settings where mobile devices can utilize resources in the cloud to mitigate local resource constraints.