OCCAM 2: an overview from a software engineering perspective

The programming language OCCAM has been developed for the design and implementation of systems of concurrent processes communicating over channels. It is primarily intended for use as a programming language for the Inmos transputer. This paper has two aims: to review the major features of OCCAM, and to show how the language relates to various stages of the software development process. It also reviews some of the decisions in the design of the language in the light of the criteria outlined in the introductory paper to this series on high-level languages.     

使用“通信顺序进程”机制的神经网络仿真

本文引入了“通信顺序进程”的概念，同时介绍了一种实现环境－ＲＩＳＣ结构的Ｔｒａｎｐｕｔｅｒ处理器及Ｏｃｃａｍ并行化编程语言，并阐述了用“通信顺序进程”机制来仿真人工神经网络的方法。     

An array processing language for transputer networks

Networks of transputers are often used for array processing applications. Programming such systems in OCCAM can be tedious and error-prone. This paper outlines a language designed to facilitate the solution of problems which involve some array processing. The language is called LATIN, and is currently being implemented on a transputer network. An example of its use is given.     

分布式并行处理和多晶片机系统

本文首先描述以CSP 理论为基础的一种经命名通道通信、有层次结构的分布式并行处理模型,然后详细分析、归纳occam 语言和晶片机(transputer)为支持和实现这种并行处理模型所具有的结构特征,并以具体系统为例探讨了以晶片机为结构组件构造的多晶片机系统在系统结构上的一般特性。对于多晶片机系统在九十年代可能的发展变化,也作了简要的分析评估。     

Flat Concurrent Prolog on transputers

Flat Concurrent Prolog (FCP) is a general purpose logic programming language designed for concurrent programming and parallel execution. Staring with a concise introduction of the language and its underlying computational model we describe how to implement a distributed FCP interpreter on a transputer environment using OCCAM. Basic techniques we used for exploiting and controlling parallelism are explained in terms of an abstract architecture. The result of mapping this abstract model on transputers is presented as concrete architecture. Substantial design issues are considered in detail.     

A parallel architecture for distributed adaptive control

This paper describes the development of a flexible control system based on multiple T800 floating point transputers. In Part 1 of this paper, entitled 'The application of transputers to distributed control', an overview has been presented of distributed command and control systems (DCCS) and the suitability of the transputer for implementation within such systems discussed. In Part 2 of the article a transputer-based control module which has been developed at the University of Paisley is described. The module allows a number of different modes of operation in that it can be configured to act as either a fixed controller with the coefficients being down-loaded from a central control station, or as an adaptive controller which can make use of an explicit pole placement or linear quadratic Gaussian (LQG) structure. A supervisor, or coordination level, is incorporated into the adaptive controller to monitor the various parameters produced within the controller and direct the system to maintain a safe operation. This improves the applicability, robustness and integrity of the controller in real-time applications. The ease with which software tasks can be distributed over different transputer architectures allows the same software to be configured to accommodate between one and four transputers within the module. In this way the controller module can utilize a number of different transputer configurations depending on cost/performance trade-offs.The use of the transputer also allows the controller to communicate easily through its serial links with other controllers, hosts and external devices. In this way the module can be used as a universal controller node which can be easily incorporated into a large DCCS. Software has been developed to facilitate the production of this type of integrated environment such that a central network interface can initialize, analyse and supervise a number of the controller modules.     

OCCAM-an overview

The language OCCAM has been developed on the basis of communication and concurrency. OCCAM describes the structure of a system of connected microcomputers. It can also be used to program the individual computers. In addition, OCCAM is a design formalism. Its formal semantics allows a program to be read either as a set of commands or as a predicate in an extension of the predicate calculus. The semantics provides a set of rules for transforming programs.The initial implementation of OCCAM is described. Examples are given of its use in a concurrent system and for program transformation.     

The application of transputers to distributed control

This paper describes the development of a flexible control system based on multiple T800 floating point transputers and is presented in two parts. In part 1 of the paper an overview is presented of distributed command and control systems (DCCS) and the suitability of the transputer for implementation within such systems discussed. It is concluded in this initial investigation that the transputer is ideally suited for use in such systems as it is not only a very powerful processing device but the addition of serial communication links allows individual control modules to easily communicate with other controllers, hosts and external devices. In part 2 of the article, entitled 'A parallel architecture for distributed adaptive control', a transputer-based adaptive control module which has been developed is described. The integration of this flexible controller into a distributed control system is also discussed.     

Interfacing transputer links to external devices

Two approaches to interfacing transputers to external circuitry are considered. The design and construction of both a serial and a parallel interface for transputers is described. These enable transputers to communicate with peripherals via the standard Inmos transputer links. A Motorola MC68701 8-bit microcomputer, serving as a programmable I/O controller, is incorporated into both interfaces. This solution lends a high degree of flexibility into the interface design, and can be used with any transputer board which has spare links available at edge connectors. Finally, two control applications are briefly described which utilize the interfaces.     

A visual tracking system for the measurement of dynamic structural displacements

A transputer-based system has been developed for the measurement of dynamic displacements in real time by visually tracking moving objects from a video Input. Parallel processing techniques have been used to track multiple objects at frame rate, and various predictive tracking algorithms have been assessed and implemented on the transputer network. The system is primarily intended for applications such as the monitoring or testing of large physical structures where actual displacements may not easily be otherwise determined. Results from the monitoring of the behaviour of the Humber Bridge at the centre of its span are presented.     

一组移动代理的行为设计模式

模式是开发应用程序时所用方法和指导原则的总称，它表达了人们的进行软件开发过程中常用的一些设计思想，通过分析移动代理的运行过程，提出了一组行为设计模式，其核心思想就是将系统易变的部分与不变的部分进行分离，将系统不同层次的功能进行分离，具全来说，就是按照从上到下的顺序，将移动代理的行为分成任务流、协作交流和基础功能三层，并针对不同的层提出了相应的设计思想，利用这些模式，人们可以解决移动代理系统设计过程中遇到的许多问题，因此具有很高的实用价值和理论价值。     

The Radon transform on a dynamically switched transputer network

Previously reported work resulted in a transputer tree network using thirty tramputers to perform the Radon transform. The Radon transform was used to enhance linear features in noisy synthetic aperture radar images. The work presented here describes modification of the transputer network by the addition of INMOS B004 link switches, and controlling T222 transputer. The tree configuration is replaced such that link switches now dynamically switch between the image data source transputer (farmer) and the transputers which perform the calculations (workers). It is shown that this arrangement is more cost-effective since the worker transputers are all relieved of their data-routing role. The paper Includes a comparison of the previous tree network with the new switched network, and presents results for both techniques.     

用SQUID架构本地信息代理服务器

仿照电视广播里的插播模式,我们设想了一个活动的代理中心结构作为支持本地信息高效传送的手段,当网页通过与内容服务器协作的动态代理服务器被取回的时候,当地信息将基于需要灵活地被插入到网页中。本文介绍了用Squid—based架构的代理服务器上的信息传送的设计和各种功能,这种方案的操作对于网页客户与内容提供商来说完全透明的,是切实可行的。     

OCCAM solves classical operating system problems

Strictly sequential software is a thing of the past. The development of the OCCAM language, and of the Transputer for implementing it, has made parallel microprocessing a practical alternative to more traditional methods. The fundamentals of OCCAM are outlined. An OCCAM-based approach to solving a multiplexer problem is compared with a PASCAL-based approach. The advantages of replacing PASCAL constructs with OCCAM equivalents (eg semaphores with channels) are emphasized, OCCAM is seen as the herald of truly fifth-generation computers.     

PReSENt: A Collaboration Framework for Resource Sharing in Wireless Mesh Networks

Many protocol particulars developed for the wireless mesh networks, such as multi-path routing, channel assignment, topology control, assume that a network-wide collaboration is available to establish connections to the network outside. However, the collaboration can be easily discouraged in the presence of selfish behaviors, referred to as free-riding. In this paper, we propose a framework, PReSENt, to promote and make more secure the practices of collaboration among nodes by securing a compensation to the collaboration. When the PReSENt is enabled in wireless mesh networks, a node accumulates credits, an amount quantifying its resource provision when it provides its resource for other nodes. The nodes consuming the resource publish rewards, an amount quantifying their resource usage. The credits are used to guarantee the resource sharing for the provider from the customers in the future, whose amount is proportional to its relative contribution to the network-wide collaboration. The rewards are used to validate their corresponding credits in order to prevent false accumulations of the credits in selfish nodes. We formally define the underlying security model of the PReSENt and prove that the PReSENt is secure in the random oracle model. We then implement the PReSENt in J-Sim to illustrate its operational behaviors with respect to correct and secure resource sharing.     

Evaluating computation/communication balance in an object recognition task

I present performance measurements for some compute- and communications-intensive image processing tasks required by an object recognition application. The application was implemented as a task farm on a network of transputers, which still are one of the cleanest and best-balanced building blocks for parallel systems. I report on relevant properties of the basic algorithms the application is comprised of; some relevant details of the task farm software; performance measurements on a range of system sizes for tasks of very different granularity and characteristics (including broadcast of global data) with measured loads on processors and communications links; and the detrimental effects on performance of hardware variants that increase communications latency and reduce available bandwidth. The measurements show that for some of the image processing tasks, the transputer system is `on the edge' with respect to available bandwidth and latency. Some possible improvements to the communications infrastructure are discussed in light of these results. Finally, current approaches to affordable parallel computing, such as networks or clusters of workstations, are put into perspective by comparing them with the transputer system, using computation/communication balance as a figure of merit for the comparison. This shows that for current microprocessors, even their pin bandwidth is not sufficient to sustain equivalent (scaled) performance for this typical image processing application; any multiprocessor system built with current networking hardware is so unbalanced compared to the transputer system that it will be severely limited by communications bandwidth and latency.     

A multi-agent platform for auction-based allocation of loads in transportation logistics

This paper describes an agent-based platform for the allocation of loads in distributed transportation logistics, developed as a collaboration between CWI, Dutch National Center for Mathematics and Computer Science, Amsterdam and Vos Logistics Organizing, Nijmegen, The Netherlands.The platform follows a real business scenario proposed by Vos, and it involves a set of agents bidding for transportation loads to be distributed from a central depot in the Netherlands to different locations across Germany. The platform supports both human agents (i.e. transportation planners), who can bid through specialized planning and bidding interfaces, as well as automated, software agents. We exemplify how the proposed platform can be used to test both the bidding behaviour of human logistics planners, as well as the performance of automated auction bidding strategies, developed for such settings.The paper first introduces the business problem setting and then describes the architecture and main characteristics of our auction platform. We conclude with a preliminary discussion of our experience from a human bidding experiment, involving Vos planners competing for orders both against each other and against some (simple) automated strategies.