An occam Style Communications System for UNIX Networks

This document describes the design of a communications system which provides occam style communications primitives under a Unix environment, using TCP/IP protocols, and any number of other protocols deemed suitable as underlying transport layers. The system will integrate with a low overhead scheduler/kernel without incurring significant costs to the execution of processes within the run time environment. A survey of relevant occam and occam3 features and related research is followed by a look at the Unix and TCP/IP facilities which determine our working constraints, and a description of the T9000 transputer's Virtual Channel Processor, which was instrumental in our formulation. Drawing from the information presented here, a design for the communications system is subsequently proposed. Finally, a preliminary investigation of methods for lightweight access control to shared resources in an environment which does not provide support for critical sections, semaphores, or busy waiting, is made. This is presented with relevance to mutual exclusion problems which arise within the proposed design. Future directions for the evolution of this project are discussed in conclusion

Model-Based Robot Control and Multiprocessor Implementation

Model-based control of robot manipulators has been gaining momentum in recent years. Unfortunately there are very few experimental validations to accompany simulation results and as such majority of conclusions drawn lack the credibility associated with the real control implementation

The Architecture and Programming of a Fine-Grain Multicomputer

The research presented in this thesis was conducted in the context of the Mosaic C, an experimental, fine-grain multicomputer. The objective of the Mosaic experiment was to develop a concurrent-computing system with maximum performance per unit cost, while still retaining a general-purpose application span. A stipulation of the Mosaic project was that the complexity of a Mosaic node be limited by the silicon complexity available on a single VLSI chip. The two most important original results reported in the thesis are: (1) The design and implementation of C+-, a concurrent, object-oriented programming system. Syntactically, C+- is an extension of C++. The concurrent semantics of C+- are contained within the process concept. A C+- process is analogous to a C++ object, but it is also an autonomous computing agent, and a unit of potential concurrency. Atomic single-process updates that can be individually enabled and disabled are the execution units of the concurrent computation. The limited set of primitives that C+- provides is shown to be sufficient to express a variety of concurrent-programming problems concisely and efficiently. An important design requirement for C+- was that efficient implementations should exist on a variety of concurrent architectures, and, in particular, on the simple and inexpensive hardware of the Mosaic node. The Mosaic runtime system was written entirely in C+-. (2) Pipeline synchronization, a novel, generally- applicable technique for hardware synchronization. This technique is a simple, low-cost, high-bandwidth, high- reliability solution to interfaces between synchronous and asynchronous systems, or between synchronous systems operating from different clocks. The technique can sustain the full communication bandwidth and achieve an arbitrarily low, non-zero probability of synchronization failure, Pf, with the price in both latency and chip area being O(log 1/Pf). Pipeline synchronization has been successfully applied to the highperformance inter-computer communication in Mosaic node ensembles