Abstract not found

Recent results in the application of... this paper. The review takes the form of an analysis of the problems presented by different application requirements and characteristics. Issues covered include uniprocessor and multiprocessor systems, periodic and aperiodic processes, static and dynamic algorithms, transient overloads and resource usage. Protocols that limit and reduce blocking are discussed. Considerations are also given to scheduling Ada tasks.

A multiparty interaction is a set of I/O actions executed jointly by a number of processes, each of which must be ready to execute its own action for any of the actions in the set to occur. An attempt to participate in an interaction delays a process until all other participants are available. Although a relatively new concept, the multiparty interaction has found its way into a number of distributed programming languages and algebraic models of concurrency. In this paper, we present a taxonomy of languages for multiparty interaction that covers all proposals of which we are aware. Based on this taxonomy, we then present a comprehensive analysis of the computational complexity of the multiparty interaction scheduling problem, the problem of scheduling multiparty interactions in a given execution environment. 1 Introduction A multiparty interaction is a set of I/O actions executed jointly by a number of processes, each of which must be ready to execute its own action for any of the act...

A first-order multiparty interaction is an abstraction mechanism that defines communication among a set of formal process roles. Actual processes participate in a first-order interaction by enroling into roles, and execution of the interaction can proceed when all roles are filled by distinct processes. As in CSP, enrolement statements can serve as guards in alternative commands. The enrolement guard scheduling problem then is to enable the execution of first-order interactions through the judicious scheduling of roles to processes currently ready to execute enrolement guards. We present a fully distributed and message-efficient algorithm for the enrolement guard scheduling problem, the first such solution of which we are aware. We also describe several extensions of the algorithm, including generic roles, dynamically changing environments where processes can be created and destroyed at run time, and nested-enrolement which allows interactions to be nested.

A programming language can provide much better support for interprocess communication than a library package can. Most message-passing languages limit this support to communication between the pieces of a single program, but this need not be the case. Lynx facilitates convenient, typesafe message passing not only within applications, but also between applications, and among distributed collections of servers. Specifically, it addresses issues of compiler statelessness, late binding, and protection that allow run-time interaction between processes that were developed independently and that do not trust each other. Implementation experience with Lynx has yielded important insights into the relationship between distributed operating systems and language run-time support packages, and into the inherent costs of high-level message-passing semantics. Keywords: Distributed programming languages, message passing, remote procedure call, late binding, server processes, links. 1. Introduction A...

This paper introduces the newest version of the SR concurrent programming language and illustrates how it provides support for different execution environments, ranging from shared-memory multiprocessors to distributed systems. SR uses a few well-integrated mechanisms for concurrency to provide flexible, yet efficient, support for parallel and distributed programming. This paper gives several realistic examples to illustrate these language mechanisms. 1. Introduction The SR concurrent programming language has been around, in one form or another, for over ten years. The earliest version, now called SR 0 , contained mechanisms for asynchronous message passing and rendezvous [Andr81,Andr82]. Its form of rendezvous, unique at the time, provided a means by which the process servicing a rendezvous could choose which invocation to service based on the values of invocation parameters. Experience using SR 0 substantiated the general appropriateness of the language, but also pointed out se...

Abstract not found

Programmable logic devices (PLDs) are increasing in complexity and speed, and are being used as important components in safety-critical systems. Methods for developing high-integrity software for these systems are well-known, but this is not true for programmable logic. We propose a process for developing a system incorporating software and PLDs, suitable for safety critical systems of the highest levels of integrity. This process incorporates the use of Synchronous Receptive Process Theory as a semantic basis for specifying and proving properties of programs executing on PLDs, and extends the use of SPARK Ada from a programming language for safety-critical systems software to cover the interface between software and programmable logic. We have validated this approach through the specification and development of a substantial safety-critical system incorporating both software and programmable logic components, and the development of tools to support this work. This enables us to claim that the methods demonstrated are not only feasible but also scale up to realistic system sizes, allowing development of such safety-critical software-hardware systems to the levels required by current system safety standards. Declaration of originality I declare that no part of this work has previously been submitted to a university or other educational institution for a degree or other qualification. I further declare that this thesis is my original work, except for clearly indicated sections where the appropriate attributions and acknowledgements are given to work by other authors.

We present two randomized algorithms, one for message passing and the other for shared memory, that, with probability 1, schedule multiparty interactions in a strongly fair manner. Both algorithms improve upon a previous result by Joung and Smolka (proposed in a shared-memory model, along with a straightforward conversion to the message-passing paradigm) in the following aspects: First, processes' speeds as well as communication delays need not be bounded by any predetermined constant. Secondly, our algorithms are completely decentralized, and the sharedmemory solution makes use of only single-writer variables. Finally, both algorithms are symmetric in the sense that all processes execute the same code, and no unique identifiers are used to distinguish processes. 1 Introduction Since Hoare introduced CSP [13], interactions and nondeterminism have become two fundamental features in many programming languages for distributed computing (e.g., Ada [34], Script [11], Action Systems [3], IP ...

: Two important aspects of developing a real-time system are controlling devices and managing concurrency. In this report, we present several techniques for controlling devices with Ada and several Ada tasking paradigms for managing concurrency. The material presented in this report is taken from our experiences in developing a real-time embedded system in Ada, and we use examples from this system to illustrate the various methods we present. We begin by describing our experiences using Ada to control devices. Specifically, we identify issues related to accessing device registers and handling interrupts, and present techniques for dealing with such issues. We then recount our experiences using Ada to manage concurrency. Specifically, we present coding paradigms for implementing periodicity and constructing synchronization mechanisms. We illustrate analytical methods for determining the schedulability of a task set. We then discuss the effect of aperiodic processing requirements on the ...