International Telemetering Conference Proceedings / October 30-November 02, 1995 / Riviera Hotel, Las Vegas, Nevada / The driving force in modern space mission control has been directed towards developing cost effective and reliable communication and data systems. The objective is to maintain and ensure error-free payload commanding and data acquisition as well as efficient processing of the payload data for concurrent, real time and future use. While Mainframe computing still comprises a majority of commercially available communication and data systems, a significant diversion can be noticed towards utilizing a distributed network of workstations and commercially available software and hardware. This motivation reflects advances in modem computer technology and the trend in space mission control today and in the future. The development of communication and data involves the implementation of distributed and parallel processing concepts in a network of highly powerful client server environments. This paper addresses major issues related to developing and integrating communication and data system and the significance for future developments.

Does your program do what it is supposed to be doing? Without running the program providing an answer to this question is much harder if the language does not support static type checking. Of course, even if compile-time checks are in place only certain errors will be detected: compilers can only second-guess the programmer’s intention. But, type based techniques go a long way in assisting programmers to detect errors in their computations earlier on. The question if a program behaves correctly is even harder to answer if the program consists of several parts that execute concurrently and need to communicate with each other. Compilers of standard programming languages are typically unable to infer information about how the parts of a concurrent program interact with each other, especially where explicit threading or message passing techniques are used. Hence, correctness guarantees are often conspicuously absent. Concurrency management in an application is a complex problem. However, it is largely orthogonal to the actual computational functionality that a program realises. Because of this orthogonality, the problem can be considered in isolation. The largest possible separation between concurrency and functionality is achieved if a dedicated language is used for concurrency management, i.e. an additional program manages the concurrent execution and interaction of the computational tasks of the original program. Such an approach does not only help programmers to focus on the core functionality and on the exploitation of concurrency independently, it also allows for a specialised analysis mechanism geared towards concurrency-related properties. This dissertation shows how an approach that completely decouples coordination from computation is a very supportive substrate for inferring static guarantees of the correctness of concurrent programs. Programs are described as streaming networks connecting independent components that implement the computations of the program, where the network describes the dependencies and interactions between components. A coordination program only requires an abstract notion of computation inside the components and may therefore be used as a generic and reusable design pattern for coordination. A type-based inference and checking mechanism analyses such streaming networks and provides comprehensive guarantees of the consistency and behaviour of coordination programs. Concrete implementations of components are deliberately left out of the scope of coordination programs: Components may be implemented in an external language, for example C, to provide the desired computational functionality. Based on this separation, a concise semantic framework allows for step-wise interpretation of coordination programs without requiring concrete implementations of their components. The framework also provides clear guidance for the implementation of the language. One such implementation is presented and hands-on examples demonstrate how the language is used in practice.

With the rapid advances in high-speed network technologies and steady decrease in the cost of hardware involved, network of workstation (NOW) environments began to attract attention as competitors against special purpose, high performance parallel processing environments. NOWs attract attention as parallel and distributed computing environments because they provide high scalability in terms of computing capacity and they have much smaller cost/performance ratios with high availability. However, they are harder to program for parallel and distributed applications because of the issues involved due to their loosely coupled nature. Some of the issues to be considered are the heterogeneity in the software and hardware architectures, uncontrolled external loads, network overheads, frequently changing system characteristics like workload on processors and network links, and security of applications and hosts. The general objective of this work is to provide the design and implementation of a JavaTM-based, high performance and flexible platform i.e. a framework that will facilitate development of wide range of parallel and distributed applications on networks of heterogeneous workstations (NOW). Parallel and distributed application developers are provided an infrastructure (consisting of pieces of executable software developed in Java and a Java software library) that allows them to build and run their distributed applications on their heterogeneous NOW without worrying about the issues specific to the NOW environments. The results of the extensive set of experiments conducted have shown that Safran is quite scaleable and responds well to compute intensive parallel and distributed applications.

This thesis focuses on novel approaches to distributed and parallel computing that are inspired by the mechanism and functioning of biological cells. We refer to this concept as cellular distributed and parallel computing which focuses on three important principles: simplicity, parallelism, and locality. We first give a parallel polynomial-time solution to the constraint satisfaction problem (CSP) based on a theoretical model of cellular distributed and parallel computing, which is known as neural-like P systems (or neural-like membrane systems). We then design a class of simple neural-like P systems to solve the fundamental maximal independent set (MIS) selection problem efficiently in a distributed way, by drawing inspiration from the way that developing cells in the fruit fly become specialised. Building on the novel bio-inspired approach to distributed MIS selection, we propose a new simple randomised algorithm for another fundamental distributed computing problem: the distributed greedy colouring (GC) problem. We then propose an improved distributed MIS selection algorithm that incorporates for the first time another important feature of the biological system: adapting the probabilities used at each node based on local feedback from neighbouring nodes. The improved distributed MIS selection algorithm is again extended to solve the distributed greedy colouring problem. Both improved algorithms are simple and robust and work under very restrictive conditions, moreover, they both achieve state-of-the-art performance in terms of their worst-case time complexity and message complexity. Given any n-node graph with maximum degree Delta, the expected time complexity of our improved distributed MIS selection algorithm is O(log n) and the message complexity per node is O(1). The expected time complexity of our improved distributed greedy colouring algorithm is O(Delta + log n) and the message complexity per node is again O(1). Finally, we provide some experimental results to illustrate the time and message complexity of our proposed algorithms in practice. In particular, we show experimentally that the number of colours used by our distributed greedy colouring algorithms turns out to be optimal or near-optimal for many standard graph colouring benchmarks, so they provide effective simple heuristic approaches to computing a colouring with a small number of colours.

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<p>U radu je predstavljeno istraživanje vezano za poboljšanje performansi rada velikih nadzorno-upravljačkih sistema poput DMS-a. Ovaj cilj je postignut koordinacijom izvršavanja tokova aktivnosti, što podrazumeva efikasnu raspodelu zadataka na računarske resurse. U te svrhe razvijeni su i testirani različiti algoritmi. Ovakav pristup je obezbedio veći stepen iskorišćenja računarskih resursa, što je rezultiralo boljim performansama.</p> / <p>Thе paper presents an approach how to improve performance of larger scale distributed utility management system such as DMS. This goal is accomplished by using an intelligent workflow management. Workflows are divided into the atomic tasks which are scheduled to computing resources for execution. For these purposes various scheduling algorithms are developed and thoroughly tested. This approach has provided greater utilization of computing resources which further have resulted in better performance.</p>