This paper addresses the design of reactive real-time embedded systems. Such systems are often heterogeneous in implementation technologies and design styles, for example by combining hardware ASICs with embedded software. The concurrent design process for such embedded systems involves solving the specification, validation, and synthesis problems. We review the variety of approaches to these problems that have been taken.

terests include parallel programming environments for distributed memory applications. He received an MS (in 1992) and a BS (in 1991) in computing science from the University of Alberta, and a BS in chemistry from the University of Western Ontario in 1978. Greg Lobe is works for Bell Northern Research in Ottawa. His research interests include object-oriented and parallel programming. He received his MS and BS in computing science from the University of Alberta in 1993 and 1989 respectively. 2 This is a pre-print of a copyrighted article in IEEE Parallel and Distributed Technology, vol. 1, no. 3, August 1993. Introduction Designing, implementing, and testing distributed software is considerably more difficult than for comparable sequential software. There are efficient parallel algorithms for a large class of problems, but finding the right one can be only a small part of the implementation cost. Writing distributed software is also complicated by pro

This paper presents Jade, a language which allows a programmer to easily express dynamic coarse-grain parallelism. Starting with a sequential program, a programmer augments those sections of code to be parallelized with abstract data usage information. The compiler and run-time system use this information to concurrently execute the program while respecting the program's data dependence constraints. Using Jade can significantly reduce the time and effort required to develop and maintain a parallel version of an imperative application with serial semantics. The paper introduces the basic principles of the language, compares Jade with other existing languages, and presents the performance of a sparse matrix Cholesky factorization algorithm implemented in Jade.

In the near future, most objects of common use will contain electronics to augment their functionality, performance, and safety. Hence, time-tomarket, safety, low-cost, and reliability will have to be addressed by any system design methodology. A fundamental aspect of system design is the specification process. We advocate using an unambiguous formalism to represent design specifications and design choices. This facilitates tremendously efficiency of specification, formal verification, and correct design refinement, optimization, and implementation. This formalism is often called model of computation. There are several models of computation that have been used, but there is a lack of consensus among researchers and practitioners on the "right" models to use. To the best of our knowledge, there has also been little effort in trying to compare rigorously these models of computation. In this paper, we review current models of computation and compare them within a framework that has been r...

This paper relates to system-level design of signal processing systems, which are often heterogeneous in implementation technologies and design styles. The heterogeneous approach, by combining small, specialized models of computation, achieves generality and also lends itself to automatic synthesis and formal verification. Key to the heterogeneous approach is to define interaction semantics that resolve the ambiguities when different models of computation are brought together. For this purpose, we introduce a tagged signal model as a formal framework within which the models of computation can be precisely described and unambiguously differentiated, and their interactions can be understood. In this paper, we will focus on the interaction between dataflow models, which have partially ordered events, and discrete-event models, with their notion of time that usually defines a total order of events. A variety of interaction semantics, mainly in handling the different notions of time in the two models, are explored to illustrate the subtleties involved. An implementation based on the Ptolemy system from U.C. Berkeley is described and critiqued.

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this paper we introduce MANIFOLD:

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By viewing different parallel programming paradigms as essential heterogeneous approaches in mapping "real-world" problems to parallel systems, we discuss methodologies in integrating multiple programming models on a Connection Machine CM5. In a data flow based integration model built in a visualization software AVS, we demonstrate a simple, effective and modular way to couple sequential, data-parallel and explicit message-passing modules into an integrated programming environment onthe CM5.

Workstation environments have been in use for more than a decade now. Although a network of workstations together represents a large amount of aggregate computing power, single users often cannot utilize these resources for their applications. Enterprise is a programming environment for designing, coding, debugging, testing, monitoring, profiling and executing programs in a distributed hardware environment. Enterprise code looks like familiar sequential code; the parallelism is expressed graphically. The system automatically inserts the code necessary to handle communication, synchronization and fault tolerance, allowing the rapid construction of correct distributed programs. Enterprise programs run on a network of computers, absorbing the idle cycles on machines. The system supports load balancing, limited process migration, and dynamic distribution of work in environments with changing resource utilization. Enterprise offers a costeffective method for increasing the productivity of p...