Opus is a new programming language designed to assist in coordinating the execution of multiple, independent program modules. With the help of Opus, coarse grained task parallelism between data parallel modules can be expressed in a clean and structured way. In this paper we address the problems of how to build a compilation and runtime support system that can efficiently implement the Opus constructs. Our design considers the often-conflicting goals of efficiency and modular construction through software re-use. In particular, we present the system requirements for an efficient Opus implementation, the Opus runtime system, and describe how they work together to provide the underlying services that the Opus compiler needs for a broad class of machines. Copyright © 2000 John Wiley & Sons, Ltd.

Open Implementation Analysis and Design (OIA/D) has been introduced as a design methodology for object-oriented software systems, and in particular for substrate software. In this paper we detail our experiences with using OIA/D to design and implement a common substrate component for parallel language runtime systems: a lightweight threads package. We show how existing thread packages employ a "black-box" design, hiding crucial design decisions that drastically reduce their ability to be re-used. We detail these design decisions (dilemmas) and show how an implementation based on OIA/D principles results in a thread package that is flexible, efficient, portable, and re-usable.

Threads provide a useful programming model for asynchronous behavior because of their ability to encapsulate units of work that can then be scheduled for execution at runtime, based on the dynamic state of a system.Recently, the threaded model has been applied to the domain of data parallel scientific codes, and initial reports indicate that the threaded model can produce performance gains over non-threaded approaches, primarily through the use of overlapping useful computation with communicant ion latency.However, overlapping computation with communication is possible without the benefit of threads if the communication system supports asynchronous primitives, and this comparison has not been made in previous papers.This paper provides a critical look at the utility of lightweight threads as applied to data parallel scientific programming.

Data files for scientific and engineering codes typically consist of a series of raw data values whose description is buried in the programs that interact with these files. In this situation, making even minor changes in the file structure or sharing files between programs (interoperability) can only be done after careful examination of the data files and the I/O statements of the programs interacting with this file. In short, scientific data files lack self-description, and other self-describing data techniques are not always appropriate or useful for scientific data files. By applying an object-oriented methodology to data files, we can add the intelligence required to improve data interoperability and provide an elegant mechanism for supporting complex, evolving, or multidisciplinary applications, while still supporting legacy codes. As a result, scientists and engineers should be able to share datasets with far greater ease, simplifying multidisciplinary applications and greatly facilitating remote collaboration between scientists.

Lightweight threads are becoming increasingly useful for supporting parallelism and asynchronous control structures in applications and language implementations. However, lightweight thread packages for distributed memory systems have received little attention. We introduce the design of a runtime interface, called Chant, that supports communicating threads in a distributed memory environment. In particular, Chant is layered atop standard message passing and lightweight thread libraries, and supports efficient point-to-point and remote service request communication primitives. We examine the design issues of Chant, the efficiency of its point-to-point communication layer, and the evaluation of scheduling policies to poll for the presence of incoming messages.>