Emerging high-performance applications require the ability to exploit diverse, geographically distributed resources. These applications use high-speed networks to integrate supercomputers, large databases, archival storage devices, advanced visualization devices, and/or scientific instruments to form networked virtual supercomputers or metacomputers. While the physical infrastructure to build such systems is becoming widespread, the heterogeneous and dynamic nature of the metacomputing environment poses new challenges for developers of system software, parallel tools, and applications. In this article, we introduce Globus, a system that we are developing to address these challenges. The Globus system is intended to achieve a vertically integrated treatment of application, middleware, and network. A low-level toolkit provides basic mechanisms such as communication, authentication, network information, and data access. These mechanisms are used to construct various higher-level metacomp...

High-performance execution in distributed computing environments often requires careful selection and configuration not only of computers, networks, and other resources but also of the protocols and algorithms used by applications. Selection and configuration in turn require access to accurate, up-to-date information on the structure and state of available resources. Unfortunately, no standard mechanism exists for organizing or accessing such information. Consequently, different tools and applications adopt ad hoc mechanisms, or they compromise their portability and performance by using default configurations. We propose a solution to this problem: a Metacomputing Directory Service that provides efficient and scalable access to diverse, dynamic, and distributed information about resource structure and state. We define an extensible data model to represent the information required for distributed computing, and we present a scalable, high-performance, distributed implementation. The dat...

While distributed, heterogeneous collections of computers ("Grids") can in principle be used as a computing platform, in practice the problems of first discovering and then configuring resources to meet application requirements are difficult problems. We present a general-purpose resource selection framework that addresses these problems by defining a resource selection service for locating Grid resources that match application requirements. At the heart of this framework is a simple but powerful declarative language based on a technique called set matching, which extends the Condor matchmaking framework to support both single resource and multiple resource selection. This framework also provides an open interface for loading application-specific mapping modules to personalize the resource selector. We present results obtained when this framework is applied in the context of a computational astrophysics application, Cactus. These results demonstrate the effectiveness of our technique.

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In this paper we describe the evolution of grid systems, identifying three generations: first generation systems which were the forerunners of the Grid as we recognise it today; second generation systems with a focus on middleware to support large scale data and computation; and third generation systems where the emphasis shifts to distributed global collaboration, a service oriented approach and information layer issues. In particular, we discuss the relationship between the Grid and the World Wide Web, and suggest that evolving web technologies will provide the basis for the next generation of the Grid. The latter aspect – which we define as the Semantic Grid – is explored in a companion paper. 1.

The coordinated use of geographically distributed computers, or metacomputing, can in principle provide more accessible and cost-effective supercomputing than do conventional highperformance systems. However, we lack evidence that metacomputing systems can be made easily usable or that large numbers of applications are able to exploit metacomputing resources. In this article, we present work that addresses both these concerns. The basis for this work is a system called Nimrod that provides a desktop problemsolving environment for parametric experiments. We describe how Nimrod has been extended to support the scheduling of computational resources located in a wide-area environment and report Proceedings of the 20th Australasian Computer Science Conference, Sydney, Australia, February 5--7 1997. on an experiment in which Nimrod was used to schedule a large parametric study across the Australian Internet. The experiment provided both new scientific results and insights into Nimrod capabi...

We use the term ubiquitous supercomputing to refer to systems that integrate low- and mid-range computing systems, advanced networks, and remote highend computers with the goal of enhancing the computational power accessible from local environments. Such systems promise to enable new applications in areas as diverse as smart instruments and collaborative environments. However, they also demand tools for transporting code between computers and for establishing flexible, dynamic communication structures. In this paper, we propose that these requirements be satisfied by enhancing the Java programming language with global pointer and remote service request mechanisms from a communication library called Nexus. Java supports transportable code; Nexus provides communication support. We explain how this NexusJava library is implemented and illustrate its use with examples. 1 Introduction Rapid advances in networking technologies have made it possible to construct computations that integrate r...

High-speed wide-area networks enable innovative ap-plications that integrate geographically distributed com-puting, database, graphics, and networking resources. The Message Passing Interface (MPI) can be used as a portable, high-performance programming model for such systems. However, the wide-area environment in-troduces challenging problems for the MPI implementor, because of the heterogeneity of both the underlying physical infrastructure and the authentication and software environment at different sites. In this article, we describe an MPI implementation that incorporates so-lutions to these problems. This implementation, which was developed for the I-WAY distributed-computing ex-periment, was constructed by layering MPICH on the Nexus multithreaded runtime system. Nexus provides automatic configuration mechanisms that can be used to select and configure authentication, process creation, and communication mechanisms in heterogeneous systems.

This paper describes an experiment in which a largescale scientific application developed for tightly-coupled parallel machines is adapted to the distributed execution environment of the Information Power Grid (IPG). A brief overview of the IPG and a description of the computational fluid dynamics (CFD) algorithm are given. The Globus metacomputing toolkit is used as the enabling device for the geographically-distributed computation. Modifications related to latency hiding and load balancing were required for an efficient implementation of the CFD application in the IPG environment. Performance results on a pair of SGI Origin2000 machines indicate that real scientific applications can be effectively implemented on the IPG; however, a significant amount of continued effort is required to make such an environment useful and accessible to scientists and engineers. 1.