In this paper, we present a proposed system architecture for global computing that we call Atlas, and we describe an early prototype that implements several of the mechanisms and policies that comprise the proposed architecture. Atlas is designed to execute parallel multithreaded programs on the networked computing resources of the world. The Atlas system is a marriage of existing technologies from Java and Cilk together with some new technologies needed to extend the system into the global domain. 1 Introduction The goal of the Atlas system is to exploit the networked resources of the world as a giant distributed computer, and to develop an infrastructure that exploits idle resources both within and among institutions. The Atlas architecture strives for several desirable properties for a global computing infrastructure. Scalability: It must scale to millions of nodes. Heterogeneity: It must include a variety of platforms and operating systems, all of which must interoperate. Faul...

Workstation networks are an underutilized yet valuable resource for solving large-scale parallel problems. In this paper, we present "idle-initiated" techniques for efficiently scheduling large-scale parallel computations on workstation networks. By "idle-initiated," we mean that idle computers actively search out work to do rather than wait for work to be assigned. The idleinitiated scheduler operates at both the macro and the micro levels. On the macro level, a computer without work joins an ongoing parallel computation as a participant. On the micro level, a participant without work "steals" work from some other participant of the same computation. We have implemented these scheduling techniques in Phish, a portable system for running dynamic parallel applications on a network of workstations. 1 Introduction Even with the annual exponential improvements in microprocessor speed, a large body of problems cannot be solved in a reasonable time on a single computer. One method of reduc...

. In this paper we discuss an application of network computing in the area of stochastic simulation. We focus on main programming issues associated with designing of the latest version of AKAROA2, a simulation package in which network computing is applied in a practical and user-friendly way. This implemention is based on Multiple Replications In Parallel (MRIP) scenario of distributed simulation, in which multiple computers of a network operate as concurrent simulation engines generating statistically equivalent simulation output data, and submitting them to global data analysers responsible for analysis of the final results and for stopping the simulation. The MRIP scenario can achieve speedup equal to the number of processors used. Keywords: distributed computing, distributed simulation, stochastic simulation 1 Introduction The number of computer networks, and computers in these networks, has been growing exponentially. This has already led to creation of vast computin...

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Visualization and animation tools may become extremely important aids in the understanding, verification, and performance tuning of parallel computations. Presently, however, the use of visualization has had only a limited use for enhancing parallel computation. We hypothesize that one of the primary reasons for the limited use of visualization tools in parallel program development is the difficulty of acquiring the information necessary to drive the visual display. Our approach to this impediment focuses on integrating visualization support directly into a distributed computing system. Central to this integration is the addition of a logical clock that prevents the timestamps of events from violating causality. The implementation requires the "piggybacking" of a negligible amount of extra header information on system messages and the impact on performance is minimal. This results in a system that produces useful visualizations with no extra effort required by the applications programm...

The purpose of the Xthreads library is to provide a cheap concurrent programming environment. The design of the Xthreads library is patterned after Xinu, a small and elegant operating system in which all processes share a single address space and hence enjoy reduced overheads in process creation, interprocess communication, and so on. Our approach is to map the Xinu process structure into the Xthreads thread structure in a Unix-like process. Easy extensions and modifications to the Xthreads library are a major objective, accomplished through modularity and layering. We have ported Xthreads to the nCUBE2, iPSC860 and RS6000 computers. This paper describes the library, our experiences with its design and implementation, the early performance measurements, and its applicability to simulation modeling. 1 Introduction Lightweight processes are threads of control existing within a single host process, and consequently sharing a single address space. In fundamental structure, a lightweightp...

We present design and implementation strategies for providing general purpose distributed computing primitives on computer networks. This suite of primitives is intended to be a framework within which distributed and concurrent applications may be built in networked environments, in the absence of a distributed operating system. The proposed constructs are derived from typical application requirements, and include group communications, synchronization and recovery, and integrated distributed primitives such as mutual exclusion and consensus. We define an extensible suite of general purpose distributed computing primitives, discuss algorithms for their implementation, and present performance results and experiences. 1. Introduction Distributed applications that execute on networks of computer systems are rapidly increasing in number and variety. Applications that are inherently distributed are evolving, and traditional applications are changing to exploit the many benefits of distribut...

Local or wide-area connected workstation cluster-based computation systems are inherently failure-prone, particularly for long running computations. In this work we introduce a variety of features for failure resilience in the EcliPSe system for replicative applications. Key characteristics of fault-tolerant EcliPSe are ease of use, low statesaving costs, system scalability and good performance. 1 INTRODUCTION Cluster computing, a low-cost alternative to supercomputers, involves the use of workstation clusters to solve compute-intensive problems with solutions that are amenable to distribution [15]. In recent years, this mode of computation has grown to envelop an increasing number of applications, mainly for scientific problems. At the present time, heterogeneous workstation clusters are not ideal replacements for supercomputers, mainly because of their low interconnection bandwidth and reliability. Today's relatively low speed networks and communication protocols, not really design...

Concurrent computing on networked collections of computer systems is rapidly evolving into a viable technology that is attractive from the economic, performance, and availability perspectives. Several software infrastructures that support such heterogeneous network-based concurrent computing have evolved, and are in use for productionquality high-performance computing. In this paper, we describe such a system, and present our experiences with its use for massively concurrent computing in the application domain of polymer physics. The application involves stochastic simulation of polymer chains for measuring scale-invariant phenomena at critical disorder. The parallelization is achieved through the EcliPSe toolkit, and conducted on a flexible, treestructured virtual machine made up of arbitrary and heterogeneous computing nodes dispersed across the country. These nodes cooperate to perform the simulation and pool results together in real time at a central node which initiates the parall...

This paper describes the system, our experiences with its implementation, and its applicability to simulation modeling. We report on performance measurements of different implementations of the simulation scheduler, and of different algorithms for simulating service disciplines