Parallel computing on local area networks is generally based on mechanisms that specifically target the properties of the local area network environment. However, these mechanisms do not effectively extend to wide area networks due to issues such as heterogeneity, security, and administrative boundaries. We present a system which enables application programmers to write parallel programs in Java and allows Java-capable browsers to execute parallel tasks. It comprises a virtual machine model which isolates the program from the execution environment, and a runtime system realizing this virtual machine on the Web. Load balancing and fault masking are transparently provided by the runtime system.

Java, in combination with Web browsers' abilities to load and execute untrusted Java applets in a secure fashion, has made computing over the Web a possibility. Now the challenge is to fully utilize this potential, given the limitations imposed by browsers. This paper presents KnittingFactory, an infrastructure to facilitate Web-based computing, which addresses this challenge. It supports building distributed applications, specifically those consisting of Java applets executing in browsers. It is composed of: (i) a distributed name service to assist users in locating other participants of a distributed computation via standard browsers; (ii) an embedded class server to eliminate the need for external HTTP servers for serving applet code; and (iii) a technique for direct applet-to-applet communication. In this paper, we describe the design and implementation of KnittingFactory and demonstrate its benefits by applying it to three distinct areas of Web-based computing. First, we apply our distributed name service to a client/server architecture to enable RMI clients to locate servers on unknown hosts. Second, we use the embedded class server to extend the capability of Charlotte, a parallel computing environment. Finally, we build a collaborative application using our direct applet-to-applet communication technique which does not require a forwarding agent. © 1998 John Wiley & Sons, Ltd.

The importance of adapting networks of workstations for use as parallel processing platforms is well established. However current solutions do not always address important issues that exist in real networks. External factors like the sharing of resources, unpredictable behavior of the network and failures, are present in multiuser networks and must be addressed. CALYPSO is a prototype software system for writing and executing parallel programs on non-dedicated platforms, based on COTS networked workstations operating systems, and compilers. Among notable properties of the system are: (1) simple programming paradigm incorporating shared memory constructs and separating the programming and the execution parallelism, (2) transparent utilization of unreliable shared resources by providing dynamic load balancing and fault tolerance, and (3) effective performance for large classes of coarse-grained computations. We present the system and report our initial experiments and performance results in settings that closely resemble the dynamic behavior of a "real" network. Under varying work-load conditions, resource availability and process failures, the efficiency of the test program we present ranged from 84% to 94% bench-marked against a sequential program.