Distributed high-performance computing---so-called metacomputing---refers to the coordinated use of a pool of geographically distributed high-performance computers. The user's view of an ideal metacomputer is that of a powerful monolithic virtual machine. The implementor 's view, on the other hand, is that of a variety of interacting services implemented in a scalable and extensible manner. In this paper, we present MOL, the Metacomputer Online environment. In contrast to other metcomputing environments, MOL is not based on specific programming models or tools. It has rather been designed as an open, extensible software system comprising a variety of software modules, each of them specialized in serving one specific task such as resource scheduling, job control, task communication, task migration, user interface, and much more. All of these modules exist and are working. The main challenge in the design of MOL lies in the specification of suitable, generic interfaces for the effective ...

This paper describes a tool for the development of distributed applications. The target execution environment is a network of heterogenous general-purpose workstations. This tool (called HERMES) mainly handles the message transport layer and does not deal with aspects more directly related to parallel computing, such as the topology of communicating processes or load balancing among processors. A coarse-grained concurrence is supported and the resulting parallel architecture is based on the multiple-instructions multiple-data paradigm. This system is mainly characterized by its ability of handling special messages (alarm and urgent) that are guaranteed immediate processing by the receiving process. Messages are always asynchronous, in that they are immediately delivered to destination, without any temporary buffering by the communication system (i.e. asynchronously with respect to the program execution). The system is still under development but a preliminary version, restricted to pro...