Distributed Computing

Distributed computing is an important challenge because supercomputers are no longer isolated systems. The typical supercomputer installation contains dozens of systems, including front ends, fileservers, workstations, and other supercomputers. Distributed computing encompasses all of the problems encountered in convincing these systems to work together in a cooperative fashion. This is a long-standing research area in computer science but is of increasing importance because of greater functional specialization in supercomputing environments.

Functional specialization is a key driving force in the evolution of supercomputing environments. The defining characteristic of such environments is that the specialization of hardware is reflected in the structure of applications. Ideally, applications are divided into components that execute on the most appropriate hardware. This reserves the supercomputer for the components of the application that truly need its high performance and allows other components to execute elsewhere (e.g., a researcher's workstation, a graphics display unit, etc.). Cooperation and coordination among these components is of paramount importance to the successful use of such environments. A related challenge is that of partitioning problems into appropriate components. Communication costs are an important consideration in this regard, as higher costs require a coarser degree of interaction among the components.

Transparency and interoperability are key system characteristics that are required in such environments. Transparent communication mechanisms work in the same fashion, independent of the location of the communicating

components, including whether the communication is local to a single machine. Interoperability ensures that communication mechanisms function correctly among different types of hardware from different manufacturers, which is exactly the situation in current supercomputing environments. Achieving these goals is not easy but is a basic requirement for systems software that supports functionally specialized supercomputing environments.