Software Issues at the User Interface†

We review software issues that are critical to the successful integration of parallel computers into mainstream scientific computing. Clearly a compiler is the most important software tool available to a user on most systems. We discuss compilers from the point of view of communication compilation their ability to generate efficient communication code automatically. We illustrate with two examples of distributed memory computers where almost all communication is handled by the compiler rather than by explicit calls to communication libraries. Closely related to compilation is the need for high quality debuggers. While single node debuggers are important, parallel machines have their own specialized debugging needs related to the complexity of interprocess communication and synchronization. We describe a powerful simulation tool we have developed for such systems and which has proved essential in porting large applications to distributed memory systems. Other important software tools include high level languages, libraries and visualization software. We discuss aspects of these systems briefly. Ultimately however, general purpose supercomputing environments are likely to include more than a single computer system. Parallel computers are often highly specialized, and rarely provide all of the facilities required by a complete application. Over the coming decade we will see the development of heterogeneous environments connecting diverse supercomputers (scalar, vector and parallel) along with high end graphics, disk farms and networking hubs. The real user interface challenge will then be to provide a unified picture of such systems to potential users. hhhhhhhhhhhhhhhh † Presented at Frontiers of Supercomputing II: A National Reassesessment, Los Alamos National Laboratory, August 1990. * Research supported by the Air Force Office of Scientific Research, under grant AFOSR-89-0422