Constructing scientific applications from heterogeneous resources.

Abstract

The computer simulation of scientific processes is playing an increasingly important role in scientific research. For example, the development of adequate flight simulation environments, numeric wind tunnels, and numeric propulsion systems is reducing the danger and expense involved in prototyping new aircraft and engine designs. One serious problem that hinders the full realization of the potential of scientific simulation is the lack of tools and techniques for dealing with the heterogeneity inherent in today's computational resources and applications. Typically, either ad hoc connection techniques, such as manual file transfer between machines, or approximation techniques, such as boundary value equations, are employed. This dissertation develops a programming model in which scientific applications are designed as heterogeneous distributed programs, or meta-computations. The central feature of the model is an interconnection system that handles the transfer of control and data among the heterogeneous components of the meta-computation, and provides configuration tools to assist the user in starting and controlling the distributed computation. Key benefits of this programming model include the ability to simulate the interactions among the physical processes being modeled through the free exchange of data between computational components. Another benefit is the possibility of improved user interaction with the meta-computation, allowing the monitoring of intermediate results during long simulations and the ability to steer the simulation, either directly by the user or through the incorporation of an expert system into the meta-computation. This dissertation describes a specific realization of this model in the Schooner interconnection system, and its use in the construction of a number of scientific meta-computations. Schooner uses a type specification language and an application-level remote procedure call mechanism to ease the task of the scientific programmer in building meta-computations. It also provides static and dynamic configuration management features that support the creation of meta-computations from components at runtime, and their modification during execution. Meta-computations constructed using Schooner include examples involving molecular dynamics and neural nets. Schooner is also in use in several major projects as part of a NASA effort to develop improved jet engine simulations.