A General Framework for Complex Time-Driven Simulations on Hypercubes

Abstract

We describe a general framework for building and running complex time-driven simulations with several levels of concurrency. The framework has been implemented on the Caltech/JPL Mark IIIfp hypercube using the Centaur communications protocol. Our framework allows the programmer to break the hypercube up into one or more subcubes of arbitrary size (task parallelism). Each subcube runs a separate application using data parallelism and synchronous communications internal to the subcube. Communications between subcubes are performed with asynchronous messages. Subcubes can each define their own parameters and commands which drive their particular application. These are collected and organized by the Control Processor (CP) in order that the entire simulation can be driven from a single command-driven shell. This system allows several programmers to develop disjoint pieces of a large simulation in parallel and to then integrate them with little effort. Each programmer is, of course, also able to take advantage of the separate data and I/O processors on each hypercube node in order to overlap calculation and communication (on-board parallelism) as well as the pipelined floating point processor on each node (pipelined processor parallelism). We show, as an example of the framework, a large space defense simulation. Functions (sensing, tracking, etc.) each comprise a subcube; functions are collected into defense platforms (satellites); and many platforms comprise the defense architecture. Software in the CP uses simple input to determine the node allocation to each function based on the desired defense architecture and number of platforms simulated in the hypercube. This allows many different architectures to be simulated. The set of simulated platforms, the results, and the messages between them are shown on color graphics displays. The methods used herein can be generalized to other simulations of a similar nature in a straightforward manner.