Methodologies in development and testing of the dataflow machine EM-4

Abstract

The EM-4 is a highly parallel dataflow machine whose target structure will have more than a thousand processing elements (PEs), and a prototype system with 80PEs has been in operation since April 1990 (peak performance 1 Gips). In this paper, the methodologies in development and testing of the EM-4 prototype are described. Development of a dataflow machinne has been often seriously hard, since its architecture is not suited for effective debugging. In the EM-4 prototype, however, a systematic development and testing was made possible through the introduction of (1) a maintenance architecture for efficient debugging, and (2) a testbed system for individual testing of isolated PE boards. The reliability was gradually extended over a wide area of the system (including the software), using an incremental testing method that is also presented in this paper. In addition, a system debugging environment with a software simulator, a stepper, and a tracer, was developed. The EM-4 prototype is also equipped with an improved operating environment that includes the programning environment, troubleshooting method, and performance measuring method.