Visualizing the behavior of massively parallel programs

Abstract

Programs for massively parallel SIMD computers are difficult to write, understand, and debug -much more so than serial programs running on a conven­ tional computer. The barriers to understanding and debugging SIMD programs may be lowered by graph­ ically visualizing these programs as they execute. This paper describes a conceptual framework for monitoring the execution of SIMD programs in a non­ invasive fashion, and characterizes the user-interaction paradigm of a novel computer-aided design system for creating new visualizations. These ideas, and the im­ portance of visualization for SIMD programming and debugging, are illustrated in an actual debugging sce­ nario that was recorded during the use of the Inte­ grated Visualization Environment (IVE), a prototype system being developed at Harvard University and the Lockheed Palo Alto Research Labs., Advanced Com­ putation Lab.