Falcon: On-line Monitoring for Steering Parallel Programs 1

Advances in high performance computing, communications, and user interfaces enable developers to construct increasingly interactive high performance applications. The Falcon system presented in this paper supports such interactivity by providing runtime libraries, tools, and user interfaces that permit the on-line monitoring and steering of large-scale parallel codes. The principal aspects of Falcon described in this paper are its abstractions and tools for capture and analysis of application-speci c program information, performed on-line, with controlled latencies and scalable to parallel machines of substantial size. In addition, Falcon provides support for the on-line graphical display of monitoring information, and it allows programs to be steered during their execution, by human users or algorithmically. This paper presents our basic research motivation, outlines the Falcon system's functionality, and includes a detailed evaluation of its performance characteristics in light of its principal contributions. Falcon's functionality and performance evaluation are driven by our experiences with large-scale parallel applications being developed with end users in physics and in atmospheric sciences. The sample application highlighted in this paper is a molecular dynamics simulation program (MD) used by physicists to study the statistical mechanics of liquids. Index Terms { Parallel processing, program steering, program adaptation, on-line monitoring, instrumentation, trace analysis, perturbation, performance evaluation, performance displays, molecular dynamics simulation.