1Scalable Interaction with Parallel Applications

Abstract—A range of tools, from parallel debuggers to per-formance analysis/visualization to simulation visualizers, can benefit from interaction with a running parallel application. To be effective, this live interaction needs to be highly scal-able. Such scalability for parallel applications is available in the form of the Charm++/AMPI runtime system. Charm++ is an object-based, message-driven model of parallel program-ming that has enabled high levels of scalability for complex applications like NAMD, a production bio-molecular simula-tion code frequently used on Teragrid systems. External tools may communicate via a socket connection with an executing parallel Charm++ application through our Converse Client-Server (CCS) interface and framework. We demonstrate var-ious tools that exploit the scalable properties of Charm++’s adaptive runtime to intersperse interaction activity and com-munication with the running application’s work. We show how this allows tools to interact effectively and scalably with parallel applications running on thousands of processors. I