Toward Scalable Performance Visualization with Jumpshot. Jumpshot is a graphical tool for understanding the performance of parallel programs. It is in the tradition of the upshot tool, but contains a number of extensions and enhancements that make it suitable for large-scale parallel computations. Jumpshot takes as input a new, more flexible logfile format, and comes with a library for generating such logfiles. An MPI profiling library is also included, enabling the automatic generation of such logfiles from MPI programs. Jumpshot is written in Java, and can easily be integrated as an applet into browser-based computing environments. The most novel feature of Jumpshot is its automatic detection of anomalous durations, drawing the user’s attention to problem areas in a parallel execution. This capability is particularly useful in large-scale parallel computations containing very many events.