Performance forecasting: towards a methodology for characterizing large computational applications

We present a methodology that can identify and formulate performance characteristics of a computational application and uncover program performance trends on very large, future computer architectures and problem sizes. Based on this methodology we present "performance forecast diagrams" that predict the scalability of a large seismology application suite on a terabyte data set. We find that the applications scale well up to a large number of processors, given an interconnection network similar to the one of the SGI/Cray Origin architecture. However we find that if we increase the computation-to-communication speed ratio by a factor of 100, the different applications of the seismic suite start exhibiting architectural "sweet spots", at which the communication overhead starts to dominate computation time. The presented methodology has proven to be useful in characterizing large computational applications. It is being applied in a project to create a repository of realistic programs and their characteristics.