LU is a blocked LU factorization of a dense matrix. The processors are organized in a grid. The communication volume is low, and is along rows and columns of the processor grid. MP3D is our communication stress test. The communication volume is large, and the communication patterns are very unstructured and are read-write in nature.
Ocean is a regular grid nearest-neighbor application with a multigrid solver.
Every processor is assigned a square subgrid of every grid, and traverses its subgrid communicating with its neighbors at the boundaries. The important working set is simply the size of a processor's partition of a grid, and the working sets are disjoint. Radix is a sorting kernel that sorts a large number of integers. The communication phase is composed of processors using the values of their keys to write these keys into random locations in a shared array that is distributed among the processors. Raytrace and Volrend are applications from computer graphics.