POLYSHIFT Communications Software for the Connection Machine System CM-200

We describe the use and implementation of a polyshift function PSHIFT for circular shifts and end{oo shifts. Polyshift is useful in many scientiic codes using regular grids, such as nite diierence codes in several dimensions, multigrid codes, molecular dynamics computations, and in lattice gauge physics computations , such as Quantum Chromodynamics (QCD) calculations. Our implementation of the PSHIFT function on the Connection Machine systems CM{2 and CM{200 ooers a speedup of up to a factor of 3{4 compared to CSHIFT when the local data motion within a node is small. The PSHIFT routine is included in the Connection Machine Scientiic Software Library (CMSSL).