A HIGHLY PARALLELIZED SPECIAL-PURPOSE COMPUTER FOR MANY-BODY SIMULATIONS WITH AN ARBITRARY CENTRAL FORCE: MD-GRAPE

摘要

We have developed a parallel, pipelined special-purpose computer for N-body simulations, MD-GRAPE (for " GRAvity PipE "). In gravitational N-body simulations, almost all computing time is spent on the calculation of interactions between particles. GRAPE is specialized hardware to calculate these interactions. It is used with a general-purpose front-end computer that performs all calculations other than the force calculation. MD-GRAPE is the first parallel GRAPE that can calculate an arbitrary central force. A force different from a pure 1/r potential is necessary for N-body simulations with periodic boundary conditions using the Ewald or particle-particle/particle-mesh (P~3M) method. MD-GRAPE accelerates the calculation of particle-particle force for these algorithms. An MD-GRAPE board has four MD chips and its peak performance is 4.2 GFLOPS. On an MD-GRAPE board, a cosmological N-body simulation takes 600(N/10~6)~(3/2) s per step for the Ewald method, where N is the number of particles, and would take 240(N/10~6) s per step for the P~3M method, in a uniform distribution of particles.