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

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 calculati on 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 calc ulation. MO-GRAPE is the first parallel GRAPE that can calculate an ar bitrary central force. A force different from a pure 1/r potential is necessary for N-body simulations with periodic boundary conditions usi ng the Ewald or particle-particle/particle-mesh (P(3)M) method. MO-GRA PE accelerates the calculation of particle-particle force for these al gorithms. An MO-GRAPE board has four MD chips and its peak performance is 4.2 GFLOPS. On an MO-GRAPE board, a cosmological N-body simulation takes 600(N/10(6))(3/2) s per step for the Ewald method, where N is t he number of particles, and would take 240(N/10(6)) s per step for the P(3)M method, in a uniform distribution of particles.