GRAPE 4: a one-Tflops special-purpose computer for astrophysical N-body problem

We describe the GRAPE-4 (Gravity Pipe 4) system, a special-purpose computer for astrophysical N-body simulations. In N-body simulations, most of the computing time is spent to calculate the force between particles, since the number of interactions is proportional to the square of the number of particles. For many problems the accuracy of fast algorithms such as the particle-mesh scheme is not sufficient and we have to use the straightforward direct summation. In order to accelerate the force calculation, we have developed a series of hardware, the GRAPE (Gravity Pipe) systems. The basic idea of our GRAPE systems is to develop a hardware specialized for the force calculation. The rest of the calculation is performed on the general-purpose computer connected to GRAPE. The GRAPE-4 system is our newest hardware, scheduled to be completed in early 1995. Planned peak speed is 1.15 Tflops. This speed is achieved by running 1920 pipeline LSIs, each provides 600 Mflops, in parallel. A prototype system has been completed July 1994, and the full system is now under manufacturing