PROGRAPE-1: A Programmable, Multi-Purpose Computer for Many-Body Simulations

We have developed PROGRAPE-1 (PROgrammable GRAPE-1), a programmable multi-purpose computer for many-body simulations. The main difference between PROGRAPE-1 and ``traditional'' GRAPE systems is that the former uses FPGA (Field Programmable Gate Array) chips as the processing elements, while the latter relies on a hardwired pipeline processor specialized to gravitational interactions. Since the logic implemented in FPGA chips can be reconfigured, we can use PROGRAPE-1 to calculate not only gravitational interactions, but also other forms of interactions, such as the van der Waals force, hydro\-dynamical interactions in the SPHr calculation, and so on. PROGRAPE-1 comprises two Altera EPF10K100 FPGA chips, each of which contains nominally 100000 gates. To evaluate the programmability and performance of PROGRAPE-1, we implemented a pipeline for gravitational interactions similar to that of GRAPE-3. One pipeline is fitted into a single FPGA chip, operated at 16 MHz clock. Thus, for gravitational interactions, PROGRAPE-1 provided a speed of 0.96 Gflops-equivalent. PROGRAPE will prove to be useful for a wide-range of particle-based simulations in which the calculation cost of interactions other than gravity is high, such as the evaluation of SPH interactions.