  In astrophysics numerical star cluster simulations and hydrodynamical methods
like SPH require computational performance in the petaflop range. The GRAPE
family of ASIC-based accelerators improves the cost-performance ratio compared
to general purpose parallel computers, however with limited flexibility.
  The AHA-GRAPE architecture adds a reconfigurable FPGA-processor to accelerate
the SPH computation. The basic equations of the algorithm consist of three
parts each scaling with the order of O(N), O(N*Nn), and O(N**2) respectively,
where N is in the range of 10**4 to 10**7 and Nn approximately 50. These
equations can profitably be distributed across a host workstation, an FPGA
processor, and a GRAPE subsystem.
  With the new ATLANTIS FPGA processor we expect a scalable SPH performance of
1.5 Gflops per board. The first prototype AHA-GRAPE system will be available in
mid-2000. This 3-layered system will deliver an increase in performance by a
factor of 10 as compared to a pure GRAPE solution.
