Accelerating solvers for global atmospheric equations through mixed-precision data flow engine

One of the most essential and challenging components in a climate system model is the atmospheric model. To solve the multi-physical atmospheric equations, developers have to face extremely complex stencil kernels. In this paper, we propose a hybrid CPU-FPGA algorithm that applies single and multiple FPGAs to compute the upwind stencil for the global shallow water equations. Through mixed-precision arithmetic, we manage to build a fully pipelined upwind stencil design on a single FPGA, which can perform 428 floating-point and 235 fixed-point operations per cycle. The CPU-FPGA algorithm using one Virtex-6 FPGA provides 100 times speedup over a 6-core CPU and 4 times speedup over a hybrid node with 12 CPU cores and a Fermi GPU card. The algorithm using four FPGAs provides 330 times speedup over a 6-core CPU; it is also 14 times faster and 9 times more power efficient than the hybrid CPU-GPU node.