Reduction calculator in an FPGA based switching Hub for high performance clusters

Unused logic in the field-programmable gate array (FPGA) for the switching hub is one potential resource to accelerate the computation of data exchanged through the hub. However, for large scale scientific computation, it is difficult to implement such an accelerator on the FPGA used in high performance computers. Here, a reduction calculator for executing ARGOT (accelerated radiative transfer on grids using oct-tree) to solve the radiative transfer equation used for simulation of astronomical objects is implemented on the FPGA of PEACH2 (PCI Express Adaptive Communication Hub ver2), a low latency switching hub for high performance GPU (graphics processor unit) clusters. The implemented reduction calculator uses a pipelined tree of adders and works with a 150-MHz clock without affecting the switching hub functions. Use of the DMA (direct memory access) transfer with descriptors made it possible to improve the performance of CPU excution by a maximum of about 45 times in a real system.