A case for energy-efficient acceleration of graph problems using embedded FPGA-based SoCs

Sparse graph problems are notoriously hard to accelerate on conventional platforms due to irregular memory access patterns resulting in underutilization of memory bandwidth. These bottlenecks on traditional x86-based systems mean that sparse graph problems scale very poorly, both in terms of performance and power efficiency. A cluster of embedded SoCs (systems-on-chip) with closely-coupled FPGA accelerators can support distributed memory accesses with better matched low-power processing. We first conduct preliminary experiments across a range of COTS (commercial off-the-shelf) embedded SoCs to establish promise for energy-efficiency acceleration of sparse problems. We select the Xilinx Zynq SoC with FPGA accelerators to construct a prototype 32-node Beowulf cluster. We develop specialized MPI routines and memory DMA offload engines to support irregular communication efficiently. In this setup, we use the ARM processor as a data marshaller for local DMA traffic as well as remote MPI traffic while the FPGA may be used as a programmable accelerator. Across a set of benchmark graphs, we show that 32-node embedded SoC cluster can exceed the energy efficiency of an Intel E5-2407 by as much as 1.7× at a total graph processing capacity of 91–95 MTEPS for graphs as large as 32 million nodes and edges.Published versio