In-network stable radix sorter using many FPGAs with high-bandwidth photonics [Invited]

A modern field-programmable gate array (FPGA) card can be equipped with high-bandwidth memory and high-bandwidth optical interconnection networks. This paper presents an in-network stable radix sorter on an eight-FPGA cluster. Each custom Stratix10 MX2100 FPGA card has up to 819-Gbps memory bandwidth (<tex>${51.2}\;{\rm Gbps} \times {16}\;{\rm channels}$</tex>) and up to 800-Gbps network bandwidth (<tex>${25}\;{\rm Gbps} \times {32}\;{\rm channels}$</tex>) with eight custom embedded optical modules. Our radix sorter for a 32-bit key range consists of eight 4-bit counting sorts optimized to in-network processing. Each counting sort needs only one memory read/write access for improving its throughput. We demonstrated a sorting throughput of 37.2 GB/s and an energy efficiency of 9.2 MB/J for 32-bit key range and 16-GiB data size using eight memory channels with 409.6 Gbps memory bandwidth per FPGA. It can scale up to 256 FPGAs with a sorting throughput of 983 GB/s for a 32-bit key range and 512-GiB data size.