Parallel Hardware Merge Sorter

Sorting has tremendous usage in the applications that handle massive amount of data. Existing techniques accelerate sorting using multiprocessors or GPGPUs where a data set is partitioned into disjunctive subsets to allow multiple sorting threads working in parallel. Hardware sorters implemented in FPGAs have the potential of providing high-speed and low-energy solutions but the partition algorithms used in software systems are so data dependent that they cannot be easily adopted. The speed of most current sequential sorters still hangs around 1 number/cycle. Recently a new hardware merge sorter broke this speed limit by merging a large number of sorted sequences at a speed proportional to the number of sequences. This paper significantly improves its area and speed scalability by allowing stalls and variable sorting rate. A 32-port parallel merge-tree that merges 32 sequences is implemented in a Virtex-7 FPGA. It merges sequences at an average rate of 31.05 number/cycle and reduces the total sorting time by 160 times compared with traditional sequential sorters.