Embodiments include methods, systems and computer program products for performing a tournament tree sort on a hardware accelerator having an external memory. The method includes receiving a plurality of key values by the hardware accelerator, assigning each of the plurality of key values a sequential key number as the plurality of key values are received and performing pairwise comparisons of each of the plurality of key values to identify a winning key and a losing key. The method also includes storing the losing key of each pairwise comparison in a first section of the external memory, wherein a location in the first section is based on the key number of the losing key and storing the winning key of each pairwise comparison in a second section of the external memory, wherein a location in the second section is based on the key number of the winning key.