Induced Sorting Suffixes in External Memory

We present in this article an external memory algorithm, called disk SA-IS (DSA-IS), to exactly emulate the induced sorting algorithm SA-IS previously proposed for sorting suffixes in RAM. DSA-IS is a new disk-friendly method for sequentially retrieving the preceding character of a sorted suffix to induce the order of the preceding suffix. For a size n string of a constant or integer alphabet, given the RAM capacity Ω (( nW ) 0.5 ), where W is the size of each I/O buffer that is large enough to amortize the overhead of each access to disk, both the CPU time and peak disk use of DSA-IS are O ( n ). Our experimental study shows that on average, DSA-IS achieves the best time and space results of all of the existing external memory algorithms based on the induced sorting principle.