A Practical Alphabet-Partitioning Rank/Select Data Structure

This paper proposes a practical implementation of an alphabet-partitioning compressed data structure, which represents a string within compressed space and supports the fundamental operations \(\mathsf {rank}\) and \(\mathsf {select}\) efficiently. We show experimental results that indicate that our implementation outperforms the current realizations of the alphabet-partitioning approach (which is one of the most efficient approaches in practice). In particular, the time for operation \(\mathsf {select}\) can be reduced by about 80%, using only 11% more space than current alphabet-partitioning schemes. We also show the impact of our data structure on several applications, like the intersection of inverted lists (where improvements of up to 60% are achieved, using only 2% of extra space), and the distributed-computation processing of \(\mathsf {rank}\) and \(\mathsf {select}\) operations. As far as we know, this is the first study about the support of \(\mathsf {rank}\)/\(\mathsf {select}\) operations on a distributed-computing environment.