Fast set intersection in memory

Set intersection is a fundamental operation in information retrieval and database systems. This paper introduces linear space data struc-tures to represent sets such that their intersection can be computed in a worst-case efficient way. In general, given k (preprocessed) sets, with totally n elements, we will show how to compute their intersection in expected time O(n/ w + kr), where r is the in-tersection size and w is the number of bits in a machine-word. In addition,we introduce a very simple version of this algorithm that has weaker asymptotic guarantees but performs even better in prac-tice; both algorithms outperform the state of the art techniques for both synthetic and real data sets and workloads. 1