Near‐perfect hashing of large word sets

Abstract

This article presents a procedure for constructing a near‐perfect hashing function. The procedure, which is a modification of Cichelli's algorithm, builds the near‐perfect hashing function sufficiently fast to allow larger word sets to be used than were previously possible. The improved procedure is the result of examining the original algorithm for the causes of its sluggish performance and then modifying them. In doing so an attempt was made to preserve the basic simplicity of th original algorithm. The improved performance comes at the expense of more storage. The six modifications used to improve performance are explained in detail and experimental results are given for word sets of varying sizes.

Practical minimal perfect hash functions for large databases

“…Some approaches require input keys to already be integers in some restricted range, while others are really two-level searches in which extra storage in each bucket supports the second level of search. An example is the work of Brain and Tharp, which extends Cichelli's approach, but still cannot handle very large key sets [1].…”