Robin hood hashing

Abstract

This paper deals with hash tables in which conflicts are resolved by open addressing. The initial contribution is a very simple insertion procedure which (in comparison to the standard approach) has the effect of dramatically reducing the variance of the number of probes required for a search. This leads to a new search procedure which requires only a constant number of probes, on average, even for full tables. Finally, an extension to these methods yields a new, simple way of performing deletions and subsequent insertions. Experimental results strongly indicate little degeneration in search time. In particular deletions and successful searches appear to require constant time (≪ 2.57 probes) and insertions and unsuccessful searches, O(logn).