The random walk $d$-ary cuckoo hashing algorithm was defined by Fotakis, Pagh, Sanders, and Spirakis to generalize and improve upon the standard cuckoo hashing algorithm of Pagh and Rodler. Random walk $d$-ary cuckoo hashing has low space overhead, guaranteed fast access, and fast in practice insertion time. In this paper, we give a theoretical insertion time bound for this algorithm. More precisely, for every $d\ge 3$ hashes, let $c_d^*$ be the sharp threshold for the load factor at which a valid assignment of $cm$ objects to a hash table of size $m$ likely exists. We show that for any $d\ge 4$ hashes and load factor $c<c_d^*$, the expectation of the random walk insertion time is $O(1)$, that is, a constant depending only on $d$ and $c$ but not $m$.
翻译:随机行走d-ary布谷鸟哈希算法由Fotakis、Pagh、Sanders和Spirakis提出,旨在推广并改进Pagh与Rodler的标准布谷鸟哈希算法。该算法具有低空间开销、保证快速访问以及实际中快速的插入时间。本文为该算法提供了理论上的插入时间界。具体而言,对每个$d\ge 3$哈希函数,设$c_d^*$为负载因子的严格阈值,使得大小为$m$的哈希表存在$cm$个对象的有效赋值。我们证明:对任意$d\ge 4$哈希函数及负载因子$c<c_d^*$,随机行走插入时间的期望为$O(1)$,即仅依赖于$d$和$c$而与$m$无关的常数。