A cuckoo hashing variant with improved memory utilization and insertion time

Ely Porat, Bar Shalem

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

3 Scopus citations

Abstract

Cuckoo hashing [4] is a multiple choice hashing scheme in which each item can be placed in multiple locations, and collisions are resolved by moving items to their alternative locations. In the classical implementation of two-way cuckoo hashing, the memory is partitioned into contiguous disjoint fixed-size buckets. Each item is hashed to two buckets, and may be stored in any of the positions within those buckets. Ref. [2] analyzed a variation in which the buckets are contiguous and overlap. However, many systems retrieve data from secondary storage in same-size blocks called pages. Fetching a page is a relatively expensive process; but once a page is fetched, its contents can be accessed orders of magnitude faster. We utilize this property of memory retrieval, presenting a variant of cuckoo hashing incorporating the following constraint: each bucket must be fully contained in a single page, but buckets are not necessarily contiguous. Empirical results show that this modification increases memory utilization and decreases the number of iterations required to insert an item. If each item is hashed to two buckets of capacity two, the page size is 8, and each bucket is fully contained in a single page, the memory utilization equals 89.71% in the classical contiguous disjoint bucket variant, 93.78% in the contiguous overlapping bucket variant, and increases to 97.46% in our new non-contiguous bucket variant. When the memory utilization is 92% and we use breadth first search to look for a vacant position, the number of iterations required to insert a new item is dramatically reduced from 545 in the contiguous overlapping buckets variant to 52 in our new non-contiguous bucket variant. In addition to the empirical results, we present a theoretical lower bound on the memory utilization of our variation as a function of the page size.

Original languageEnglish
Title of host publicationProceedings - DCC 2012
Subtitle of host publication2012 Data Compression Conference
Pages347-356
Number of pages10
DOIs
StatePublished - 2012
Event2012 Data Compression Conference, DCC 2012 - Snowbird, UT, United States
Duration: 10 Apr 201212 Apr 2012

Publication series

NameData Compression Conference Proceedings
ISSN (Print)1068-0314

Conference

Conference2012 Data Compression Conference, DCC 2012
Country/TerritoryUnited States
CitySnowbird, UT
Period10/04/1212/04/12

Keywords

  • CUCKOO HASHING
  • Pages

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