Recursive n-gram hashing is pairwise independent, at best [r-libre/227]

Lemire, Daniel et Kaser, Owen (2010). Recursive n-gram hashing is pairwise independent, at best. Computer Speech & Language, 24 (4), 698-710. https://doi.org/10.1016/j.csl.2009.12.001

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Catégorie de document :	Articles de revues
Évaluation par un comité de lecture :	Oui
Étape de publication :	Publié
Résumé :	Many applications use sequences of n consecutive symbols (n-grams). Hashing these n-grams can be a performance bottleneck. For more speed, recursive hash families compute hash values by updating previous values. We prove that recursive hash families cannot be more than pairwise independent. While hashing by irreducible polynomials is pairwise independent, our implementations either run in time O(n) or use an exponential amount of memory. As a more scalable alternative, we make hashing by cyclic polynomials pairwise independent by ignoring n-1 bits. Experimentally, we show that hashing by cyclic polynomials is is twice as fast as hashing by irreducible polynomials. We also show that randomized Karp-Rabin hash families are not pairwise independent.
Adresse de la version officielle :	http://www.sciencedirect.com/science/article/pii/S...
Déposant:	Lemire, Daniel
Responsable :	Daniel Lemire
Dépôt :	22 juill. 2014 21:58
Dernière modification :	16 juill. 2015 00:46

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