Understanding the Moments of Tabulation Hashing via Chaoses

Publikation: Bidrag til bog/antologi/rapportKonferencebidrag i proceedingsForskningfagfællebedømt

Dokumenter

  • Fulltext

    Forlagets udgivne version, 764 KB, PDF-dokument

Simple tabulation hashing dates back to Zobrist in 1970 and is defined as follows: Each key is viewed as c characters from some alphabet Σ, we have c fully random hash functions h0,..., hc−1: Σ → {0,..., 2l − 1}, and a key x = (x0,..., xc−1) is hashed to (Equation presented) where ⊕ is the bitwise XOR operation. The previous results on tabulation hashing by Pǎtraşcu and Thorup [J.ACM'11] and by Aamand et al. [STOC'20] focused on proving Chernoff-style tail bounds on hash-based sums, e.g., the number keys hashing to a given value, for simple tabulation hashing, but their bounds do not cover the entire tail. Thus their results cannot bound moments. The paper Dahlgaard et al. [FOCS'15] provides a bound on the moments of certain hash-based sums, but their bound only holds for constant moments, and we need logarithmic moments. Chaoses are random variables of the form (Equation presented) where Xi are independent random variables. Chaoses are a well-studied concept from probability theory, and tight analysis has been proven in several instances, e.g., when the independent random variables are standard Gaussian variables and when the independent random variables have logarithmically convex tails. We notice that hash-based sums of simple tabulation hashing can be seen as a sum of chaoses that are not independent. This motivates us to use techniques from the theory of chaoses to analyze hash-based sums of simple tabulation hashing. In this paper, we obtain bounds for all the moments of hash-based sums for simple tabulation hashing which are tight up to constants depending only on c. In contrast with the previous attempts, our approach will mostly be analytical and does not employ intricate combinatorial arguments. The improved analysis of simple tabulation hashing allows us to obtain bounds for the moments of hash-based sums for the mixed tabulation hashing introduced by Dahlgaard et al. [FOCS'15]. With simple tabulation hashing, there are certain inputs for which the concentration is much worse than with fully random hashing. However, with mixed tabulation, we get logarithmic moment bounds that are only a constant factor worse than those with fully random hashing for any possible input. This is a strong addition to other powerful probabilistic properties of mixed tabulation hashing proved by Dahlgaard et al.

OriginalsprogEngelsk
Titel49th EATCS International Conference on Automata, Languages, and Programming, ICALP 2022
RedaktørerMikolaj Bojanczyk, Emanuela Merelli, David P. Woodruff
ForlagSchloss Dagstuhl- Leibniz-Zentrum fur Informatik GmbH, Dagstuhl Publishing
Publikationsdatojul. 2022
Sider1-19
Artikelnummer74
ISBN (Elektronisk)9783959772358
DOI
StatusUdgivet - jul. 2022
Begivenhed49th EATCS International Conference on Automata, Languages, and Programming, ICALP 2022 - Paris, Frankrig
Varighed: 4 jul. 20228 jul. 2022

Konference

Konference49th EATCS International Conference on Automata, Languages, and Programming, ICALP 2022
LandFrankrig
ByParis
Periode04/07/202208/07/2022
SponsorCNRS, Inria, Nomadic Lab, Université Paris Cité
NavnLeibniz International Proceedings in Informatics, LIPIcs
Vol/bind229
ISSN1868-8969

Bibliografisk note

Funding Information:
Funding Research supported by Investigator Grant 16582, Basic Algorithms Research Copenhagen (BARC), from the VILLUM Foundation.

Publisher Copyright:
© Jakob Bæk Tejs Houen and Mikkel Thorup; licensed under Creative Commons License CC-BY 4.0

Antal downloads er baseret på statistik fra Google Scholar og www.ku.dk


Ingen data tilgængelig

ID: 314296202