Static dictionaries on AC0 RAMs: query time (√log n/log log n) is necessary and sufficient

Arne Andersson, Peter Bro Miltersen, Søren Riis, Mikkel Thorup

    Publikation: Bidrag til bog/antologi/rapport/proceedingKonferencebidrag i proceedingsForskningpeer review

    Abstract

    In this paper we consider solutions to the static dictionary problem on AC0 RAMs, i.e. random access machines where the only restriction on the finite instruction set is that all computational instructions are in AC0. Our main result is a tight upper and lower bound of θ(√log n/log log n) on the time for answering membership queries in a set of size n when reasonable space is used for the data structure storing the set; the upper bound can be obtained using O(n) space, and the lower bound holds even if we allow space 2polylog n. Several variations of this result are also obtained. Among others, we show a tradeoff between time and circuit depth under the unit-cost assumption: any RAM instruction set which permits a linear space, constant query time solution to the static dictionary problem must have an instruction of depth Ω(log w/log log to), where w is the word size of the machine (and log the size of the universe). This matches the depth of multiplication and integer division, used in the perfect hashing scheme by M.L. Fredman, J. Komlos and E. Szemeredi (1984)
    OriginalsprogEngelsk
    Titel37th Annual Symposium on Foundations of Computer Science, 1996. Proceedings.
    Antal sider10
    ForlagIEEE Computer Society Press
    Publikationsdato1996
    Sider441-450
    DOI
    StatusUdgivet - 1996
    BegivenhedAnnual Symposium on Foundations of Computer Science - Burlington, VT, USA
    Varighed: 14 okt. 199616 okt. 1996
    Konferencens nummer: 37

    Konference

    KonferenceAnnual Symposium on Foundations of Computer Science
    Nummer37
    Land/OmrådeUSA
    ByBurlington, VT
    Periode14/10/199616/10/1996

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