Order-preserving minimal perfect hash functions and information retrieval
نویسندگان
چکیده
منابع مشابه
Generating Minimal Perfect Hash Functions
The randomized, deterministic and parallel algorithms for generating minimal perfect hash functions (MPHF) are proposed. Given a set of keys, W, which are character strings over some alphabet, the algorithms using a three-step approach (mapping, ordering, searching) nd the MPHF of the form h(w) = (h0(w) + g(h1(w)) + g(h2(w)))mod m, w 2 W, where h0, h1, h2 are auxiliary pseudorandom functions, m...
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A new way of constructing (minimal) perfect hash functions is described. The technique considerably reduces the overhead associated with resolving buckets in two-level hashing schemes. Evaluating a hash function requires just one multiplication and a few additions apart from primitive bit operations. The number of accesses to memory is two, one of which is to a fixed location. This improves the...
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An ordered minimal perfect hash table is one in which no collisions occur among a prede ned set of keys, no space is unused and the data are placed in the table in order. A new method for creating ordered minimal perfect hash functions is presented. It creates hash functions with representation space requirements closer to the theoretical lower bound than previous methods. The method presented ...
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A perfect hash function (PHF) h : U → [0, m − 1] for a key set S is a function that maps the keys of S to unique values. The minimum amount of space to represent a PHF for a given set S is known to be approximately 1.44n/m bits, where n = |S|. In this paper we present new algorithms for construction and evaluation of PHFs of a given set (for m = n and m = 1.23n), with the following properties: ...
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Recent advances in random linear systems on finite fields have paved the way for the construction of constant-time data structures representing static functions and minimal perfect hash functions using less space with respect to existing techniques. The main obstruction for any practical application of these results is the cubic-time Gaussian elimination required to solve these linear systems: ...
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ژورنال
عنوان ژورنال: ACM Transactions on Information Systems
سال: 1991
ISSN: 1046-8188,1558-2868
DOI: 10.1145/125187.125200