Uniform hashing is optimal
- 1 July 1985
- journal article
- Published by Association for Computing Machinery (ACM) in Journal of the ACM
- Vol. 32 (3) , 687-693
- https://doi.org/10.1145/3828.3836
Abstract
It was conjectured by J. Ullman that uniform hashing is optimal in its expected retrieval cost among all open-address hashing schemes [4]. In this paper, we show that, for any open-address hashing scheme, the expected cost of retrieving a record from a large table that is α-fraction full is at least (1/α) log (1/(1 - α)) + o (1). This proves Ullman's conjecture to be true in the asymptotic sense.Keywords
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