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Article #115Re: Minimal Perfect Hashing Functions
From: Gordon V. Cormack
Date: Wed, 28 Nov 1984 03:26
Date: Wed, 28 Nov 1984 03:26
33 lines
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1855 bytes
You may (or may not) be interested in a paper by myself titled
"Practical perfect hashing" to appear the the next issue of
"The Computer Journal".
I am not claiming that this method is the best for a compiler, as
it requires 3 divisions per access. Indeed, it is not clear to me
why there exists this great desire for a perfect hash function in
this case. One can construct an ordinary hash table that performs
extremely well. I also see little need for a minimal function,
as the number of keywords is quite small.
If anyone can't wait for the above article to appear, send me a
message and I will send you a pre-print.
ABSTRACT
A practical method is presented that permits
retrieval from a table in constant time. The
method is suitable for large tables and consumes,
in practice, O(n) space for n table elements. In
addition, the table and the hashing function can
be constructed in O(n) expected time. Variations
of the method that offer different compromises
between storage usage and update time are present-
ed.
Gordon V. Cormack
Department of Computer Science
University of Waterloo
Waterloo, Ontario N2L 3G1
gvcormack@watdaisy.uucp
gvcormack%watdaisy@waterloo.csnet
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Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.1 6/24/83; site watdaisy.UUCP Path: arc1-ca.pugleaf.net!utzoo!watmath!watdaisy!gvcormack From: gvcormack@watdaisy.UUCP (Gordon V. Cormack) Newsgroups: net.lang.pascal Subject: Re: Minimal Perfect Hashing Functions Message-ID: <6772@watdaisy.UUCP> Date: Tue, 27-Nov-84 22:26:14 EST Article-I.D.: watdaisy.6772 Posted: Tue Nov 27 22:26:14 1984 Date-Received: Wed, 28-Nov-84 04:28:31 EST References: <684@loral.UUCP> Organization: U of Waterloo, Ontario Lines: 33