Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!asuvax!stjhmc!f14.n15.z1.fidonet.org!Dave.Harris
From: Dave.Harris@f14.n15.z1.fidonet.org (Dave Harris)
Newsgroups: comp.lang.c
Subject: Re: hash function for mac needed
Message-ID: <14491.28619071@stjhmc.fidonet.org>
Date: 21 Jun 91 05:11:40 GMT
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Organization: FidoNet node 1:15/14 - Nibbles 'n Bits, Orem UT
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In a message of <Jun 18 20:29>, Chris Torek (1:114/15) writes: 

 >Indeed: as it turns out, while many people have spent much time looking
 >for `good' hashing functions, fewer seem to have noted that many
 >hashing systems spend more time computing hashes than searching.  I
 >find that this is usually the case, and that a fast hash function is
 >better than a slower-but-better-distribution function.  One good hash
 >function, useful in many applications, is this:

 >        hash = 0;
 >        for (each character)
 >                hash = (hash * 33) + (the character);
 >        hash_index = hash & ((some power of two) - 1);

Is the *33 use to keep short sequences has key more random or does it really 
help in the distribution of large string too?

  

 


 

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