Author: Andrew Dados
Date: 09:19:38 02/07/01
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On February 07, 2001 at 10:59:31, Pat King wrote: >I have seen it written here that with 64 bit Zobrist hashing, the perfect key >should change 32 bits. When I had what I thought to be hashing problems, I >captured some stats on my hash keys. I found that most of them changed 28-36 >bits (within 4) with a few outliers as far as 13 bits from "perfection". I also >checked that I was not generating duplicate keys. How good or bad is this? >Should I work on the average, or the outliers? Any comments appreciated :) > >Pat You need about 800 random 64 bit values with maximized hamming distance (different number of bits for each pair of 64 bit keys). According to my experiments you can do much better then 32 (Why the perfect key should change 32? It should change as much as possible...). I managed to generate 800 keys with hamming distance of 40 (so each key pair differ in exactly 40 bits); 41 seem to hit some limits around 760 keys. -Andrew-
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