Author: Ralf Elvsén
Date: 01:50:09 11/14/01
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On November 14, 2001 at 04:48:05, Ralf Elvsén wrote: >On November 13, 2001 at 19:19:46, David Hanley wrote: > >>It's my understanding that the hash codes used in a chess program are hamming >>codes, and they are generated such that >> >>bit_count( code[x]^ code[y] ) > threshold >> >>for all combinations of codes, obviously self excluded. >> >>Is this correct? >> >>I plan on using 48 bit hash codes, and my threshold for bit mismatches is >>hash_length/6, or in the case of 48 bit keys, 8 bit differences. Is this >>sufficient? >> > >It has been argued here (and I think it is correct) that the Hamming >distance shouldn't be too big either, i.e. 47 is as bad as 1. > >I did this for 64 bits, and I tried to push all pairwise Hamming >distances as close to 32 as possible, e.g. > >minimize( maximum(abs(32 - Hammingdistance(r_i, r_j)) ) ) > >where r_i are the random numbers and i != j . I got a value of 24 or >so (don't remember exactly). It seems to work fairly well. > >Ralf What I tried to say was that the hamming distances ended between 24 and 40... Ralf
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