Author: David Rasmussen
Date: 04:11:41 12/03/01
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On December 02, 2001 at 23:58:43, Robert Hyatt wrote: >On December 02, 2001 at 22:38:30, David Rasmussen wrote: > >>Many people use 32-bit pawn hashkeys. But I've found that 32 bits is not enough >>to avoid collisions. 64-bit seems to be enough, and maybe less could do the job. >>Why do people use 32-bit keys, when it screws up evaluation this way? >> >>/David > > >32 is ok for pawns. To see why, figure out how many _different_ positions >there are with only pawns on the board. The number is not as large as you >might think, which makes collisions unlikely so long as you _only_ hash pawn >positions. I get the first collision after about 5 seconds of search, and the the rate increases as the search progresses. I believe I have good random numbers, I have checked hamming distance etc. I don't use separate values for pawn hashing (as you did at some point, I think), I just use the first n bits of the normal hashkeys for pawns, where n=64 now that I've found n=32 not to work. /David
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