Author: Robert Hyatt
Date: 11:18:13 01/14/98
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On January 14, 1998 at 14:04:53, John Bartkiw wrote: > > Just a question for anyone. I've noticed most people are using a >table of random numbers to use instead of the actual bitboards. Can >someone give me the reasoning for this? Is it do to the sparseness of >the bitboards? > yes and no. If you use the bitboards only, you couldn't tell the difference between a king on a2 and a pawn on a3 and a king on a3 and a pawn on a2, which would be a killer. Random numbers will tend to have about 1/2 of the bits set to zero, the other half set to 1. So moving a single piece affects *lots* of bits, rather than only 2... to make the hash distribution more uniform. >John. > >> >>The key in seq A would be something like: >>origKey ^ randTable[white][king][c3] ^ >> randTable[black][king][c6] ^ >> randTable[white][king][b2] >> >>And for B: >>origKey ^ randTable[white][king][c1] ^ >> randTable[black][king][c6] ^ >> randTable[white][king][b2] >>
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