Author: Robert Hyatt
Date: 10:59:12 12/05/01
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On December 05, 2001 at 11:53:10, Ratko V Tomic wrote: >>The problem is that you have 56 bits of information. 48 possible pawn >>positions + 8 possible en passant target files. > >En passant needs at most 3 bits. On average it would need much >less than even the 3 bits since after the position of pawns is >specified, the en passant bits (0-3 bits) may be added >conditionally as an index into the array of en passant >candidates. The 48 bits specifying the pawn position thus >automatically specify how many en passant bits follow. If you do it that way then you have to "assemble" things to get the pawn hash signature. I simply assumed a bitmap approach where of the 64 bits, 48 would be 0/1 depending on whether that square has a pawn or not, and the remaining 8 bits would be set if there is a possible enpassant capture on that file...
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