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Subject: Re: pawn structure, pawn hash, square-of-pawn, pawn-races

Author: Robert Hyatt

Date: 07:59:16 08/20/04

Go up one level in this thread


On August 20, 2004 at 05:05:19, Tord Romstad wrote:

>On August 20, 2004 at 00:37:26, Eric Oldre wrote:
>
>>On August 19, 2004 at 18:46:32, Robert Hyatt wrote:
>>>
>>>
>>>Has to do with passed pawns and no pieces on the board.  If you form a square
>>>with one side going from the pawn to its promotion square, if the king is inside
>>>that square, the pawn can't run and promote.  If the king is outside that square
>>>then the pawn promotes and wins.  Simple idea with a few wrinkles to deal with.
>>
>>Thanks Robert,
>>that is actuall something I know i've read about at some point on this board.
>>and it's something that i hope i'll get to at some point.
>>
>>wouldn't you need to have 2 different bit boards? depending on who's turn it is
>>to move?
>
>You don't need even a single bitboard.  Just compare the distance of the
>passed pawn to the promotion square to the distance of the defending king
>to the promotion square.  Subtract 1 from the defending king's distance
>if it is the defender's turn to move.
>
>Tord
>

Bitboards don't need any subtraction, any correction for side to move, nor even
the exact king square.  It looks something like this:

if (white_pawn_race[square of white pawn] & BlackKing) pawn can't run.


>>
>>Eric



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