Author: leonid
Date: 18:16:19 11/25/99
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On November 25, 1999 at 17:58:27, Heiner Marxen wrote: >>For me the fact of recognition os the check is almost as >>time consuming as legality of all the pieces beside the king > >If you know the last move, which leads to the position in question, >you need not search much to find the checking piece(s). With the >exception of e.p. and castling moves, there are just two chances: >(d) the last moved piece may give a direct check from its target square >(i) the last moved piece may have discovered a check on its source square > >(i) is possible only, if your king´s square is related to the last pieces >from square: on same row, column or diagonal. That can be detected fast. >For (d) similar geometric considerations are possible. > >Heiner Very good consideration and very well explained! I must look into it. The only inconvience here I see in two facts: 1) Once mistake about the position of the king could lead to the accumulation and mistakes and collapse of entire game. When on each new position all the data about the fire against the king is recollected, such domino effect is excuded. 2) All the data that recognize the legality of the moves, beyond the moves of the king, will be not available. This data is recollected in the same procedure that recognize if the king is under the fire. Leonid.
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