Author: Heiner Marxen
Date: 08:45:55 11/26/99
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On November 25, 1999 at 21:16:19, leonid wrote: >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. Ok, but that would be a bug, which has to be corrected. Therefore, I have a debug mode, which before and after each make or unmake move checks all redundant data for validity. Can be *very* helpful. Recommended. >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. Therefore my program generates strictly legal moves, only. The way I do it, it does not cost more than it gains. And the additional redundant data (attack data for all squares) does help a lot at other places. But that is different for every program, there is no single best way to do it. Heiner Marxen heiner@drb.insel.de http://www.drb.insel.de/~heiner/
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