Author: Robert Hyatt
Date: 07:02:39 01/16/04
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On January 15, 2004 at 14:49:21, Bernward Klocke wrote: >I recently read Ed Schroeder's comments on move ordering in rebel. What I find >puzzeling is the way it detects hanging pieces. >Ed presents the following data structure for square evaluation: >+------+------+------+------+------+------+------+------+ >| BIT0 | BIT1 | BIT2 | BIT3 | BIT4 | BIT5 | BIT6 | BIT7 | >+------+------+------+------+------+------+------+------+ >| Number of | PAWN |KNIGHT| ROOK | QUEEN| KING | >| ATTACKERS | |BISHOP| | | | >+------+------+------+------+------+------+------+------+ > >After all white pieces are done square F3 from WB looks as follows: >+------+------+------+------+------+------+------+------+ B0-B2 : 2 attackers >| BIT0 | BIT1 | BIT2 | BIT3 | BIT4 | BIT5 | BIT6 | BIT7 | >+------+------+------+------+------+------+------+------+ B3 : white pawn >| Number of | PAWN |KNIGHT| ROOK | QUEEN| KING | >| ATTACKERS | |BISHOP| | | | B4 : white >knight/bishop >+------+------+------+------+------+------+------+------+ >| 0 | 1 | 0 | 1 | 1 | 0 | 0 | 0 | >+------+------+------+------+------+------+------+------+ >So evaluation is done for each square for black and for white. His example show >the square f3 for white attacked by a pawn from f3 and a knight from g1. >This example is clear but I think gets ambiguous when three pieces attack a >square and two of them are of the same type eg. two rooks and a knight. How can >one see that it's not two knights and one rook. >And the other thing is only going through the movelist isn't the whole story. >What if doubled rooks are the attackers? Only the first one will appear in the >movelist. >Does anybody know how this is solved. What did I miss? >Otherwise the lookup from a precalculated table of STATUS values seems elegant. > >Bernward I would worry about overflow there. IE e4 could be attacked by pawns on d3 and f3, a bishop at d5 with a queen behind it (4 so far), plus two rooks and two knights. That's 8. It just overflowed to zero. Not to mention the promotion problems where there is a third knight or bishop or second queen...
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