Author: Gerd Isenberg
Date: 10:30:41 09/08/02
Go up one level in this thread
To evaluate this position as "won" for white a few pattern matcher are necessary
(bitboards required):
1. Endgame with opposite colored bishops ("weaker" side may have an additional
knight, "stronger" side has passers).
2. "Stronger" King with only one friendly bishop and (passed) pawns stands patt
("Stronger" side is noted as black now).
3. Black has no capture.
4. WB controlles adjacent king square exclusively, there is no other defender
rather than the BK (b7).
5. All black pawn move targtes to WB-colored squares are controlled by WB on one
diagonal but not defended at all (no former duo).
6. All other pawn moves to BB-colored squares (here c5 only) are blocked (but
not by king) or match condition 5 afterwards (the target-targets are controlled
by WB but one the same diagonal and not defended att all).
7. No pawn move leaves an escape square for the patt standing BK.
8. WK is not (exclusively) involved to trap opposites king and free to walk
around.
9. All adjacent BK-squares are either occupied by black pawns or controlled by
white pieces, so the King is stalemated forever.
If all these conditions match, it's time to give a bonus at least results in a
draw score:
max(-materialbalance(white), 0)
... and to disable nullmove for black to move, if not already done in these kind
of positions.
Now we are looking for a target square for the WK, so that the WB may mate
protected by his king. With the help of pattern 3 we find the b8,c8 target set
here.
If the square set is reachable by WK detouring adjacent to most advanced black
passer which stop is controlled by WB, it's a won position.
As long as the shortest king way to the target square(s) interrups the bishop
ray to black pawn targtes, we force the king toward most advanced black passer
(h2). Otherwise we gave a larger bonus the shorter the distance to c8/b8 is.
OK, not yet implemented. Worth to try?
Gerd
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