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Fix the handling of opposite bishops in KXK endgame evaluation 

The case of three or more bishops against a long king must look at all of the
bishops and not just the first two in the piece lists. This patch makes sure
that the position is treated as a win when there are bishops on opposite
colors. This functional change is very small because bench remains the same.

LLR: 2.95 (-2.94,2.94) [-4.00,0.00]
Total: 24249 W: 4349 L: 4275 D: 15625
http://tests.stockfishchess.org/tests/view/598186530ebc5916ff64a218

Bench: 5608839
pull/1188/merge
tthsqe12 2017-08-12 10:50:38 +02:00 committed by Marco Costalba
parent 2783203428
commit 5837228aa0
1 changed files with 2 additions and 2 deletions
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4
src/endgame.cpp
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@ -135,8 +135,8 @@ Value Endgame<KXK>::operator()(const Position& pos) const {
if ( pos.count<QUEEN>(strongSide)
|| pos.count<ROOK>(strongSide)
||(pos.count<BISHOP>(strongSide) && pos.count<KNIGHT>(strongSide))
||(pos.count<BISHOP>(strongSide) > 1 && opposite_colors(pos.squares<BISHOP>(strongSide)[0],
pos.squares<BISHOP>(strongSide)[1])))
|| ( (pos.pieces(strongSide, BISHOP) & ~DarkSquares)
&& (pos.pieces(strongSide, BISHOP) & DarkSquares)))
result = std::min(result + VALUE_KNOWN_WIN, VALUE_MATE_IN_MAX_PLY - 1);
return strongSide == pos.side_to_move() ? result : -result;