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Final endgame.cpp space inflate
No functional change. Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba
parent
c32904f0a0
commit
82bf08e4f2
1 changed files with 188 additions and 173 deletions
361
src/endgame.cpp
361
src/endgame.cpp
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@ -559,6 +559,7 @@ ScaleFactor KQKRPScalingFunction::apply(const Position& pos) {
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/// which is mostly copied from Glaurung 1.x, and not very pretty.
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ScaleFactor KRPKRScalingFunction::apply(const Position &pos) {
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assert(pos.non_pawn_material(strongerSide) == RookValueMidgame);
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assert(pos.piece_count(strongerSide, PAWN) == 1);
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assert(pos.non_pawn_material(weakerSide) == RookValueMidgame);
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@ -571,20 +572,22 @@ ScaleFactor KRPKRScalingFunction::apply(const Position &pos) {
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Square brsq = pos.piece_list(weakerSide, ROOK, 0);
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// Orient the board in such a way that the stronger side is white, and the
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// pawn is on the left half of the board:
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if(strongerSide == BLACK) {
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wksq = flip_square(wksq);
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wrsq = flip_square(wrsq);
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wpsq = flip_square(wpsq);
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bksq = flip_square(bksq);
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brsq = flip_square(brsq);
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// pawn is on the left half of the board.
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if (strongerSide == BLACK)
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{
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wksq = flip_square(wksq);
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wrsq = flip_square(wrsq);
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wpsq = flip_square(wpsq);
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bksq = flip_square(bksq);
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brsq = flip_square(brsq);
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}
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if(square_file(wpsq) > FILE_D) {
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wksq = flop_square(wksq);
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wrsq = flop_square(wrsq);
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wpsq = flop_square(wpsq);
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bksq = flop_square(bksq);
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brsq = flop_square(brsq);
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if (square_file(wpsq) > FILE_D)
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{
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wksq = flop_square(wksq);
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wrsq = flop_square(wrsq);
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wpsq = flop_square(wpsq);
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bksq = flop_square(bksq);
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brsq = flop_square(brsq);
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}
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File f = square_file(wpsq);
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@ -593,87 +596,88 @@ ScaleFactor KRPKRScalingFunction::apply(const Position &pos) {
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int tempo = (pos.side_to_move() == strongerSide);
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// If the pawn is not too far advanced and the defending king defends the
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// queening square, use the third-rank defence:
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if(r <= RANK_5 && square_distance(bksq, queeningSq) <= 1 && wksq <= SQ_H5 &&
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(square_rank(brsq) == RANK_6 || (r <= RANK_3 &&
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square_rank(wrsq) != RANK_6)))
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return ScaleFactor(0);
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// queening square, use the third-rank defence.
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if ( r <= RANK_5
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&& square_distance(bksq, queeningSq) <= 1
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&& wksq <= SQ_H5
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&& (square_rank(brsq) == RANK_6 || (r <= RANK_3 && square_rank(wrsq) != RANK_6)))
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return ScaleFactor(0);
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// The defending side saves a draw by checking from behind in case the pawn
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// has advanced to the 6th rank with the king behind.
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if(r == RANK_6 && square_distance(bksq, queeningSq) <= 1 &&
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square_rank(wksq) + tempo <= RANK_6 &&
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(square_rank(brsq) == RANK_1 ||
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(!tempo && abs(square_file(brsq) - f) >= 3)))
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return ScaleFactor(0);
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if ( r == RANK_6
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&& square_distance(bksq, queeningSq) <= 1
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&& square_rank(wksq) + tempo <= RANK_6
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&& (square_rank(brsq) == RANK_1 || (!tempo && abs(square_file(brsq) - f) >= 3)))
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return ScaleFactor(0);
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if(r >= RANK_6 && bksq == queeningSq && square_rank(brsq) == RANK_1 &&
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(!tempo || square_distance(wksq, wpsq) >= 2))
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return ScaleFactor(0);
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if ( r >= RANK_6
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&& bksq == queeningSq
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&& square_rank(brsq) == RANK_1
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&& (!tempo || square_distance(wksq, wpsq) >= 2))
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return ScaleFactor(0);
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// White pawn on a7 and rook on a8 is a draw if black's king is on g7 or h7
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// and the black rook is behind the pawn.
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if(wpsq == SQ_A7 && wrsq == SQ_A8 && (bksq == SQ_H7 || bksq == SQ_G7) &&
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square_file(brsq) == FILE_A &&
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(square_rank(brsq) <= RANK_3 || square_file(wksq) >= FILE_D ||
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square_rank(wksq) <= RANK_5))
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return ScaleFactor(0);
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if ( wpsq == SQ_A7
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&& wrsq == SQ_A8
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&& (bksq == SQ_H7 || bksq == SQ_G7)
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&& square_file(brsq) == FILE_A
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&& (square_rank(brsq) <= RANK_3 || square_file(wksq) >= FILE_D || square_rank(wksq) <= RANK_5))
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return ScaleFactor(0);
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// If the defending king blocks the pawn and the attacking king is too far
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// away, it's a draw.
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if(r <= RANK_5 && bksq == wpsq + DELTA_N &&
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square_distance(wksq, wpsq) - tempo >= 2 &&
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square_distance(wksq, brsq) - tempo >= 2)
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return ScaleFactor(0);
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if ( r <= RANK_5
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&& bksq == wpsq + DELTA_N
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&& square_distance(wksq, wpsq) - tempo >= 2
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&& square_distance(wksq, brsq) - tempo >= 2)
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return ScaleFactor(0);
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// Pawn on the 7th rank supported by the rook from behind usually wins if the
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// attacking king is closer to the queening square than the defending king,
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// and the defending king cannot gain tempi by threatening the attacking
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// rook.
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if(r == RANK_7 && f != FILE_A && square_file(wrsq) == f
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&& wrsq != queeningSq
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&& (square_distance(wksq, queeningSq) <
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square_distance(bksq, queeningSq) - 2 + tempo)
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&& (square_distance(wksq, queeningSq) <
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square_distance(bksq, wrsq) + tempo))
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return ScaleFactor(SCALE_FACTOR_MAX
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- 2 * square_distance(wksq, queeningSq));
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// and the defending king cannot gain tempi by threatening the attacking rook.
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if ( r == RANK_7
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&& f != FILE_A
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&& square_file(wrsq) == f
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&& wrsq != queeningSq
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&& (square_distance(wksq, queeningSq) < square_distance(bksq, queeningSq) - 2 + tempo)
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&& (square_distance(wksq, queeningSq) < square_distance(bksq, wrsq) + tempo))
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return ScaleFactor(SCALE_FACTOR_MAX - 2 * square_distance(wksq, queeningSq));
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// Similar to the above, but with the pawn further back:
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if(f != FILE_A && square_file(wrsq) == f && wrsq < wpsq
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&& (square_distance(wksq, queeningSq) <
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square_distance(bksq, queeningSq) - 2 + tempo)
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&& (square_distance(wksq, wpsq + DELTA_N) <
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square_distance(bksq, wpsq + DELTA_N) - 2 + tempo)
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&& (square_distance(bksq, wrsq) + tempo >= 3
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|| (square_distance(wksq, queeningSq) <
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square_distance(bksq, wrsq) + tempo
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&& (square_distance(wksq, wpsq + DELTA_N) <
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square_distance(bksq, wrsq) + tempo))))
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return
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ScaleFactor(SCALE_FACTOR_MAX
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- (8 * square_distance(wpsq, queeningSq) +
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2 * square_distance(wksq, queeningSq)));
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// Similar to the above, but with the pawn further back
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if ( f != FILE_A
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&& square_file(wrsq) == f
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&& wrsq < wpsq
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&& (square_distance(wksq, queeningSq) < square_distance(bksq, queeningSq) - 2 + tempo)
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&& (square_distance(wksq, wpsq + DELTA_N) < square_distance(bksq, wpsq + DELTA_N) - 2 + tempo)
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&& ( square_distance(bksq, wrsq) + tempo >= 3
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|| ( square_distance(wksq, queeningSq) < square_distance(bksq, wrsq) + tempo
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&& (square_distance(wksq, wpsq + DELTA_N) < square_distance(bksq, wrsq) + tempo))))
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return ScaleFactor( SCALE_FACTOR_MAX
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- (8 * square_distance(wpsq, queeningSq)
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+ 2 * square_distance(wksq, queeningSq)));
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// If the pawn is not far advanced, and the defending king is somewhere in
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// the pawn's path, it's probably a draw:
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if(r <= RANK_4 && bksq > wpsq) {
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if(square_file(bksq) == square_file(wpsq))
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return ScaleFactor(10);
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if(abs(square_file(bksq) - square_file(wpsq)) == 1
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&& square_distance(wksq, bksq) > 2)
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return ScaleFactor(24 - 2 * square_distance(wksq, bksq));
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// the pawn's path, it's probably a draw.
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if (r <= RANK_4 && bksq > wpsq)
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{
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if (square_file(bksq) == square_file(wpsq))
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return ScaleFactor(10);
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if ( abs(square_file(bksq) - square_file(wpsq)) == 1
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&& square_distance(wksq, bksq) > 2)
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return ScaleFactor(24 - 2 * square_distance(wksq, bksq));
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}
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return SCALE_FACTOR_NONE;
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}
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/// KRPPKRPScalingFunction scales KRPP vs KRP endgames. There is only a
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/// single pattern: If the stronger side has no pawns and the defending king
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/// KRPPKRPScalingFunction scales KRPP vs KRP endgames. There is only a
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/// single pattern: If the stronger side has no pawns and the defending king
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/// is actively placed, the position is drawish.
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ScaleFactor KRPPKRPScalingFunction::apply(const Position &pos) {
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assert(pos.non_pawn_material(strongerSide) == RookValueMidgame);
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assert(pos.piece_count(strongerSide, PAWN) == 2);
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assert(pos.non_pawn_material(weakerSide) == RookValueMidgame);
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@ -684,34 +688,35 @@ ScaleFactor KRPPKRPScalingFunction::apply(const Position &pos) {
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Square bksq = pos.king_square(weakerSide);
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// Does the stronger side have a passed pawn?
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if(pos.pawn_is_passed(strongerSide, wpsq1) ||
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pos.pawn_is_passed(strongerSide, wpsq2))
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return SCALE_FACTOR_NONE;
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if ( pos.pawn_is_passed(strongerSide, wpsq1)
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|| pos.pawn_is_passed(strongerSide, wpsq2))
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return SCALE_FACTOR_NONE;
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Rank r = Max(relative_rank(strongerSide, wpsq1), relative_rank(strongerSide, wpsq2));
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if(file_distance(bksq, wpsq1) <= 1 && file_distance(bksq, wpsq2) <= 1
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&& relative_rank(strongerSide, bksq) > r) {
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switch(r) {
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case RANK_2: return ScaleFactor(10);
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case RANK_3: return ScaleFactor(10);
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case RANK_4: return ScaleFactor(15);
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case RANK_5: return ScaleFactor(20);
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case RANK_6: return ScaleFactor(40);
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default: assert(false);
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}
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if ( file_distance(bksq, wpsq1) <= 1
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&& file_distance(bksq, wpsq2) <= 1
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&& relative_rank(strongerSide, bksq) > r)
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{
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switch (r) {
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case RANK_2: return ScaleFactor(10);
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case RANK_3: return ScaleFactor(10);
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case RANK_4: return ScaleFactor(15);
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case RANK_5: return ScaleFactor(20);
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case RANK_6: return ScaleFactor(40);
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default: assert(false);
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}
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}
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return SCALE_FACTOR_NONE;
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}
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/// KPsKScalingFunction scales endgames with king and two or more pawns
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/// against king. There is just a single rule here: If all pawns are on
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/// against king. There is just a single rule here: If all pawns are on
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/// the same rook file and are blocked by the defending king, it's a draw.
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ScaleFactor KPsKScalingFunction::apply(const Position &pos) {
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assert(pos.non_pawn_material(strongerSide) == Value(0));
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assert(pos.piece_count(strongerSide, PAWN) >= 2);
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assert(pos.non_pawn_material(weakerSide) == Value(0));
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@ -720,41 +725,44 @@ ScaleFactor KPsKScalingFunction::apply(const Position &pos) {
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Bitboard pawns = pos.pawns(strongerSide);
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// Are all pawns on the 'a' file?
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if((pawns & ~FileABB) == EmptyBoardBB) {
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// Does the defending king block the pawns?
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Square ksq = pos.king_square(weakerSide);
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if(square_distance(ksq, relative_square(strongerSide, SQ_A8)) <= 1)
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return ScaleFactor(0);
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else if(square_file(ksq) == FILE_A &&
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(in_front_bb(strongerSide, ksq) & pawns) == EmptyBoardBB)
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return ScaleFactor(0);
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else
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return SCALE_FACTOR_NONE;
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if ((pawns & ~FileABB) == EmptyBoardBB)
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{
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// Does the defending king block the pawns?
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Square ksq = pos.king_square(weakerSide);
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if (square_distance(ksq, relative_square(strongerSide, SQ_A8)) <= 1)
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return ScaleFactor(0);
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else if( square_file(ksq) == FILE_A
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&& (in_front_bb(strongerSide, ksq) & pawns) == EmptyBoardBB)
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return ScaleFactor(0);
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else
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return SCALE_FACTOR_NONE;
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}
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// Are all pawns on the 'h' file?
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else if((pawns & ~FileHBB) == EmptyBoardBB) {
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else if ((pawns & ~FileHBB) == EmptyBoardBB)
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{
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// Does the defending king block the pawns?
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Square ksq = pos.king_square(weakerSide);
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if(square_distance(ksq, relative_square(strongerSide, SQ_H8)) <= 1)
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return ScaleFactor(0);
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else if(square_file(ksq) == FILE_H &&
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(in_front_bb(strongerSide, ksq) & pawns) == EmptyBoardBB)
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return ScaleFactor(0);
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if (square_distance(ksq, relative_square(strongerSide, SQ_H8)) <= 1)
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return ScaleFactor(0);
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else if ( square_file(ksq) == FILE_H
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&& (in_front_bb(strongerSide, ksq) & pawns) == EmptyBoardBB)
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return ScaleFactor(0);
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else
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return SCALE_FACTOR_NONE;
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return SCALE_FACTOR_NONE;
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}
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else
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return SCALE_FACTOR_NONE;
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return SCALE_FACTOR_NONE;
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}
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/// KBPKBScalingFunction scales KBP vs KB endgames. There are two rules:
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/// KBPKBScalingFunction scales KBP vs KB endgames. There are two rules:
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/// If the defending king is somewhere along the path of the pawn, and the
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/// square of the king is not of the same color as the stronger side's bishop,
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/// it's a draw. If the two bishops have opposite color, it's almost always
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/// it's a draw. If the two bishops have opposite color, it's almost always
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/// a draw.
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ScaleFactor KBPKBScalingFunction::apply(const Position &pos) {
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assert(pos.non_pawn_material(strongerSide) == BishopValueMidgame);
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assert(pos.piece_count(strongerSide, BISHOP) == 1);
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assert(pos.piece_count(strongerSide, PAWN) == 1);
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@ -767,48 +775,49 @@ ScaleFactor KBPKBScalingFunction::apply(const Position &pos) {
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Square weakerBishopSq = pos.piece_list(weakerSide, BISHOP, 0);
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Square weakerKingSq = pos.king_square(weakerSide);
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// Case 1: Defending king blocks the pawn, and cannot be driven away.
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if(square_file(weakerKingSq) == square_file(pawnSq)
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&& relative_rank(strongerSide, pawnSq) < relative_rank(strongerSide, weakerKingSq)
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&& (square_color(weakerKingSq) != square_color(strongerBishopSq)
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|| relative_rank(strongerSide, weakerKingSq) <= RANK_6))
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return ScaleFactor(0);
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// Case 2: Opposite colored bishops.
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if(square_color(strongerBishopSq) != square_color(weakerBishopSq)) {
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// We assume that the position is drawn in the following three situations:
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//
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// a. The pawn is on rank 5 or further back.
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// b. The defending king is somewhere in the pawn's path.
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// c. The defending bishop attacks some square along the pawn's path,
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// and is at least three squares away from the pawn.
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//
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// These rules are probably not perfect, but in practice they work
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// reasonably well.
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if(relative_rank(strongerSide, pawnSq) <= RANK_5)
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// Case 1: Defending king blocks the pawn, and cannot be driven away
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if ( square_file(weakerKingSq) == square_file(pawnSq)
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&& relative_rank(strongerSide, pawnSq) < relative_rank(strongerSide, weakerKingSq)
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&& ( square_color(weakerKingSq) != square_color(strongerBishopSq)
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|| relative_rank(strongerSide, weakerKingSq) <= RANK_6))
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return ScaleFactor(0);
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else {
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Bitboard ray =
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ray_bb(pawnSq, (strongerSide == WHITE)? SIGNED_DIR_N : SIGNED_DIR_S);
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if(ray & pos.kings(weakerSide))
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return ScaleFactor(0);
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if((pos.piece_attacks<BISHOP>(weakerBishopSq) & ray)
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&& square_distance(weakerBishopSq, pawnSq) >= 3)
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return ScaleFactor(0);
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}
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// Case 2: Opposite colored bishops
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if (square_color(strongerBishopSq) != square_color(weakerBishopSq))
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{
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// We assume that the position is drawn in the following three situations:
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//
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// a. The pawn is on rank 5 or further back.
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// b. The defending king is somewhere in the pawn's path.
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// c. The defending bishop attacks some square along the pawn's path,
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// and is at least three squares away from the pawn.
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//
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// These rules are probably not perfect, but in practice they work
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// reasonably well.
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if (relative_rank(strongerSide, pawnSq) <= RANK_5)
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return ScaleFactor(0);
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else
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{
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Bitboard ray = ray_bb(pawnSq, (strongerSide == WHITE)? SIGNED_DIR_N : SIGNED_DIR_S);
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if (ray & pos.kings(weakerSide))
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return ScaleFactor(0);
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if( (pos.piece_attacks<BISHOP>(weakerBishopSq) & ray)
|
||||
&& square_distance(weakerBishopSq, pawnSq) >= 3)
|
||||
return ScaleFactor(0);
|
||||
}
|
||||
}
|
||||
return SCALE_FACTOR_NONE;
|
||||
}
|
||||
|
||||
|
||||
/// KBPKNScalingFunction scales KBP vs KN endgames. There is a single rule:
|
||||
/// KBPKNScalingFunction scales KBP vs KN endgames. There is a single rule:
|
||||
/// If the defending king is somewhere along the path of the pawn, and the
|
||||
/// square of the king is not of the same color as the stronger side's bishop,
|
||||
/// it's a draw.
|
||||
|
||||
ScaleFactor KBPKNScalingFunction::apply(const Position &pos) {
|
||||
|
||||
assert(pos.non_pawn_material(strongerSide) == BishopValueMidgame);
|
||||
assert(pos.piece_count(strongerSide, BISHOP) == 1);
|
||||
assert(pos.piece_count(strongerSide, PAWN) == 1);
|
||||
|
|
@ -820,21 +829,22 @@ ScaleFactor KBPKNScalingFunction::apply(const Position &pos) {
|
|||
Square strongerBishopSq = pos.piece_list(strongerSide, BISHOP, 0);
|
||||
Square weakerKingSq = pos.king_square(weakerSide);
|
||||
|
||||
if(square_file(weakerKingSq) == square_file(pawnSq)
|
||||
&& relative_rank(strongerSide, pawnSq) < relative_rank(strongerSide, weakerKingSq)
|
||||
&& (square_color(weakerKingSq) != square_color(strongerBishopSq)
|
||||
|| relative_rank(strongerSide, weakerKingSq) <= RANK_6))
|
||||
return ScaleFactor(0);
|
||||
if ( square_file(weakerKingSq) == square_file(pawnSq)
|
||||
&& relative_rank(strongerSide, pawnSq) < relative_rank(strongerSide, weakerKingSq)
|
||||
&& ( square_color(weakerKingSq) != square_color(strongerBishopSq)
|
||||
|| relative_rank(strongerSide, weakerKingSq) <= RANK_6))
|
||||
return ScaleFactor(0);
|
||||
|
||||
return SCALE_FACTOR_NONE;
|
||||
}
|
||||
|
||||
|
||||
/// KNPKScalingFunction scales KNP vs K endgames. There is a single rule:
|
||||
/// KNPKScalingFunction scales KNP vs K endgames. There is a single rule:
|
||||
/// If the pawn is a rook pawn on the 7th rank and the defending king prevents
|
||||
/// the pawn from advancing, the position is drawn.
|
||||
|
||||
ScaleFactor KNPKScalingFunction::apply(const Position &pos) {
|
||||
|
||||
assert(pos.non_pawn_material(strongerSide) == KnightValueMidgame);
|
||||
assert(pos.piece_count(strongerSide, KNIGHT) == 1);
|
||||
assert(pos.piece_count(strongerSide, PAWN) == 1);
|
||||
|
|
@ -844,26 +854,27 @@ ScaleFactor KNPKScalingFunction::apply(const Position &pos) {
|
|||
Square pawnSq = pos.piece_list(strongerSide, PAWN, 0);
|
||||
Square weakerKingSq = pos.king_square(weakerSide);
|
||||
|
||||
if(pawnSq == relative_square(strongerSide, SQ_A7) &&
|
||||
square_distance(weakerKingSq, relative_square(strongerSide, SQ_A8)) <= 1)
|
||||
return ScaleFactor(0);
|
||||
if ( pawnSq == relative_square(strongerSide, SQ_A7)
|
||||
&& square_distance(weakerKingSq, relative_square(strongerSide, SQ_A8)) <= 1)
|
||||
return ScaleFactor(0);
|
||||
|
||||
if(pawnSq == relative_square(strongerSide, SQ_H7) &&
|
||||
square_distance(weakerKingSq, relative_square(strongerSide, SQ_H8)) <= 1)
|
||||
return ScaleFactor(0);
|
||||
if ( pawnSq == relative_square(strongerSide, SQ_H7)
|
||||
&& square_distance(weakerKingSq, relative_square(strongerSide, SQ_H8)) <= 1)
|
||||
return ScaleFactor(0);
|
||||
|
||||
return SCALE_FACTOR_NONE;
|
||||
}
|
||||
|
||||
|
||||
/// KPKPScalingFunction scales KP vs KP endgames. This is done by removing
|
||||
/// the weakest side's pawn and probing the KP vs K bitbase: If the weakest
|
||||
/// KPKPScalingFunction scales KP vs KP endgames. This is done by removing
|
||||
/// the weakest side's pawn and probing the KP vs K bitbase: If the weakest
|
||||
/// side has a draw without the pawn, she probably has at least a draw with
|
||||
/// the pawn as well. The exception is when the stronger side's pawn is far
|
||||
/// the pawn as well. The exception is when the stronger side's pawn is far
|
||||
/// advanced and not on a rook file; in this case it is often possible to win
|
||||
/// (e.g. 8/4k3/3p4/3P4/6K1/8/8/8 w - - 0 1).
|
||||
|
||||
ScaleFactor KPKPScalingFunction::apply(const Position &pos) {
|
||||
|
||||
assert(pos.non_pawn_material(strongerSide) == Value(0));
|
||||
assert(pos.non_pawn_material(weakerSide) == Value(0));
|
||||
assert(pos.piece_count(WHITE, PAWN) == 1);
|
||||
|
|
@ -872,36 +883,40 @@ ScaleFactor KPKPScalingFunction::apply(const Position &pos) {
|
|||
Square wksq, bksq, wpsq;
|
||||
Color stm;
|
||||
|
||||
if(strongerSide == WHITE) {
|
||||
wksq = pos.king_square(WHITE);
|
||||
bksq = pos.king_square(BLACK);
|
||||
wpsq = pos.piece_list(WHITE, PAWN, 0);
|
||||
stm = pos.side_to_move();
|
||||
if (strongerSide == WHITE)
|
||||
{
|
||||
wksq = pos.king_square(WHITE);
|
||||
bksq = pos.king_square(BLACK);
|
||||
wpsq = pos.piece_list(WHITE, PAWN, 0);
|
||||
stm = pos.side_to_move();
|
||||
}
|
||||
else {
|
||||
wksq = flip_square(pos.king_square(BLACK));
|
||||
bksq = flip_square(pos.king_square(WHITE));
|
||||
wpsq = flip_square(pos.piece_list(BLACK, PAWN, 0));
|
||||
stm = opposite_color(pos.side_to_move());
|
||||
else
|
||||
{
|
||||
wksq = flip_square(pos.king_square(BLACK));
|
||||
bksq = flip_square(pos.king_square(WHITE));
|
||||
wpsq = flip_square(pos.piece_list(BLACK, PAWN, 0));
|
||||
stm = opposite_color(pos.side_to_move());
|
||||
}
|
||||
|
||||
if(square_file(wpsq) >= FILE_E) {
|
||||
wksq = flop_square(wksq);
|
||||
bksq = flop_square(bksq);
|
||||
wpsq = flop_square(wpsq);
|
||||
if (square_file(wpsq) >= FILE_E)
|
||||
{
|
||||
wksq = flop_square(wksq);
|
||||
bksq = flop_square(bksq);
|
||||
wpsq = flop_square(wpsq);
|
||||
}
|
||||
|
||||
// If the pawn has advanced to the fifth rank or further, and is not a
|
||||
// rook pawn, it's too dangerous to assume that it's at least a draw.
|
||||
if(square_rank(wpsq) >= RANK_5 && square_file(wpsq) != FILE_A)
|
||||
return SCALE_FACTOR_NONE;
|
||||
if ( square_rank(wpsq) >= RANK_5
|
||||
&& square_file(wpsq) != FILE_A)
|
||||
return SCALE_FACTOR_NONE;
|
||||
|
||||
// Probe the KPK bitbase with the weakest side's pawn removed. If it's a
|
||||
// Probe the KPK bitbase with the weakest side's pawn removed. If it's a
|
||||
// draw, it's probably at least a draw even with the pawn.
|
||||
if(probe_kpk(wksq, wpsq, bksq, stm))
|
||||
return SCALE_FACTOR_NONE;
|
||||
if (probe_kpk(wksq, wpsq, bksq, stm))
|
||||
return SCALE_FACTOR_NONE;
|
||||
else
|
||||
return ScaleFactor(0);
|
||||
return ScaleFactor(0);
|
||||
}
|
||||
|
||||
|
||||
|
|
@ -919,11 +934,11 @@ namespace {
|
|||
// Probe the KP vs K bitbase:
|
||||
|
||||
int probe_kpk(Square wksq, Square wpsq, Square bksq, Color stm) {
|
||||
|
||||
int wp = int(square_file(wpsq)) + (int(square_rank(wpsq)) - 1) * 4;
|
||||
int index = int(stm) + 2*int(bksq) + 128*int(wksq) + 8192*wp;
|
||||
|
||||
assert(index >= 0 && index < 24576*8);
|
||||
return KPKBitbase[index/8] & (1 << (index&7));
|
||||
}
|
||||
|
||||
}
|
||||
|
|
|
|||
Loading…
Add table
Reference in a new issue