/// which is mostly copied from Glaurung 1.x, and not very pretty.
ScaleFactor KRPKRScalingFunction::apply(const Position &pos) {
+
assert(pos.non_pawn_material(strongerSide) == RookValueMidgame);
assert(pos.piece_count(strongerSide, PAWN) == 1);
assert(pos.non_pawn_material(weakerSide) == RookValueMidgame);
Square brsq = pos.piece_list(weakerSide, ROOK, 0);
// Orient the board in such a way that the stronger side is white, and the
- // pawn is on the left half of the board:
- if(strongerSide == BLACK) {
- wksq = flip_square(wksq);
- wrsq = flip_square(wrsq);
- wpsq = flip_square(wpsq);
- bksq = flip_square(bksq);
- brsq = flip_square(brsq);
+ // pawn is on the left half of the board.
+ if (strongerSide == BLACK)
+ {
+ wksq = flip_square(wksq);
+ wrsq = flip_square(wrsq);
+ wpsq = flip_square(wpsq);
+ bksq = flip_square(bksq);
+ brsq = flip_square(brsq);
}
- if(square_file(wpsq) > FILE_D) {
- wksq = flop_square(wksq);
- wrsq = flop_square(wrsq);
- wpsq = flop_square(wpsq);
- bksq = flop_square(bksq);
- brsq = flop_square(brsq);
+ if (square_file(wpsq) > FILE_D)
+ {
+ wksq = flop_square(wksq);
+ wrsq = flop_square(wrsq);
+ wpsq = flop_square(wpsq);
+ bksq = flop_square(bksq);
+ brsq = flop_square(brsq);
}
File f = square_file(wpsq);
int tempo = (pos.side_to_move() == strongerSide);
// If the pawn is not too far advanced and the defending king defends the
- // queening square, use the third-rank defence:
- if(r <= RANK_5 && square_distance(bksq, queeningSq) <= 1 && wksq <= SQ_H5 &&
- (square_rank(brsq) == RANK_6 || (r <= RANK_3 &&
- square_rank(wrsq) != RANK_6)))
- return ScaleFactor(0);
+ // queening square, use the third-rank defence.
+ if ( r <= RANK_5
+ && square_distance(bksq, queeningSq) <= 1
+ && wksq <= SQ_H5
+ && (square_rank(brsq) == RANK_6 || (r <= RANK_3 && square_rank(wrsq) != RANK_6)))
+ return ScaleFactor(0);
// The defending side saves a draw by checking from behind in case the pawn
// has advanced to the 6th rank with the king behind.
- if(r == RANK_6 && square_distance(bksq, queeningSq) <= 1 &&
- square_rank(wksq) + tempo <= RANK_6 &&
- (square_rank(brsq) == RANK_1 ||
- (!tempo && abs(square_file(brsq) - f) >= 3)))
- return ScaleFactor(0);
+ if ( r == RANK_6
+ && square_distance(bksq, queeningSq) <= 1
+ && square_rank(wksq) + tempo <= RANK_6
+ && (square_rank(brsq) == RANK_1 || (!tempo && abs(square_file(brsq) - f) >= 3)))
+ return ScaleFactor(0);
- if(r >= RANK_6 && bksq == queeningSq && square_rank(brsq) == RANK_1 &&
- (!tempo || square_distance(wksq, wpsq) >= 2))
- return ScaleFactor(0);
+ if ( r >= RANK_6
+ && bksq == queeningSq
+ && square_rank(brsq) == RANK_1
+ && (!tempo || square_distance(wksq, wpsq) >= 2))
+ return ScaleFactor(0);
// White pawn on a7 and rook on a8 is a draw if black's king is on g7 or h7
// and the black rook is behind the pawn.
- if(wpsq == SQ_A7 && wrsq == SQ_A8 && (bksq == SQ_H7 || bksq == SQ_G7) &&
- square_file(brsq) == FILE_A &&
- (square_rank(brsq) <= RANK_3 || square_file(wksq) >= FILE_D ||
- square_rank(wksq) <= RANK_5))
- return ScaleFactor(0);
+ if ( wpsq == SQ_A7
+ && wrsq == SQ_A8
+ && (bksq == SQ_H7 || bksq == SQ_G7)
+ && square_file(brsq) == FILE_A
+ && (square_rank(brsq) <= RANK_3 || square_file(wksq) >= FILE_D || square_rank(wksq) <= RANK_5))
+ return ScaleFactor(0);
// If the defending king blocks the pawn and the attacking king is too far
// away, it's a draw.
- if(r <= RANK_5 && bksq == wpsq + DELTA_N &&
- square_distance(wksq, wpsq) - tempo >= 2 &&
- square_distance(wksq, brsq) - tempo >= 2)
- return ScaleFactor(0);
+ if ( r <= RANK_5
+ && bksq == wpsq + DELTA_N
+ && square_distance(wksq, wpsq) - tempo >= 2
+ && square_distance(wksq, brsq) - tempo >= 2)
+ return ScaleFactor(0);
// Pawn on the 7th rank supported by the rook from behind usually wins if the
// attacking king is closer to the queening square than the defending king,
- // and the defending king cannot gain tempi by threatening the attacking
- // rook.
- if(r == RANK_7 && f != FILE_A && square_file(wrsq) == f
- && wrsq != queeningSq
- && (square_distance(wksq, queeningSq) <
- square_distance(bksq, queeningSq) - 2 + tempo)
- && (square_distance(wksq, queeningSq) <
- square_distance(bksq, wrsq) + tempo))
- return ScaleFactor(SCALE_FACTOR_MAX
- - 2 * square_distance(wksq, queeningSq));
-
- // Similar to the above, but with the pawn further back:
- if(f != FILE_A && square_file(wrsq) == f && wrsq < wpsq
- && (square_distance(wksq, queeningSq) <
- square_distance(bksq, queeningSq) - 2 + tempo)
- && (square_distance(wksq, wpsq + DELTA_N) <
- square_distance(bksq, wpsq + DELTA_N) - 2 + tempo)
- && (square_distance(bksq, wrsq) + tempo >= 3
- || (square_distance(wksq, queeningSq) <
- square_distance(bksq, wrsq) + tempo
- && (square_distance(wksq, wpsq + DELTA_N) <
- square_distance(bksq, wrsq) + tempo))))
- return
- ScaleFactor(SCALE_FACTOR_MAX
- - (8 * square_distance(wpsq, queeningSq) +
- 2 * square_distance(wksq, queeningSq)));
+ // and the defending king cannot gain tempi by threatening the attacking rook.
+ if ( r == RANK_7
+ && f != FILE_A
+ && square_file(wrsq) == f
+ && wrsq != queeningSq
+ && (square_distance(wksq, queeningSq) < square_distance(bksq, queeningSq) - 2 + tempo)
+ && (square_distance(wksq, queeningSq) < square_distance(bksq, wrsq) + tempo))
+ return ScaleFactor(SCALE_FACTOR_MAX - 2 * square_distance(wksq, queeningSq));
+
+ // Similar to the above, but with the pawn further back
+ if ( f != FILE_A
+ && square_file(wrsq) == f
+ && wrsq < wpsq
+ && (square_distance(wksq, queeningSq) < square_distance(bksq, queeningSq) - 2 + tempo)
+ && (square_distance(wksq, wpsq + DELTA_N) < square_distance(bksq, wpsq + DELTA_N) - 2 + tempo)
+ && ( square_distance(bksq, wrsq) + tempo >= 3
+ || ( square_distance(wksq, queeningSq) < square_distance(bksq, wrsq) + tempo
+ && (square_distance(wksq, wpsq + DELTA_N) < square_distance(bksq, wrsq) + tempo))))
+ return ScaleFactor( SCALE_FACTOR_MAX
+ - (8 * square_distance(wpsq, queeningSq)
+ + 2 * square_distance(wksq, queeningSq)));
// If the pawn is not far advanced, and the defending king is somewhere in
- // the pawn's path, it's probably a draw:
- if(r <= RANK_4 && bksq > wpsq) {
- if(square_file(bksq) == square_file(wpsq))
- return ScaleFactor(10);
- if(abs(square_file(bksq) - square_file(wpsq)) == 1
- && square_distance(wksq, bksq) > 2)
- return ScaleFactor(24 - 2 * square_distance(wksq, bksq));
+ // the pawn's path, it's probably a draw.
+ if (r <= RANK_4 && bksq > wpsq)
+ {
+ if (square_file(bksq) == square_file(wpsq))
+ return ScaleFactor(10);
+ if ( abs(square_file(bksq) - square_file(wpsq)) == 1
+ && square_distance(wksq, bksq) > 2)
+ return ScaleFactor(24 - 2 * square_distance(wksq, bksq));
}
-
return SCALE_FACTOR_NONE;
}
-/// KRPPKRPScalingFunction scales KRPP vs KRP endgames. There is only a
-/// single pattern: If the stronger side has no pawns and the defending king
+/// KRPPKRPScalingFunction scales KRPP vs KRP endgames. There is only a
+/// single pattern: If the stronger side has no pawns and the defending king
/// is actively placed, the position is drawish.
ScaleFactor KRPPKRPScalingFunction::apply(const Position &pos) {
+
assert(pos.non_pawn_material(strongerSide) == RookValueMidgame);
assert(pos.piece_count(strongerSide, PAWN) == 2);
assert(pos.non_pawn_material(weakerSide) == RookValueMidgame);
Square bksq = pos.king_square(weakerSide);
// Does the stronger side have a passed pawn?
- if(pos.pawn_is_passed(strongerSide, wpsq1) ||
- pos.pawn_is_passed(strongerSide, wpsq2))
- return SCALE_FACTOR_NONE;
+ if ( pos.pawn_is_passed(strongerSide, wpsq1)
+ || pos.pawn_is_passed(strongerSide, wpsq2))
+ return SCALE_FACTOR_NONE;
Rank r = Max(relative_rank(strongerSide, wpsq1), relative_rank(strongerSide, wpsq2));
- if(file_distance(bksq, wpsq1) <= 1 && file_distance(bksq, wpsq2) <= 1
- && relative_rank(strongerSide, bksq) > r) {
- switch(r) {
-
- case RANK_2: return ScaleFactor(10);
- case RANK_3: return ScaleFactor(10);
- case RANK_4: return ScaleFactor(15);
- case RANK_5: return ScaleFactor(20);
- case RANK_6: return ScaleFactor(40);
- default: assert(false);
-
- }
+ if ( file_distance(bksq, wpsq1) <= 1
+ && file_distance(bksq, wpsq2) <= 1
+ && relative_rank(strongerSide, bksq) > r)
+ {
+ switch (r) {
+ case RANK_2: return ScaleFactor(10);
+ case RANK_3: return ScaleFactor(10);
+ case RANK_4: return ScaleFactor(15);
+ case RANK_5: return ScaleFactor(20);
+ case RANK_6: return ScaleFactor(40);
+ default: assert(false);
+ }
}
return SCALE_FACTOR_NONE;
}
/// KPsKScalingFunction scales endgames with king and two or more pawns
-/// against king. There is just a single rule here: If all pawns are on
+/// against king. There is just a single rule here: If all pawns are on
/// the same rook file and are blocked by the defending king, it's a draw.
ScaleFactor KPsKScalingFunction::apply(const Position &pos) {
+
assert(pos.non_pawn_material(strongerSide) == Value(0));
assert(pos.piece_count(strongerSide, PAWN) >= 2);
assert(pos.non_pawn_material(weakerSide) == Value(0));
Bitboard pawns = pos.pawns(strongerSide);
// Are all pawns on the 'a' file?
- if((pawns & ~FileABB) == EmptyBoardBB) {
- // Does the defending king block the pawns?
- Square ksq = pos.king_square(weakerSide);
- if(square_distance(ksq, relative_square(strongerSide, SQ_A8)) <= 1)
- return ScaleFactor(0);
- else if(square_file(ksq) == FILE_A &&
- (in_front_bb(strongerSide, ksq) & pawns) == EmptyBoardBB)
- return ScaleFactor(0);
- else
- return SCALE_FACTOR_NONE;
+ if ((pawns & ~FileABB) == EmptyBoardBB)
+ {
+ // Does the defending king block the pawns?
+ Square ksq = pos.king_square(weakerSide);
+ if (square_distance(ksq, relative_square(strongerSide, SQ_A8)) <= 1)
+ return ScaleFactor(0);
+ else if( square_file(ksq) == FILE_A
+ && (in_front_bb(strongerSide, ksq) & pawns) == EmptyBoardBB)
+ return ScaleFactor(0);
+ else
+ return SCALE_FACTOR_NONE;
}
// Are all pawns on the 'h' file?
- else if((pawns & ~FileHBB) == EmptyBoardBB) {
+ else if ((pawns & ~FileHBB) == EmptyBoardBB)
+ {
// Does the defending king block the pawns?
Square ksq = pos.king_square(weakerSide);
- if(square_distance(ksq, relative_square(strongerSide, SQ_H8)) <= 1)
- return ScaleFactor(0);
- else if(square_file(ksq) == FILE_H &&
- (in_front_bb(strongerSide, ksq) & pawns) == EmptyBoardBB)
- return ScaleFactor(0);
+ if (square_distance(ksq, relative_square(strongerSide, SQ_H8)) <= 1)
+ return ScaleFactor(0);
+ else if ( square_file(ksq) == FILE_H
+ && (in_front_bb(strongerSide, ksq) & pawns) == EmptyBoardBB)
+ return ScaleFactor(0);
else
- return SCALE_FACTOR_NONE;
+ return SCALE_FACTOR_NONE;
}
else
- return SCALE_FACTOR_NONE;
+ return SCALE_FACTOR_NONE;
}
-/// KBPKBScalingFunction scales KBP vs KB endgames. There are two rules:
+/// KBPKBScalingFunction scales KBP vs KB endgames. There are two rules:
/// 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. If the two bishops have opposite color, it's almost always
+/// it's a draw. If the two bishops have opposite color, it's almost always
/// a draw.
ScaleFactor KBPKBScalingFunction::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);
Square weakerBishopSq = pos.piece_list(weakerSide, BISHOP, 0);
Square weakerKingSq = pos.king_square(weakerSide);
- // Case 1: Defending king blocks the pawn, and cannot be driven away.
- 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);
-
- // Case 2: Opposite colored bishops.
- if(square_color(strongerBishopSq) != square_color(weakerBishopSq)) {
-
- // We assume that the position is drawn in the following three situations:
- //
- // a. The pawn is on rank 5 or further back.
- // b. The defending king is somewhere in the pawn's path.
- // c. The defending bishop attacks some square along the pawn's path,
- // and is at least three squares away from the pawn.
- //
- // These rules are probably not perfect, but in practice they work
- // reasonably well.
-
- if(relative_rank(strongerSide, pawnSq) <= RANK_5)
+ // Case 1: Defending king blocks the pawn, and cannot be driven away
+ 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);
- else {
- Bitboard ray =
- ray_bb(pawnSq, (strongerSide == WHITE)? SIGNED_DIR_N : SIGNED_DIR_S);
- if(ray & pos.kings(weakerSide))
- return ScaleFactor(0);
- if((pos.piece_attacks<BISHOP>(weakerBishopSq) & ray)
- && square_distance(weakerBishopSq, pawnSq) >= 3)
- return ScaleFactor(0);
- }
+
+ // Case 2: Opposite colored bishops
+ if (square_color(strongerBishopSq) != square_color(weakerBishopSq))
+ {
+ // We assume that the position is drawn in the following three situations:
+ //
+ // a. The pawn is on rank 5 or further back.
+ // b. The defending king is somewhere in the pawn's path.
+ // c. The defending bishop attacks some square along the pawn's path,
+ // and is at least three squares away from the pawn.
+ //
+ // These rules are probably not perfect, but in practice they work
+ // reasonably well.
+
+ if (relative_rank(strongerSide, pawnSq) <= RANK_5)
+ return ScaleFactor(0);
+ else
+ {
+ Bitboard ray = ray_bb(pawnSq, (strongerSide == WHITE)? SIGNED_DIR_N : SIGNED_DIR_S);
+ if (ray & pos.kings(weakerSide))
+ return ScaleFactor(0);
+ 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);
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);
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);
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);
}
// 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));
}
-
}
projects / stockfish / blobdiff