/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
- Copyright (C) 2008 Marco Costalba
+ Copyright (C) 2008-2009 Marco Costalba
Stockfish is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
-
+
Stockfish is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
-
+
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <cassert>
#include "bitbase.h"
+#include "bitcount.h"
#include "endgame.h"
-////
-//// Constants and variables
-////
-
-/// Evaluation functions
-
-// Generic "mate lone king" eval:
-KXKEvaluationFunction EvaluateKXK = KXKEvaluationFunction(WHITE);
-KXKEvaluationFunction EvaluateKKX = KXKEvaluationFunction(BLACK);
-
-// KBN vs K:
-KBNKEvaluationFunction EvaluateKBNK = KBNKEvaluationFunction(WHITE);
-KBNKEvaluationFunction EvaluateKKBN = KBNKEvaluationFunction(BLACK);
-
-// KP vs K:
-KPKEvaluationFunction EvaluateKPK = KPKEvaluationFunction(WHITE);
-KPKEvaluationFunction EvaluateKKP = KPKEvaluationFunction(BLACK);
-
-// KR vs KP:
-KRKPEvaluationFunction EvaluateKRKP = KRKPEvaluationFunction(WHITE);
-KRKPEvaluationFunction EvaluateKPKR = KRKPEvaluationFunction(BLACK);
-
-// KR vs KB:
-KRKBEvaluationFunction EvaluateKRKB = KRKBEvaluationFunction(WHITE);
-KRKBEvaluationFunction EvaluateKBKR = KRKBEvaluationFunction(BLACK);
-
-// KR vs KN:
-KRKNEvaluationFunction EvaluateKRKN = KRKNEvaluationFunction(WHITE);
-KRKNEvaluationFunction EvaluateKNKR = KRKNEvaluationFunction(BLACK);
-
-// KQ vs KR:
-KQKREvaluationFunction EvaluateKQKR = KQKREvaluationFunction(WHITE);
-KQKREvaluationFunction EvaluateKRKQ = KQKREvaluationFunction(BLACK);
-
-// KBB vs KN:
-KBBKNEvaluationFunction EvaluateKBBKN = KBBKNEvaluationFunction(WHITE);
-KBBKNEvaluationFunction EvaluateKNKBB = KBBKNEvaluationFunction(BLACK);
-
-// K and two minors vs K and one or two minors:
-KmmKmEvaluationFunction EvaluateKmmKm = KmmKmEvaluationFunction(WHITE);
-
-
-/// Scaling functions
-
-// KBP vs K:
-KBPKScalingFunction ScaleKBPK = KBPKScalingFunction(WHITE);
-KBPKScalingFunction ScaleKKBP = KBPKScalingFunction(BLACK);
-
-// KQ vs KRP:
-KQKRPScalingFunction ScaleKQKRP = KQKRPScalingFunction(WHITE);
-KQKRPScalingFunction ScaleKRPKQ = KQKRPScalingFunction(BLACK);
-
-// KRP vs KR:
-KRPKRScalingFunction ScaleKRPKR = KRPKRScalingFunction(WHITE);
-KRPKRScalingFunction ScaleKRKRP = KRPKRScalingFunction(BLACK);
-
-// KRPP vs KRP:
-KRPPKRPScalingFunction ScaleKRPPKRP = KRPPKRPScalingFunction(WHITE);
-KRPPKRPScalingFunction ScaleKRPKRPP = KRPPKRPScalingFunction(BLACK);
-
-// King and pawns vs king:
-KPsKScalingFunction ScaleKPsK = KPsKScalingFunction(WHITE);
-KPsKScalingFunction ScaleKKPs = KPsKScalingFunction(BLACK);
-
-// KBP vs KB:
-KBPKBScalingFunction ScaleKBPKB = KBPKBScalingFunction(WHITE);
-KBPKBScalingFunction ScaleKBKBP = KBPKBScalingFunction(BLACK);
-
-// KBP vs KN:
-KBPKNScalingFunction ScaleKBPKN = KBPKNScalingFunction(WHITE);
-KBPKNScalingFunction ScaleKNKBP = KBPKNScalingFunction(BLACK);
-
-// KNP vs K:
-KNPKScalingFunction ScaleKNPK = KNPKScalingFunction(WHITE);
-KNPKScalingFunction ScaleKKNP = KNPKScalingFunction(BLACK);
-
-// KPKP
-KPKPScalingFunction ScaleKPKPw = KPKPScalingFunction(WHITE);
-KPKPScalingFunction ScaleKPKPb = KPKPScalingFunction(BLACK);
-
-
////
//// Local definitions
////
namespace {
// Table used to drive the defending king towards the edge of the board
- // in KX vs K and KQ vs KR endgames:
+ // in KX vs K and KQ vs KR endgames.
const uint8_t MateTable[64] = {
100, 90, 80, 70, 70, 80, 90, 100,
- 90, 70, 60, 50, 50, 60, 70, 90,
- 80, 60, 40, 30, 30, 40, 60, 80,
- 70, 50, 30, 20, 20, 30, 50, 70,
- 70, 50, 30, 20, 20, 30, 50, 70,
- 80, 60, 40, 30, 30, 40, 60, 80,
- 90, 70, 60, 50, 50, 60, 70, 90,
+ 90, 70, 60, 50, 50, 60, 70, 90,
+ 80, 60, 40, 30, 30, 40, 60, 80,
+ 70, 50, 30, 20, 20, 30, 50, 70,
+ 70, 50, 30, 20, 20, 30, 50, 70,
+ 80, 60, 40, 30, 30, 40, 60, 80,
+ 90, 70, 60, 50, 50, 60, 70, 90,
100, 90, 80, 70, 70, 80, 90, 100,
};
// Table used to drive the defending king towards a corner square of the
- // right color in KBN vs K endgames:
+ // right color in KBN vs K endgames.
const uint8_t KBNKMateTable[64] = {
200, 190, 180, 170, 160, 150, 140, 130,
190, 180, 170, 160, 150, 140, 130, 140,
};
// The attacking side is given a descending bonus based on distance between
- // the two kings in basic endgames:
- const int DistanceBonus[8] = {0, 0, 100, 80, 60, 40, 20, 10};
+ // the two kings in basic endgames.
+ const int DistanceBonus[8] = { 0, 0, 100, 80, 60, 40, 20, 10 };
- // Bitbase for KP vs K:
+ // Bitbase for KP vs K
uint8_t KPKBitbase[24576];
// Penalty for big distance between king and knight for the defending king
- // and knight in KR vs KN endgames:
+ // and knight in KR vs KN endgames.
const int KRKNKingKnightDistancePenalty[8] = { 0, 0, 4, 10, 20, 32, 48, 70 };
- // Various inline functions for accessing the above arrays:
-
+ // Various inline functions for accessing the above arrays
inline Value mate_table(Square s) {
return Value(MateTable[s]);
}
return Value(KRKNKingKnightDistancePenalty[d]);
}
- // Function for probing the KP vs K bitbase:
+ // Function for probing the KP vs K bitbase
int probe_kpk(Square wksq, Square wpsq, Square bksq, Color stm);
}
-
+
////
//// Functions
////
-/// Constructors
-
-EndgameEvaluationFunction::EndgameEvaluationFunction(Color c) {
- strongerSide = c;
- weakerSide = opposite_color(strongerSide);
-}
-
-KXKEvaluationFunction::KXKEvaluationFunction(Color c) : EndgameEvaluationFunction(c) { }
-KBNKEvaluationFunction::KBNKEvaluationFunction(Color c) : EndgameEvaluationFunction(c) { }
-KPKEvaluationFunction::KPKEvaluationFunction(Color c) : EndgameEvaluationFunction(c) { }
-KRKPEvaluationFunction::KRKPEvaluationFunction(Color c) : EndgameEvaluationFunction(c) { }
-KRKBEvaluationFunction::KRKBEvaluationFunction(Color c) : EndgameEvaluationFunction(c) { }
-KRKNEvaluationFunction::KRKNEvaluationFunction(Color c) : EndgameEvaluationFunction(c) { }
-KQKREvaluationFunction::KQKREvaluationFunction(Color c) : EndgameEvaluationFunction(c) { }
-KBBKNEvaluationFunction::KBBKNEvaluationFunction(Color c) : EndgameEvaluationFunction(c) { }
-KmmKmEvaluationFunction::KmmKmEvaluationFunction(Color c) : EndgameEvaluationFunction(c) { }
-
-
-ScalingFunction::ScalingFunction(Color c) {
- strongerSide = c;
- weakerSide = opposite_color(c);
-}
-
-KBPKScalingFunction::KBPKScalingFunction(Color c) : ScalingFunction(c) { }
-KQKRPScalingFunction::KQKRPScalingFunction(Color c) : ScalingFunction(c) { }
-KRPKRScalingFunction::KRPKRScalingFunction(Color c) : ScalingFunction(c) { }
-KRPPKRPScalingFunction::KRPPKRPScalingFunction(Color c) : ScalingFunction(c) { }
-KPsKScalingFunction::KPsKScalingFunction(Color c) : ScalingFunction(c) { }
-KBPKBScalingFunction::KBPKBScalingFunction(Color c) : ScalingFunction(c) { }
-KBPKNScalingFunction::KBPKNScalingFunction(Color c) : ScalingFunction(c) { }
-KNPKScalingFunction::KNPKScalingFunction(Color c) : ScalingFunction(c) { }
-KPKPScalingFunction::KPKPScalingFunction(Color c) : ScalingFunction(c) { }
-
-
-/// Mate with KX vs K. This function is used to evaluate positions with
-/// King and plenty of material vs a lone king. It simply gives the
+/// Mate with KX vs K. This function is used to evaluate positions with
+/// King and plenty of material vs a lone king. It simply gives the
/// attacking side a bonus for driving the defending king towards the edge
/// of the board, and for keeping the distance between the two kings small.
-
-Value KXKEvaluationFunction::apply(const Position &pos) {
+template<>
+Value EvaluationFunction<KXK>::apply(const Position& pos) {
assert(pos.non_pawn_material(weakerSide) == Value(0));
assert(pos.piece_count(weakerSide, PAWN) == Value(0));
Square winnerKSq = pos.king_square(strongerSide);
Square loserKSq = pos.king_square(weakerSide);
- Value result =
- pos.non_pawn_material(strongerSide) +
- pos.piece_count(strongerSide, PAWN) * PawnValueEndgame +
- mate_table(loserKSq) +
- distance_bonus(square_distance(winnerKSq, loserKSq));
+ Value result = pos.non_pawn_material(strongerSide)
+ + pos.piece_count(strongerSide, PAWN) * PawnValueEndgame
+ + mate_table(loserKSq)
+ + distance_bonus(square_distance(winnerKSq, loserKSq));
- if(pos.piece_count(strongerSide, QUEEN) > 0 || pos.piece_count(strongerSide, ROOK) > 0 ||
- pos.piece_count(strongerSide, BISHOP) > 1)
- // TODO: check for two equal-colored bishops!
- result += VALUE_KNOWN_WIN;
+ if ( pos.piece_count(strongerSide, QUEEN) > 0
+ || pos.piece_count(strongerSide, ROOK) > 0
+ || pos.piece_count(strongerSide, BISHOP) > 1)
+ // TODO: check for two equal-colored bishops!
+ result += VALUE_KNOWN_WIN;
- return (strongerSide == pos.side_to_move())? result : -result;
+ return (strongerSide == pos.side_to_move() ? result : -result);
}
-/// Mate with KBN vs K. This is similar to KX vs K, but we have to drive the
+/// Mate with KBN vs K. This is similar to KX vs K, but we have to drive the
/// defending king towards a corner square of the right color.
-
-Value KBNKEvaluationFunction::apply(const Position &pos) {
+template<>
+Value EvaluationFunction<KBNK>::apply(const Position& pos) {
assert(pos.non_pawn_material(weakerSide) == Value(0));
assert(pos.piece_count(weakerSide, PAWN) == Value(0));
- assert(pos.non_pawn_material(strongerSide) ==
- KnightValueMidgame + BishopValueMidgame);
+ assert(pos.non_pawn_material(strongerSide) == KnightValueMidgame + BishopValueMidgame);
assert(pos.piece_count(strongerSide, BISHOP) == 1);
assert(pos.piece_count(strongerSide, KNIGHT) == 1);
assert(pos.piece_count(strongerSide, PAWN) == 0);
Square loserKSq = pos.king_square(weakerSide);
Square bishopSquare = pos.piece_list(strongerSide, BISHOP, 0);
- if(square_color(bishopSquare) == BLACK) {
- winnerKSq = flop_square(winnerKSq);
- loserKSq = flop_square(loserKSq);
+ if (square_color(bishopSquare) == BLACK)
+ {
+ winnerKSq = flop_square(winnerKSq);
+ loserKSq = flop_square(loserKSq);
}
- Value result =
- VALUE_KNOWN_WIN + distance_bonus(square_distance(winnerKSq, loserKSq)) +
- kbnk_mate_table(loserKSq);
+ Value result = VALUE_KNOWN_WIN
+ + distance_bonus(square_distance(winnerKSq, loserKSq))
+ + kbnk_mate_table(loserKSq);
- return (strongerSide == pos.side_to_move())? result : -result;
+ return (strongerSide == pos.side_to_move() ? result : -result);
}
-/// KP vs K. This endgame is evaluated with the help of a bitbase.
-
-Value KPKEvaluationFunction::apply(const Position &pos) {
+/// KP vs K. This endgame is evaluated with the help of a bitbase.
+template<>
+Value EvaluationFunction<KPK>::apply(const Position& pos) {
assert(pos.non_pawn_material(strongerSide) == Value(0));
assert(pos.non_pawn_material(weakerSide) == Value(0));
assert(pos.piece_count(strongerSide, PAWN) == 1);
assert(pos.piece_count(weakerSide, PAWN) == 0);
-
+
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) {
+ if (square_file(wpsq) >= FILE_E)
+ {
wksq = flop_square(wksq);
bksq = flop_square(bksq);
wpsq = flop_square(wpsq);
}
- if(probe_kpk(wksq, wpsq, bksq, stm)) {
- Value result =
- VALUE_KNOWN_WIN + PawnValueEndgame + Value(square_rank(wpsq));
- return (strongerSide == pos.side_to_move())? result : -result;
- }
+ if (!probe_kpk(wksq, wpsq, bksq, stm))
+ return VALUE_DRAW;
- return VALUE_DRAW;
+ Value result = VALUE_KNOWN_WIN
+ + PawnValueEndgame
+ + Value(square_rank(wpsq));
+
+ return (strongerSide == pos.side_to_move() ? result : -result);
}
-/// KR vs KP. This is a somewhat tricky endgame to evaluate precisely without
-/// a bitbase. The function below returns drawish scores when the pawn is
+/// KR vs KP. This is a somewhat tricky endgame to evaluate precisely without
+/// a bitbase. The function below returns drawish scores when the pawn is
/// far advanced with support of the king, while the attacking king is far
/// away.
-
-Value KRKPEvaluationFunction::apply(const Position &pos) {
+template<>
+Value EvaluationFunction<KRKP>::apply(const Position& pos) {
assert(pos.non_pawn_material(strongerSide) == RookValueMidgame);
assert(pos.piece_count(strongerSide, PAWN) == 0);
bksq = pos.king_square(weakerSide);
bpsq = pos.piece_list(weakerSide, PAWN, 0);
- if(strongerSide == BLACK) {
- wksq = flip_square(wksq);
- wrsq = flip_square(wrsq);
- bksq = flip_square(bksq);
- bpsq = flip_square(bpsq);
+ if (strongerSide == BLACK)
+ {
+ wksq = flip_square(wksq);
+ wrsq = flip_square(wrsq);
+ bksq = flip_square(bksq);
+ bpsq = flip_square(bpsq);
}
Square queeningSq = make_square(square_file(bpsq), RANK_1);
Value result;
- // If the stronger side's king is in front of the pawn, it's a win:
- if(wksq < bpsq && square_file(wksq) == square_file(bpsq))
- result = RookValueEndgame - Value(square_distance(wksq, bpsq));
+ // If the stronger side's king is in front of the pawn, it's a win
+ if (wksq < bpsq && square_file(wksq) == square_file(bpsq))
+ result = RookValueEndgame - Value(square_distance(wksq, bpsq));
// If the weaker side's king is too far from the pawn and the rook,
- // it's a win:
- else if(square_distance(bksq, bpsq) - (tempo^1) >= 3 &&
- square_distance(bksq, wrsq) >= 3)
- result = RookValueEndgame - Value(square_distance(wksq, bpsq));
+ // it's a win
+ else if ( square_distance(bksq, bpsq) - (tempo^1) >= 3
+ && square_distance(bksq, wrsq) >= 3)
+ result = RookValueEndgame - Value(square_distance(wksq, bpsq));
// If the pawn is far advanced and supported by the defending king,
- // the position is drawish:
- else if(square_rank(bksq) <= RANK_3 && square_distance(bksq, bpsq) == 1 &&
- square_rank(wksq) >= RANK_4 &&
- square_distance(wksq, bpsq) - tempo > 2)
- result = Value(80 - square_distance(wksq, bpsq) * 8);
+ // the position is drawish
+ else if ( square_rank(bksq) <= RANK_3
+ && square_distance(bksq, bpsq) == 1
+ && square_rank(wksq) >= RANK_4
+ && square_distance(wksq, bpsq) - tempo > 2)
+ result = Value(80 - square_distance(wksq, bpsq) * 8);
else
- result = Value(200)
- - Value(square_distance(wksq, bpsq + DELTA_S) * 8)
- + Value(square_distance(bksq, bpsq + DELTA_S) * 8)
- + Value(square_distance(bpsq, queeningSq) * 8);
+ result = Value(200)
+ - Value(square_distance(wksq, bpsq + DELTA_S) * 8)
+ + Value(square_distance(bksq, bpsq + DELTA_S) * 8)
+ + Value(square_distance(bpsq, queeningSq) * 8);
- return (strongerSide == pos.side_to_move())? result : -result;
+ return (strongerSide == pos.side_to_move() ? result : -result);
}
-/// KR vs KB. This is very simple, and always returns drawish scores. The
+/// KR vs KB. This is very simple, and always returns drawish scores. The
/// score is slightly bigger when the defending king is close to the edge.
-
-Value KRKBEvaluationFunction::apply(const Position &pos) {
+template<>
+Value EvaluationFunction<KRKB>::apply(const Position& pos) {
assert(pos.non_pawn_material(strongerSide) == RookValueMidgame);
assert(pos.piece_count(strongerSide, PAWN) == 0);
assert(pos.piece_count(weakerSide, BISHOP) == 1);
Value result = mate_table(pos.king_square(weakerSide));
- return (pos.side_to_move() == strongerSide)? result : -result;
+ return (pos.side_to_move() == strongerSide ? result : -result);
}
/// KR vs KN. The attacking side has slightly better winning chances than
/// in KR vs KB, particularly if the king and the knight are far apart.
-
-Value KRKNEvaluationFunction::apply(const Position &pos) {
+template<>
+Value EvaluationFunction<KRKN>::apply(const Position& pos) {
assert(pos.non_pawn_material(strongerSide) == RookValueMidgame);
assert(pos.piece_count(strongerSide, PAWN) == 0);
/// defending king towards the edge. If we also take care to avoid null move
/// for the defending side in the search, this is usually sufficient to be
/// able to win KQ vs KR.
+template<>
+Value EvaluationFunction<KQKR>::apply(const Position& pos) {
-Value KQKREvaluationFunction::apply(const Position &pos) {
assert(pos.non_pawn_material(strongerSide) == QueenValueMidgame);
assert(pos.piece_count(strongerSide, PAWN) == 0);
assert(pos.non_pawn_material(weakerSide) == RookValueMidgame);
Square winnerKSq = pos.king_square(strongerSide);
Square loserKSq = pos.king_square(weakerSide);
-
- Value result = QueenValueEndgame - RookValueEndgame +
- mate_table(loserKSq) + distance_bonus(square_distance(winnerKSq, loserKSq));
+
+ Value result = QueenValueEndgame
+ - RookValueEndgame
+ + mate_table(loserKSq)
+ + distance_bonus(square_distance(winnerKSq, loserKSq));
return (strongerSide == pos.side_to_move())? result : -result;
}
+template<>
+Value EvaluationFunction<KBBKN>::apply(const Position& pos) {
-Value KBBKNEvaluationFunction::apply(const Position &pos) {
assert(pos.piece_count(strongerSide, BISHOP) == 2);
assert(pos.non_pawn_material(strongerSide) == 2*BishopValueMidgame);
assert(pos.piece_count(weakerSide, KNIGHT) == 1);
// Bonus for restricting the knight's mobility
result += Value((8 - count_1s_max_15(pos.piece_attacks<KNIGHT>(nsq))) * 8);
- return (strongerSide == pos.side_to_move())? result : -result;
+ return (strongerSide == pos.side_to_move() ? result : -result);
}
-Value KmmKmEvaluationFunction::apply(const Position &pos) {
+/// K and two minors vs K and one or two minors or K and two knights against
+/// king alone are always draw.
+template<>
+Value EvaluationFunction<KmmKm>::apply(const Position&) {
return Value(0);
}
+template<>
+Value EvaluationFunction<KNNK>::apply(const Position&) {
+ return Value(0);
+}
/// KBPKScalingFunction scales endgames where the stronger side has king,
-/// bishop and one or more pawns. It checks for draws with rook pawns and a
-/// bishop of the wrong color. If such a draw is detected, ScaleFactor(0) is
-/// returned. If not, the return value is SCALE_FACTOR_NONE, i.e. no scaling
+/// bishop and one or more pawns. It checks for draws with rook pawns and a
+/// bishop of the wrong color. If such a draw is detected, ScaleFactor(0) is
+/// returned. If not, the return value is SCALE_FACTOR_NONE, i.e. no scaling
/// will be used.
+template<>
+ScaleFactor ScalingFunction<KBPsK>::apply(const Position& pos) {
-ScaleFactor KBPKScalingFunction::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);
Bitboard pawns = pos.pawns(strongerSide);
File pawnFile = square_file(pos.piece_list(strongerSide, PAWN, 0));
- if((pawnFile == FILE_A || pawnFile == FILE_H) &&
- (pawns & ~file_bb(pawnFile)) == EmptyBoardBB) {
- // All pawns are on a single rook file.
-
- Square bishopSq = pos.piece_list(strongerSide, BISHOP, 0);
- Square queeningSq =
- relative_square(strongerSide, make_square(pawnFile, RANK_8));
- Square kingSq = pos.king_square(weakerSide);
-
- if(square_color(queeningSq) != square_color(bishopSq) &&
- file_distance(square_file(kingSq), pawnFile) <= 1) {
- // The bishop has the wrong color, and the defending king is on the
- // file of the pawn(s) or the neighboring file. Find the rank of the
- // frontmost pawn:
-
- Rank rank;
- if(strongerSide == WHITE) {
- for(rank = RANK_7; (rank_bb(rank) & pawns) == EmptyBoardBB; rank--);
- assert(rank >= RANK_2 && rank <= RANK_7);
- }
- else {
- for(rank = RANK_2; (rank_bb(rank) & pawns) == EmptyBoardBB; rank++);
- rank = Rank(rank^7); // HACK
- assert(rank >= RANK_2 && rank <= RANK_7);
+ // All pawns are on a single rook file ?
+ if ( (pawnFile == FILE_A || pawnFile == FILE_H)
+ && (pawns & ~file_bb(pawnFile)) == EmptyBoardBB)
+ {
+ Square bishopSq = pos.piece_list(strongerSide, BISHOP, 0);
+ Square queeningSq = relative_square(strongerSide, make_square(pawnFile, RANK_8));
+ Square kingSq = pos.king_square(weakerSide);
+
+ if ( square_color(queeningSq) != square_color(bishopSq)
+ && file_distance(square_file(kingSq), pawnFile) <= 1)
+ {
+ // The bishop has the wrong color, and the defending king is on the
+ // file of the pawn(s) or the neighboring file. Find the rank of the
+ // frontmost pawn.
+ Rank rank;
+ if (strongerSide == WHITE)
+ {
+ for (rank = RANK_7; (rank_bb(rank) & pawns) == EmptyBoardBB; rank--) {}
+ assert(rank >= RANK_2 && rank <= RANK_7);
+ }
+ else
+ {
+ for(rank = RANK_2; (rank_bb(rank) & pawns) == EmptyBoardBB; rank++) {}
+ rank = Rank(rank^7); // HACK to get the relative rank
+ assert(rank >= RANK_2 && rank <= RANK_7);
+ }
+ // If the defending king has distance 1 to the promotion square or
+ // is placed somewhere in front of the pawn, it's a draw.
+ if ( square_distance(kingSq, queeningSq) <= 1
+ || relative_rank(strongerSide, kingSq) >= rank)
+ return ScaleFactor(0);
}
- // If the defending king has distance 1 to the promotion square or
- // is placed somewhere in front of the pawn, it's a draw.
- if(square_distance(kingSq, queeningSq) <= 1 ||
- relative_rank(strongerSide, kingSq) >= rank)
- return ScaleFactor(0);
- }
}
return SCALE_FACTOR_NONE;
}
/// king and queen, while the weaker side has at least a rook and a pawn.
/// It tests for fortress draws with a rook on the third rank defended by
/// a pawn.
+template<>
+ScaleFactor ScalingFunction<KQKRPs>::apply(const Position& pos) {
-ScaleFactor KQKRPScalingFunction::apply(const Position &pos) {
assert(pos.non_pawn_material(strongerSide) == QueenValueMidgame);
assert(pos.piece_count(strongerSide, QUEEN) == 1);
assert(pos.piece_count(strongerSide, PAWN) == 0);
assert(pos.piece_count(weakerSide, PAWN) >= 1);
Square kingSq = pos.king_square(weakerSide);
- if(relative_rank(weakerSide, kingSq) <= RANK_2 &&
- relative_rank(weakerSide, pos.king_square(strongerSide)) >= RANK_4 &&
- (pos.rooks(weakerSide) & relative_rank_bb(weakerSide, RANK_3)) &&
- (pos.pawns(weakerSide) & relative_rank_bb(weakerSide, RANK_2)) &&
- (pos.piece_attacks<KING>(kingSq) & pos.pawns(weakerSide))) {
- Square rsq = pos.piece_list(weakerSide, ROOK, 0);
- if(pos.pawn_attacks(strongerSide, rsq) & pos.pawns(weakerSide))
- return ScaleFactor(0);
+ if ( relative_rank(weakerSide, kingSq) <= RANK_2
+ && relative_rank(weakerSide, pos.king_square(strongerSide)) >= RANK_4
+ && (pos.rooks(weakerSide) & relative_rank_bb(weakerSide, RANK_3))
+ && (pos.pawns(weakerSide) & relative_rank_bb(weakerSide, RANK_2))
+ && (pos.piece_attacks<KING>(kingSq) & pos.pawns(weakerSide)))
+ {
+ Square rsq = pos.piece_list(weakerSide, ROOK, 0);
+ if (pos.pawn_attacks(strongerSide, rsq) & pos.pawns(weakerSide))
+ return ScaleFactor(0);
}
return SCALE_FACTOR_NONE;
}
-/// KRPKRScalingFunction scales KRP vs KR endgames. This function knows a
+/// KRPKRScalingFunction scales KRP vs KR endgames. This function knows a
/// handful of the most important classes of drawn positions, but is far
-/// from perfect. It would probably be a good idea to add more knowledge
+/// from perfect. It would probably be a good idea to add more knowledge
/// in the future.
///
/// It would also be nice to rewrite the actual code for this function,
/// which is mostly copied from Glaurung 1.x, and not very pretty.
+template<>
+ScaleFactor ScalingFunction<KRPKR>::apply(const Position &pos) {
-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.
+template<>
+ScaleFactor ScalingFunction<KRPPKRP>::apply(const Position &pos) {
-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.
+template<>
+ScaleFactor ScalingFunction<KPsK>::apply(const Position &pos) {
-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.
+template<>
+ScaleFactor ScalingFunction<KBPKB>::apply(const Position &pos) {
-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))
+
+ // 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;
+}
+
+
+/// KBPPKBScalingFunction scales KBPP vs KB endgames. It detects a few basic
+/// draws with opposite-colored bishops.
+template<>
+ScaleFactor ScalingFunction<KBPPKB>::apply(const Position& pos) {
+
+ assert(pos.non_pawn_material(strongerSide) == BishopValueMidgame);
+ assert(pos.piece_count(strongerSide, BISHOP) == 1);
+ assert(pos.piece_count(strongerSide, PAWN) == 2);
+ assert(pos.non_pawn_material(weakerSide) == BishopValueMidgame);
+ assert(pos.piece_count(weakerSide, BISHOP) == 1);
+ assert(pos.piece_count(weakerSide, PAWN) == 0);
+
+ Square wbsq = pos.piece_list(strongerSide, BISHOP, 0);
+ Square bbsq = pos.piece_list(weakerSide, BISHOP, 0);
+
+ if (square_color(wbsq) == square_color(bbsq))
+ // Not opposite-colored bishops, no scaling
+ return SCALE_FACTOR_NONE;
+
+ Square ksq = pos.king_square(weakerSide);
+ Square psq1 = pos.piece_list(strongerSide, PAWN, 0);
+ Square psq2 = pos.piece_list(strongerSide, PAWN, 1);
+ Rank r1 = square_rank(psq1);
+ Rank r2 = square_rank(psq2);
+ Square blockSq1, blockSq2;
+
+ if (relative_rank(strongerSide, psq1) > relative_rank(strongerSide, psq2))
+ {
+ blockSq1 = psq1 + pawn_push(strongerSide);
+ blockSq2 = make_square(square_file(psq2), square_rank(psq1));
+ }
+ else
+ {
+ blockSq1 = psq2 + pawn_push(strongerSide);
+ blockSq2 = make_square(square_file(psq1), square_rank(psq2));
+ }
+
+ switch (file_distance(psq1, psq2))
+ {
+ case 0:
+ // Both pawns are on the same file. Easy draw if defender firmly controls
+ // some square in the frontmost pawn's path.
+ if ( square_file(ksq) == square_file(blockSq1)
+ && relative_rank(strongerSide, ksq) >= relative_rank(strongerSide, blockSq1)
+ && square_color(ksq) != square_color(wbsq))
+ return ScaleFactor(0);
+ else
+ return SCALE_FACTOR_NONE;
+
+ case 1:
+ // Pawns on neighboring files. Draw if defender firmly controls the square
+ // in front of the frontmost pawn's path, and the square diagonally behind
+ // this square on the file of the other pawn.
+ if ( ksq == blockSq1
+ && square_color(ksq) != square_color(wbsq)
+ && ( bbsq == blockSq2
+ || (pos.piece_attacks<BISHOP>(blockSq2) & pos.bishops(weakerSide))
+ || rank_distance(r1, r2) >= 2))
return ScaleFactor(0);
- if((pos.piece_attacks<BISHOP>(weakerBishopSq) & ray)
- && square_distance(weakerBishopSq, pawnSq) >= 3)
+ else if ( ksq == blockSq2
+ && square_color(ksq) != square_color(wbsq)
+ && ( bbsq == blockSq1
+ || (pos.piece_attacks<BISHOP>(blockSq1) & pos.bishops(weakerSide))))
return ScaleFactor(0);
- }
+ else
+ return SCALE_FACTOR_NONE;
+
+ default:
+ // The pawns are not on the same file or adjacent files. No scaling.
+ return SCALE_FACTOR_NONE;
}
- 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.
+template<>
+ScaleFactor ScalingFunction<KBPKN>::apply(const Position &pos) {
-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 pawnSq = pos.piece_list(strongerSide, PAWN, 0);
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.
+template<>
+ScaleFactor ScalingFunction<KNPK>::apply(const Position &pos) {
-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).
+template<>
+ScaleFactor ScalingFunction<KPKP>::apply(const Position &pos) {
-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