X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fendgame.cpp;h=dbf10582ac8964fdf3f047d6d93c54b202274c5d;hp=4d93811e7c5d15fa2fc47d1ab16e97377a448d29;hb=f21b50398231b4846c364e23bfeeab314c7731ea;hpb=f178f0a2912082e2e9d07d9b0926031322d78f67 diff --git a/src/endgame.cpp b/src/endgame.cpp index 4d93811e..5958e633 100644 --- a/src/endgame.cpp +++ b/src/endgame.cpp @@ -1,917 +1,778 @@ /* 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) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad + Copyright (C) 2015-2019 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad 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 . */ - -//// -//// Includes -//// - #include -#include "bitbase.h" +#include "bitboard.h" #include "endgame.h" +#include "movegen.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 -//// +using std::string; namespace { - // Table used to drive the defending king towards the edge of the board - // 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, + // Table used to drive the king towards the edge of the board + // in KX vs K and KQ vs KR endgames. + constexpr int PushToEdges[SQUARE_NB] = { 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, + 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: - const uint8_t KBNKMateTable[64] = { - 200, 190, 180, 170, 160, 150, 140, 130, - 190, 180, 170, 160, 150, 140, 130, 140, - 180, 170, 155, 140, 140, 125, 140, 150, - 170, 160, 140, 120, 110, 140, 150, 160, - 160, 150, 140, 110, 120, 140, 160, 170, - 150, 140, 125, 140, 140, 155, 170, 180, - 140, 130, 140, 150, 160, 170, 180, 190, - 130, 140, 150, 160, 170, 180, 190, 200 + // Table used to drive the king towards a corner square of the + // right color in KBN vs K endgames. + constexpr int PushToCorners[SQUARE_NB] = { + 6400, 6080, 5760, 5440, 5120, 4800, 4480, 4160, + 6080, 5760, 5440, 5120, 4800, 4480, 4160, 4480, + 5760, 5440, 4960, 4480, 4480, 4000, 4480, 4800, + 5440, 5120, 4480, 3840, 3520, 4480, 4800, 5120, + 5120, 4800, 4480, 3520, 3840, 4480, 5120, 5440, + 4800, 4480, 4000, 4480, 4480, 4960, 5440, 5760, + 4480, 4160, 4480, 4800, 5120, 5440, 5760, 6080, + 4160, 4480, 4800, 5120, 5440, 5760, 6080, 6400 }; - // 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}; - - // 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: - const int KRKNKingKnightDistancePenalty[8] = { 0, 0, 4, 10, 20, 32, 48, 70 }; + // Tables used to drive a piece towards or away from another piece + constexpr int PushClose[8] = { 0, 0, 100, 80, 60, 40, 20, 10 }; + constexpr int PushAway [8] = { 0, 5, 20, 40, 60, 80, 90, 100 }; - // Various inline functions for accessing the above arrays: - - inline Value mate_table(Square s) { - return Value(MateTable[s]); - } + // Pawn Rank based scaling factors used in KRPPKRP endgame + constexpr int KRPPKRPScaleFactors[RANK_NB] = { 0, 9, 10, 14, 21, 44, 0, 0 }; - inline Value kbnk_mate_table(Square s) { - return Value(KBNKMateTable[s]); +#ifndef NDEBUG + bool verify_material(const Position& pos, Color c, Value npm, int pawnsCnt) { + return pos.non_pawn_material(c) == npm && pos.count(c) == pawnsCnt; } +#endif - inline Value distance_bonus(int d) { - return Value(DistanceBonus[d]); - } + // Map the square as if strongSide is white and strongSide's only pawn + // is on the left half of the board. + Square normalize(const Position& pos, Color strongSide, Square sq) { - inline Value krkn_king_knight_distance_penalty(int d) { - return Value(KRKNKingKnightDistancePenalty[d]); - } + assert(pos.count(strongSide) == 1); - // Function for probing the KP vs K bitbase: - int probe_kpk(Square wksq, Square wpsq, Square bksq, Color stm); + if (file_of(pos.square(strongSide)) >= FILE_E) + sq = Square(sq ^ 7); // Mirror SQ_H1 -> SQ_A1 -} - - -//// -//// 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); -} + return strongSide == WHITE ? sq : ~sq; + } -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) { } +} // namespace -/// 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. +template<> +Value Endgame::operator()(const Position& pos) const { -Value KXKEvaluationFunction::apply(const Position &pos) { + assert(verify_material(pos, weakSide, VALUE_ZERO, 0)); + assert(!pos.checkers()); // Eval is never called when in check - assert(pos.non_pawn_material(weakerSide) == Value(0)); - assert(pos.piece_count(weakerSide, PAWN) == Value(0)); + // Stalemate detection with lone king + if (pos.side_to_move() == weakSide && !MoveList(pos).size()) + return VALUE_DRAW; - Square winnerKSq = pos.king_square(strongerSide); - Square loserKSq = pos.king_square(weakerSide); + Square winnerKSq = pos.square(strongSide); + Square loserKSq = pos.square(weakSide); - 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(strongSide) + + pos.count(strongSide) * PawnValueEg + + PushToEdges[loserKSq] + + PushClose[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.count(strongSide) + || pos.count(strongSide) + ||(pos.count(strongSide) && pos.count(strongSide)) + || ( (pos.pieces(strongSide, BISHOP) & ~DarkSquares) + && (pos.pieces(strongSide, BISHOP) & DarkSquares))) + result = std::min(result + VALUE_KNOWN_WIN, VALUE_MATE_IN_MAX_PLY - 1); - return (strongerSide == pos.side_to_move())? result : -result; + return strongSide == pos.side_to_move() ? result : -result; } -/// 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) { +/// Mate with KBN vs K. This is similar to KX vs K, but we have to drive the +/// defending king towards a corner square that our bishop attacks. +template<> +Value Endgame::operator()(const Position& pos) const { - 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.piece_count(strongerSide, BISHOP) == 1); - assert(pos.piece_count(strongerSide, KNIGHT) == 1); - assert(pos.piece_count(strongerSide, PAWN) == 0); + assert(verify_material(pos, strongSide, KnightValueMg + BishopValueMg, 0)); + assert(verify_material(pos, weakSide, VALUE_ZERO, 0)); - Square winnerKSq = pos.king_square(strongerSide); - Square loserKSq = pos.king_square(weakerSide); - Square bishopSquare = pos.piece_list(strongerSide, BISHOP, 0); + Square winnerKSq = pos.square(strongSide); + Square loserKSq = pos.square(weakSide); + Square bishopSq = pos.square(strongSide); - if(square_color(bishopSquare) == BLACK) { - winnerKSq = flop_square(winnerKSq); - loserKSq = flop_square(loserKSq); - } + // If our Bishop does not attack A1/H8, we flip the enemy king square + // to drive to opposite corners (A8/H1). - Value result = - VALUE_KNOWN_WIN + distance_bonus(square_distance(winnerKSq, loserKSq)) + - kbnk_mate_table(loserKSq); + Value result = VALUE_KNOWN_WIN + + PushClose[distance(winnerKSq, loserKSq)] + + PushToCorners[opposite_colors(bishopSq, SQ_A1) ? ~loserKSq : loserKSq]; - return (strongerSide == pos.side_to_move())? result : -result; + assert(abs(result) < VALUE_MATE_IN_MAX_PLY); + return strongSide == pos.side_to_move() ? result : -result; } -/// KP vs K. This endgame is evaluated with the help of a bitbase. +/// KP vs K. This endgame is evaluated with the help of a bitbase. +template<> +Value Endgame::operator()(const Position& pos) const { -Value KPKEvaluationFunction::apply(const Position &pos) { + assert(verify_material(pos, strongSide, VALUE_ZERO, 1)); + assert(verify_material(pos, weakSide, VALUE_ZERO, 0)); - 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; + // Assume strongSide is white and the pawn is on files A-D + Square wksq = normalize(pos, strongSide, pos.square(strongSide)); + Square bksq = normalize(pos, strongSide, pos.square(weakSide)); + Square psq = normalize(pos, strongSide, pos.square(strongSide)); - 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()); - } + Color us = strongSide == pos.side_to_move() ? WHITE : BLACK; - if(square_file(wpsq) >= FILE_E) { - wksq = flop_square(wksq); - bksq = flop_square(bksq); - wpsq = flop_square(wpsq); - } + if (!Bitbases::probe(wksq, psq, bksq, us)) + return VALUE_DRAW; - 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; - } + Value result = VALUE_KNOWN_WIN + PawnValueEg + Value(rank_of(psq)); - return VALUE_DRAW; + return strongSide == 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. +template<> +Value Endgame::operator()(const Position& pos) const { -Value KRKPEvaluationFunction::apply(const Position &pos) { - - assert(pos.non_pawn_material(strongerSide) == RookValueMidgame); - assert(pos.piece_count(strongerSide, PAWN) == 0); - assert(pos.non_pawn_material(weakerSide) == 0); - assert(pos.piece_count(weakerSide, PAWN) == 1); - - Square wksq, wrsq, bksq, bpsq; - int tempo = (pos.side_to_move() == strongerSide); - - wksq = pos.king_square(strongerSide); - wrsq = pos.piece_list(strongerSide, ROOK, 0); - bksq = pos.king_square(weakerSide); - bpsq = pos.piece_list(weakerSide, PAWN, 0); + assert(verify_material(pos, strongSide, RookValueMg, 0)); + assert(verify_material(pos, weakSide, VALUE_ZERO, 1)); - if(strongerSide == BLACK) { - wksq = flip_square(wksq); - wrsq = flip_square(wrsq); - bksq = flip_square(bksq); - bpsq = flip_square(bpsq); - } + Square wksq = relative_square(strongSide, pos.square(strongSide)); + Square bksq = relative_square(strongSide, pos.square(weakSide)); + Square rsq = relative_square(strongSide, pos.square(strongSide)); + Square psq = relative_square(strongSide, pos.square(weakSide)); - Square queeningSq = make_square(square_file(bpsq), RANK_1); + Square queeningSq = make_square(file_of(psq), 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 (forward_file_bb(WHITE, wksq) & psq) + result = RookValueEg - distance(wksq, psq); // 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 ( distance(bksq, psq) >= 3 + (pos.side_to_move() == weakSide) + && distance(bksq, rsq) >= 3) + result = RookValueEg - distance(wksq, psq); // 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 ( rank_of(bksq) <= RANK_3 + && distance(bksq, psq) == 1 + && rank_of(wksq) >= RANK_4 + && distance(wksq, psq) > 2 + (pos.side_to_move() == strongSide)) + result = Value(80) - 8 * distance(wksq, psq); 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) - 8 * ( distance(wksq, psq + SOUTH) + - distance(bksq, psq + SOUTH) + - distance(psq, queeningSq)); - return (strongerSide == pos.side_to_move())? result : -result; + return strongSide == 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. +template<> +Value Endgame::operator()(const Position& pos) const { -Value KRKBEvaluationFunction::apply(const Position &pos) { - - assert(pos.non_pawn_material(strongerSide) == RookValueMidgame); - assert(pos.piece_count(strongerSide, PAWN) == 0); - assert(pos.non_pawn_material(weakerSide) == BishopValueMidgame); - assert(pos.piece_count(weakerSide, PAWN) == 0); - assert(pos.piece_count(weakerSide, BISHOP) == 1); + assert(verify_material(pos, strongSide, RookValueMg, 0)); + assert(verify_material(pos, weakSide, BishopValueMg, 0)); - Value result = mate_table(pos.king_square(weakerSide)); - return (pos.side_to_move() == strongerSide)? result : -result; + Value result = Value(PushToEdges[pos.square(weakSide)]); + return strongSide == pos.side_to_move() ? result : -result; } -/// KR vs KN. The attacking side has slightly better winning chances than +/// 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. +template<> +Value Endgame::operator()(const Position& pos) const { + + assert(verify_material(pos, strongSide, RookValueMg, 0)); + assert(verify_material(pos, weakSide, KnightValueMg, 0)); + + Square bksq = pos.square(weakSide); + Square bnsq = pos.square(weakSide); + Value result = Value(PushToEdges[bksq] + PushAway[distance(bksq, bnsq)]); + return strongSide == pos.side_to_move() ? result : -result; +} -Value KRKNEvaluationFunction::apply(const Position &pos) { - assert(pos.non_pawn_material(strongerSide) == RookValueMidgame); - assert(pos.piece_count(strongerSide, PAWN) == 0); - assert(pos.non_pawn_material(weakerSide) == KnightValueMidgame); - assert(pos.piece_count(weakerSide, PAWN) == 0); - assert(pos.piece_count(weakerSide, KNIGHT) == 1); +/// KQ vs KP. In general, this is a win for the stronger side, but there are a +/// few important exceptions. A pawn on 7th rank and on the A,C,F or H files +/// with a king positioned next to it can be a draw, so in that case, we only +/// use the distance between the kings. +template<> +Value Endgame::operator()(const Position& pos) const { - Square defendingKSq = pos.king_square(weakerSide); - Square nSq = pos.piece_list(weakerSide, KNIGHT, 0); + assert(verify_material(pos, strongSide, QueenValueMg, 0)); + assert(verify_material(pos, weakSide, VALUE_ZERO, 1)); - Value result = Value(10) + mate_table(defendingKSq) + - krkn_king_knight_distance_penalty(square_distance(defendingKSq, nSq)); + Square winnerKSq = pos.square(strongSide); + Square loserKSq = pos.square(weakSide); + Square pawnSq = pos.square(weakSide); - return (strongerSide == pos.side_to_move())? result : -result; + Value result = Value(PushClose[distance(winnerKSq, loserKSq)]); + + if ( relative_rank(weakSide, pawnSq) != RANK_7 + || distance(loserKSq, pawnSq) != 1 + || !((FileABB | FileCBB | FileFBB | FileHBB) & pawnSq)) + result += QueenValueEg - PawnValueEg; + + return strongSide == pos.side_to_move() ? result : -result; } /// KQ vs KR. This is almost identical to KX vs K: We give the attacking /// king a bonus for having the kings close together, and for forcing the -/// 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. - -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); - assert(pos.piece_count(weakerSide, PAWN) == 0); - - 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)); - - return (strongerSide == pos.side_to_move())? result : -result; -} +/// 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 win KQ vs KR. +template<> +Value Endgame::operator()(const Position& pos) const { + assert(verify_material(pos, strongSide, QueenValueMg, 0)); + assert(verify_material(pos, weakSide, RookValueMg, 0)); -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); - assert(pos.non_pawn_material(weakerSide) == KnightValueMidgame); - assert(pos.pawns() == EmptyBoardBB); + Square winnerKSq = pos.square(strongSide); + Square loserKSq = pos.square(weakSide); - Value result = BishopValueEndgame; - Square wksq = pos.king_square(strongerSide); - Square bksq = pos.king_square(weakerSide); - Square nsq = pos.piece_list(weakerSide, KNIGHT, 0); + Value result = QueenValueEg + - RookValueEg + + PushToEdges[loserKSq] + + PushClose[distance(winnerKSq, loserKSq)]; - // Bonus for attacking king close to defending king - result += distance_bonus(square_distance(wksq, bksq)); + return strongSide == pos.side_to_move() ? result : -result; +} - // Bonus for driving the defending king and knight apart - result += Value(square_distance(bksq, nsq) * 32); - // Bonus for restricting the knight's mobility - result += Value((8 - count_1s_max_15(pos.piece_attacks(nsq))) * 8); +/// KNN vs KP. Simply push the opposing king to the corner +template<> +Value Endgame::operator()(const Position& pos) const { - return (strongerSide == pos.side_to_move())? result : -result; -} + assert(verify_material(pos, strongSide, 2 * KnightValueMg, 0)); + assert(verify_material(pos, weakSide, VALUE_ZERO, 1)); + Value result = 2 * KnightValueEg + - PawnValueEg + + PushToEdges[pos.square(weakSide)]; -Value KmmKmEvaluationFunction::apply(const Position &pos) { - return Value(0); + return strongSide == pos.side_to_move() ? result : -result; } -/// 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 +/// Some cases of trivial draws +template<> Value Endgame::operator()(const Position&) const { return VALUE_DRAW; } + + +/// KB and one or more pawns vs K. It checks for draws with rook pawns and +/// a bishop of the wrong color. If such a draw is detected, SCALE_FACTOR_DRAW +/// is returned. If not, the return value is SCALE_FACTOR_NONE, i.e. no scaling /// will be used. +template<> +ScaleFactor Endgame::operator()(const Position& pos) const { -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); + assert(pos.non_pawn_material(strongSide) == BishopValueMg); + assert(pos.count(strongSide) >= 1); - // No assertions about the material of weakerSide, because we want draws to + // No assertions about the material of weakSide, because we want draws to // be detected even when the weaker side has some pawns. - 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. + Bitboard pawns = pos.pieces(strongSide, PAWN); + File pawnsFile = file_of(lsb(pawns)); - Square bishopSq = pos.piece_list(strongerSide, BISHOP, 0); - Square queeningSq = - relative_square(strongerSide, make_square(pawnFile, RANK_8)); - Square kingSq = pos.king_square(weakerSide); + // All pawns are on a single rook file? + if ( (pawnsFile == FILE_A || pawnsFile == FILE_H) + && !(pawns & ~file_bb(pawnsFile))) + { + Square bishopSq = pos.square(strongSide); + Square queeningSq = relative_square(strongSide, make_square(pawnsFile, RANK_8)); + Square kingSq = pos.square(weakSide); - 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: + if ( opposite_colors(queeningSq, bishopSq) + && distance(queeningSq, kingSq) <= 1) + return SCALE_FACTOR_DRAW; + } - 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); + // If all the pawns are on the same B or G file, then it's potentially a draw + if ( (pawnsFile == FILE_B || pawnsFile == FILE_G) + && !(pos.pieces(PAWN) & ~file_bb(pawnsFile)) + && pos.non_pawn_material(weakSide) == 0 + && pos.count(weakSide) >= 1) + { + // Get weakSide pawn that is closest to the home rank + Square weakPawnSq = backmost_sq(weakSide, pos.pieces(weakSide, PAWN)); + + Square strongKingSq = pos.square(strongSide); + Square weakKingSq = pos.square(weakSide); + Square bishopSq = pos.square(strongSide); + + // There's potential for a draw if our pawn is blocked on the 7th rank, + // the bishop cannot attack it or they only have one pawn left + if ( relative_rank(strongSide, weakPawnSq) == RANK_7 + && (pos.pieces(strongSide, PAWN) & (weakPawnSq + pawn_push(weakSide))) + && (opposite_colors(bishopSq, weakPawnSq) || pos.count(strongSide) == 1)) + { + int strongKingDist = distance(weakPawnSq, strongKingSq); + int weakKingDist = distance(weakPawnSq, weakKingSq); + + // It's a draw if the weak king is on its back two ranks, within 2 + // squares of the blocking pawn and the strong king is not + // closer. (I think this rule only fails in practically + // unreachable positions such as 5k1K/6p1/6P1/8/8/3B4/8/8 w + // and positions where qsearch will immediately correct the + // problem such as 8/4k1p1/6P1/1K6/3B4/8/8/8 w) + if ( relative_rank(strongSide, weakKingSq) >= RANK_7 + && weakKingDist <= 2 + && weakKingDist <= strongKingDist) + return SCALE_FACTOR_DRAW; } - // 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; } -/// KQKRPScalingFunction scales endgames where the stronger side has only -/// 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. - -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, ROOK) == 1); - 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(kingSq) & pos.pawns(weakerSide))) { - Square rsq = pos.piece_list(weakerSide, ROOK, 0); - if(pos.pawn_attacks(strongerSide, rsq) & pos.pawns(weakerSide)) - return ScaleFactor(0); - } +/// KQ vs KR and one or more pawns. It tests for fortress draws with a rook on +/// the third rank defended by a pawn. +template<> +ScaleFactor Endgame::operator()(const Position& pos) const { + + assert(verify_material(pos, strongSide, QueenValueMg, 0)); + assert(pos.count(weakSide) == 1); + assert(pos.count(weakSide) >= 1); + + Square kingSq = pos.square(weakSide); + Square rsq = pos.square(weakSide); + + if ( relative_rank(weakSide, kingSq) <= RANK_2 + && relative_rank(weakSide, pos.square(strongSide)) >= RANK_4 + && relative_rank(weakSide, rsq) == RANK_3 + && ( pos.pieces(weakSide, PAWN) + & pos.attacks_from(kingSq) + & pos.attacks_from(rsq, strongSide))) + return SCALE_FACTOR_DRAW; + return SCALE_FACTOR_NONE; } -/// 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 -/// in the future. +/// KRP vs KR. 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 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. - -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); - assert(pos.piece_count(weakerSide, PAWN) == 0); - - Square wksq = pos.king_square(strongerSide); - Square wrsq = pos.piece_list(strongerSide, ROOK, 0); - Square wpsq = pos.piece_list(strongerSide, PAWN, 0); - Square bksq = pos.king_square(weakerSide); - 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); - } - 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); - Rank r = square_rank(wpsq); +/// which is mostly copied from Glaurung 1.x, and isn't very pretty. +template<> +ScaleFactor Endgame::operator()(const Position& pos) const { + + assert(verify_material(pos, strongSide, RookValueMg, 1)); + assert(verify_material(pos, weakSide, RookValueMg, 0)); + + // Assume strongSide is white and the pawn is on files A-D + Square wksq = normalize(pos, strongSide, pos.square(strongSide)); + Square bksq = normalize(pos, strongSide, pos.square(weakSide)); + Square wrsq = normalize(pos, strongSide, pos.square(strongSide)); + Square wpsq = normalize(pos, strongSide, pos.square(strongSide)); + Square brsq = normalize(pos, strongSide, pos.square(weakSide)); + + File f = file_of(wpsq); + Rank r = rank_of(wpsq); Square queeningSq = make_square(f, RANK_8); - int tempo = (pos.side_to_move() == strongerSide); + int tempo = (pos.side_to_move() == strongSide); // 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 + && distance(bksq, queeningSq) <= 1 + && wksq <= SQ_H5 + && (rank_of(brsq) == RANK_6 || (r <= RANK_3 && rank_of(wrsq) != RANK_6))) + return SCALE_FACTOR_DRAW; // 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 && bksq == queeningSq && square_rank(brsq) == RANK_1 && - (!tempo || square_distance(wksq, wpsq) >= 2)) - return ScaleFactor(0); + if ( r == RANK_6 + && distance(bksq, queeningSq) <= 1 + && rank_of(wksq) + tempo <= RANK_6 + && (rank_of(brsq) == RANK_1 || (!tempo && distance(brsq, wpsq) >= 3))) + return SCALE_FACTOR_DRAW; + + if ( r >= RANK_6 + && bksq == queeningSq + && rank_of(brsq) == RANK_1 + && (!tempo || distance(wksq, wpsq) >= 2)) + return SCALE_FACTOR_DRAW; // 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) + && file_of(brsq) == FILE_A + && (rank_of(brsq) <= RANK_3 || file_of(wksq) >= FILE_D || rank_of(wksq) <= RANK_5)) + return SCALE_FACTOR_DRAW; // 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 + NORTH + && distance(wksq, wpsq) - tempo >= 2 + && distance(wksq, brsq) - tempo >= 2) + return SCALE_FACTOR_DRAW; // 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))); - - // 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)); + // and the defending king cannot gain tempi by threatening the attacking rook. + if ( r == RANK_7 + && f != FILE_A + && file_of(wrsq) == f + && wrsq != queeningSq + && (distance(wksq, queeningSq) < distance(bksq, queeningSq) - 2 + tempo) + && (distance(wksq, queeningSq) < distance(bksq, wrsq) + tempo)) + return ScaleFactor(SCALE_FACTOR_MAX - 2 * distance(wksq, queeningSq)); + + // Similar to the above, but with the pawn further back + if ( f != FILE_A + && file_of(wrsq) == f + && wrsq < wpsq + && (distance(wksq, queeningSq) < distance(bksq, queeningSq) - 2 + tempo) + && (distance(wksq, wpsq + NORTH) < distance(bksq, wpsq + NORTH) - 2 + tempo) + && ( distance(bksq, wrsq) + tempo >= 3 + || ( distance(wksq, queeningSq) < distance(bksq, wrsq) + tempo + && (distance(wksq, wpsq + NORTH) < distance(bksq, wrsq) + tempo)))) + return ScaleFactor( SCALE_FACTOR_MAX + - 8 * distance(wpsq, queeningSq) + - 2 * 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 (file_of(bksq) == file_of(wpsq)) + return ScaleFactor(10); + if ( distance(bksq, wpsq) == 1 + && distance(wksq, bksq) > 2) + return ScaleFactor(24 - 2 * distance(wksq, bksq)); } - return SCALE_FACTOR_NONE; } +template<> +ScaleFactor Endgame::operator()(const Position& pos) const { + + assert(verify_material(pos, strongSide, RookValueMg, 1)); + assert(verify_material(pos, weakSide, BishopValueMg, 0)); + + // Test for a rook pawn + if (pos.pieces(PAWN) & (FileABB | FileHBB)) + { + Square ksq = pos.square(weakSide); + Square bsq = pos.square(weakSide); + Square psq = pos.square(strongSide); + Rank rk = relative_rank(strongSide, psq); + Direction push = pawn_push(strongSide); + + // If the pawn is on the 5th rank and the pawn (currently) is on + // the same color square as the bishop then there is a chance of + // a fortress. Depending on the king position give a moderate + // reduction or a stronger one if the defending king is near the + // corner but not trapped there. + if (rk == RANK_5 && !opposite_colors(bsq, psq)) + { + int d = distance(psq + 3 * push, ksq); + + if (d <= 2 && !(d == 0 && ksq == pos.square(strongSide) + 2 * push)) + return ScaleFactor(24); + else + return ScaleFactor(48); + } -/// 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. + // When the pawn has moved to the 6th rank we can be fairly sure + // it's drawn if the bishop attacks the square in front of the + // pawn from a reasonable distance and the defending king is near + // the corner + if ( rk == RANK_6 + && distance(psq + 2 * push, ksq) <= 1 + && (PseudoAttacks[BISHOP][bsq] & (psq + push)) + && distance(bsq, psq) >= 2) + return ScaleFactor(8); + } -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); - assert(pos.piece_count(weakerSide, PAWN) == 1); + return SCALE_FACTOR_NONE; +} - Square wpsq1 = pos.piece_list(strongerSide, PAWN, 0); - Square wpsq2 = pos.piece_list(strongerSide, PAWN, 1); - Square bksq = pos.king_square(weakerSide); +/// KRPP vs KRP. There is just a single rule: if the stronger side has no passed +/// pawns and the defending king is actively placed, the position is drawish. +template<> +ScaleFactor Endgame::operator()(const Position& pos) const { - // 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; + assert(verify_material(pos, strongSide, RookValueMg, 2)); + assert(verify_material(pos, weakSide, RookValueMg, 1)); - Rank r = Max(relative_rank(strongerSide, wpsq1), relative_rank(strongerSide, wpsq2)); + Square wpsq1 = pos.squares(strongSide)[0]; + Square wpsq2 = pos.squares(strongSide)[1]; + Square bksq = pos.square(weakSide); - if(file_distance(bksq, wpsq1) <= 1 && file_distance(bksq, wpsq2) <= 1 - && relative_rank(strongerSide, bksq) > r) { - switch(r) { + // Does the stronger side have a passed pawn? + if (pos.pawn_passed(strongSide, wpsq1) || pos.pawn_passed(strongSide, wpsq2)) + return SCALE_FACTOR_NONE; - 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); + Rank r = std::max(relative_rank(strongSide, wpsq1), relative_rank(strongSide, wpsq2)); - } + if ( distance(bksq, wpsq1) <= 1 + && distance(bksq, wpsq2) <= 1 + && relative_rank(strongSide, bksq) > r) + { + assert(r > RANK_1 && r < RANK_7); + return ScaleFactor(KRPPKRPScaleFactors[r]); } 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 -/// the same rook file and are blocked by the defending king, it's a draw. +/// K and two or more pawns vs K. 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 Endgame::operator()(const Position& pos) const { -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)); - assert(pos.piece_count(weakerSide, PAWN) == 0); + assert(pos.non_pawn_material(strongSide) == VALUE_ZERO); + assert(pos.count(strongSide) >= 2); + assert(verify_material(pos, weakSide, VALUE_ZERO, 0)); - Bitboard pawns = pos.pawns(strongerSide); + Square ksq = pos.square(weakSide); + Bitboard pawns = pos.pieces(strongSide, PAWN); - // 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; - } - // Are all pawns on the 'h' file? - 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); - else + // If all pawns are ahead of the king, on a single rook file and + // the king is within one file of the pawns, it's a draw. + if ( !(pawns & ~forward_ranks_bb(weakSide, ksq)) + && !((pawns & ~FileABB) && (pawns & ~FileHBB)) + && distance(ksq, lsb(pawns)) <= 1) + return SCALE_FACTOR_DRAW; + + return SCALE_FACTOR_NONE; +} + + +/// KBP vs KB. 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 a draw. +template<> +ScaleFactor Endgame::operator()(const Position& pos) const { + + assert(verify_material(pos, strongSide, BishopValueMg, 1)); + assert(verify_material(pos, weakSide, BishopValueMg, 0)); + + Square pawnSq = pos.square(strongSide); + Square strongBishopSq = pos.square(strongSide); + Square weakBishopSq = pos.square(weakSide); + Square weakKingSq = pos.square(weakSide); + + // Case 1: Defending king blocks the pawn, and cannot be driven away + if ( file_of(weakKingSq) == file_of(pawnSq) + && relative_rank(strongSide, pawnSq) < relative_rank(strongSide, weakKingSq) + && ( opposite_colors(weakKingSq, strongBishopSq) + || relative_rank(strongSide, weakKingSq) <= RANK_6)) + return SCALE_FACTOR_DRAW; + + // Case 2: Opposite colored bishops + if (opposite_colors(strongBishopSq, weakBishopSq)) + return SCALE_FACTOR_DRAW; + + return SCALE_FACTOR_NONE; +} + + +/// KBPP vs KB. It detects a few basic draws with opposite-colored bishops +template<> +ScaleFactor Endgame::operator()(const Position& pos) const { + + assert(verify_material(pos, strongSide, BishopValueMg, 2)); + assert(verify_material(pos, weakSide, BishopValueMg, 0)); + + Square wbsq = pos.square(strongSide); + Square bbsq = pos.square(weakSide); + + if (!opposite_colors(wbsq, bbsq)) return SCALE_FACTOR_NONE; + + Square ksq = pos.square(weakSide); + Square psq1 = pos.squares(strongSide)[0]; + Square psq2 = pos.squares(strongSide)[1]; + Square blockSq1, blockSq2; + + if (relative_rank(strongSide, psq1) > relative_rank(strongSide, psq2)) + { + blockSq1 = psq1 + pawn_push(strongSide); + blockSq2 = make_square(file_of(psq2), rank_of(psq1)); } else - return SCALE_FACTOR_NONE; -} + { + blockSq1 = psq2 + pawn_push(strongSide); + blockSq2 = make_square(file_of(psq1), rank_of(psq2)); + } + switch (distance(psq1, psq2)) + { + case 0: + // Both pawns are on the same file. It's an easy draw if the defender firmly + // controls some square in the frontmost pawn's path. + if ( file_of(ksq) == file_of(blockSq1) + && relative_rank(strongSide, ksq) >= relative_rank(strongSide, blockSq1) + && opposite_colors(ksq, wbsq)) + return SCALE_FACTOR_DRAW; + else + return SCALE_FACTOR_NONE; + + case 1: + // Pawns on adjacent files. It's a draw if the 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 + && opposite_colors(ksq, wbsq) + && ( bbsq == blockSq2 + || (pos.attacks_from(blockSq2) & pos.pieces(weakSide, BISHOP)) + || distance(psq1, psq2) >= 2)) + return SCALE_FACTOR_DRAW; + + else if ( ksq == blockSq2 + && opposite_colors(ksq, wbsq) + && ( bbsq == blockSq1 + || (pos.attacks_from(blockSq1) & pos.pieces(weakSide, BISHOP)))) + return SCALE_FACTOR_DRAW; + else + return SCALE_FACTOR_NONE; -/// 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 -/// 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); - assert(pos.non_pawn_material(weakerSide) == BishopValueMidgame); - assert(pos.piece_count(weakerSide, BISHOP) == 1); - assert(pos.piece_count(weakerSide, PAWN) == 0); - - Square pawnSq = pos.piece_list(strongerSide, PAWN, 0); - Square strongerBishopSq = pos.piece_list(strongerSide, BISHOP, 0); - 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) - 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(weakerBishopSq) & ray) - && square_distance(weakerBishopSq, pawnSq) >= 3) - return ScaleFactor(0); - } + 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: -/// 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); - assert(pos.non_pawn_material(weakerSide) == KnightValueMidgame); - assert(pos.piece_count(weakerSide, KNIGHT) == 1); - assert(pos.piece_count(weakerSide, PAWN) == 0); - - 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); +/// KBP vs KN. 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 Endgame::operator()(const Position& pos) const { + + assert(verify_material(pos, strongSide, BishopValueMg, 1)); + assert(verify_material(pos, weakSide, KnightValueMg, 0)); + + Square pawnSq = pos.square(strongSide); + Square strongBishopSq = pos.square(strongSide); + Square weakKingSq = pos.square(weakSide); + + if ( file_of(weakKingSq) == file_of(pawnSq) + && relative_rank(strongSide, pawnSq) < relative_rank(strongSide, weakKingSq) + && ( opposite_colors(weakKingSq, strongBishopSq) + || relative_rank(strongSide, weakKingSq) <= RANK_6)) + return SCALE_FACTOR_DRAW; return SCALE_FACTOR_NONE; } -/// 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); - assert(pos.non_pawn_material(weakerSide) == Value(0)); - assert(pos.piece_count(weakerSide, PAWN) == 0); +/// KNP vs K. 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 Endgame::operator()(const Position& pos) const { - Square pawnSq = pos.piece_list(strongerSide, PAWN, 0); - Square weakerKingSq = pos.king_square(weakerSide); + assert(verify_material(pos, strongSide, KnightValueMg, 1)); + assert(verify_material(pos, weakSide, VALUE_ZERO, 0)); - if(pawnSq == relative_square(strongerSide, SQ_A7) && - square_distance(weakerKingSq, relative_square(strongerSide, SQ_A8)) <= 1) - return ScaleFactor(0); + // Assume strongSide is white and the pawn is on files A-D + Square pawnSq = normalize(pos, strongSide, pos.square(strongSide)); + Square weakKingSq = normalize(pos, strongSide, pos.square(weakSide)); - if(pawnSq == relative_square(strongerSide, SQ_H7) && - square_distance(weakerKingSq, relative_square(strongerSide, SQ_H8)) <= 1) - return ScaleFactor(0); + if (pawnSq == SQ_A7 && distance(SQ_A8, weakKingSq) <= 1) + return SCALE_FACTOR_DRAW; 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 -/// 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 -/// 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). +/// KNP vs KB. If knight can block bishop from taking pawn, it's a win. +/// Otherwise the position is drawn. +template<> +ScaleFactor Endgame::operator()(const Position& pos) const { -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); - assert(pos.piece_count(BLACK, PAWN) == 1); + assert(verify_material(pos, strongSide, KnightValueMg, 1)); + assert(verify_material(pos, weakSide, BishopValueMg, 0)); - Square wksq, bksq, wpsq; - Color stm; + Square pawnSq = pos.square(strongSide); + Square bishopSq = pos.square(weakSide); + Square weakKingSq = pos.square(weakSide); - 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()); - } + // King needs to get close to promoting pawn to prevent knight from blocking. + // Rules for this are very tricky, so just approximate. + if (forward_file_bb(strongSide, pawnSq) & pos.attacks_from(bishopSq)) + return ScaleFactor(distance(weakKingSq, pawnSq)); - 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; - - // 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; - else - return ScaleFactor(0); + return SCALE_FACTOR_NONE; } -/// init_bitbases() is called during program initialization, and simply loads -/// bitbases from disk into memory. At the moment, there is only the bitbase -/// for KP vs K, but we may decide to add other bitbases later. +/// KP vs KP. 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, it probably +/// has at least a draw with 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 Endgame::operator()(const Position& pos) const { -void init_bitbases() { - generate_kpk_bitbase(KPKBitbase); -} + assert(verify_material(pos, strongSide, VALUE_ZERO, 1)); + assert(verify_material(pos, weakSide, VALUE_ZERO, 1)); + // Assume strongSide is white and the pawn is on files A-D + Square wksq = normalize(pos, strongSide, pos.square(strongSide)); + Square bksq = normalize(pos, strongSide, pos.square(weakSide)); + Square psq = normalize(pos, strongSide, pos.square(strongSide)); -namespace { + Color us = strongSide == pos.side_to_move() ? WHITE : BLACK; - // Probe the KP vs K bitbase: + // 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 (rank_of(psq) >= RANK_5 && file_of(psq) != FILE_A) + return SCALE_FACTOR_NONE; - 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)); - } - + // 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. + return Bitbases::probe(wksq, psq, bksq, us) ? SCALE_FACTOR_NONE : SCALE_FACTOR_DRAW; }