X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fendgame.cpp;h=a8c1e1d01ffb4d4803fbc1a957bd25366a2b85a7;hp=f9bec0aaca7fd1d257d9632c8027cfe2e514d3b9;hb=297c12e595ebc33e11be73ee4b188326418acb4f;hpb=ec2927286a7bd3cb6ae68a4f3feaee1036b8196d diff --git a/src/endgame.cpp b/src/endgame.cpp index f9bec0aa..a8c1e1d0 100644 --- a/src/endgame.cpp +++ b/src/endgame.cpp @@ -1,7 +1,7 @@ /* 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 @@ -25,90 +25,10 @@ #include #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 //// @@ -179,44 +99,12 @@ namespace { //// 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 /// 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::apply(const Position& pos) { assert(pos.non_pawn_material(weakerSide) == Value(0)); assert(pos.piece_count(weakerSide, PAWN) == Value(0)); @@ -241,8 +129,8 @@ Value KXKEvaluationFunction::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 of the right color. - -Value KBNKEvaluationFunction::apply(const Position& pos) { +template<> +Value EvaluationFunction::apply(const Position& pos) { assert(pos.non_pawn_material(weakerSide) == Value(0)); assert(pos.piece_count(weakerSide, PAWN) == Value(0)); @@ -270,8 +158,8 @@ Value KBNKEvaluationFunction::apply(const Position& pos) { /// KP vs K. This endgame is evaluated with the help of a bitbase. - -Value KPKEvaluationFunction::apply(const Position& pos) { +template<> +Value EvaluationFunction::apply(const Position& pos) { assert(pos.non_pawn_material(strongerSide) == Value(0)); assert(pos.non_pawn_material(weakerSide) == Value(0)); @@ -318,8 +206,8 @@ Value KPKEvaluationFunction::apply(const Position& pos) { /// 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::apply(const Position& pos) { assert(pos.non_pawn_material(strongerSide) == RookValueMidgame); assert(pos.piece_count(strongerSide, PAWN) == 0); @@ -375,8 +263,8 @@ Value KRKPEvaluationFunction::apply(const Position& pos) { /// 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::apply(const Position& pos) { assert(pos.non_pawn_material(strongerSide) == RookValueMidgame); assert(pos.piece_count(strongerSide, PAWN) == 0); @@ -391,8 +279,8 @@ Value KRKBEvaluationFunction::apply(const Position& pos) { /// 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::apply(const Position& pos) { assert(pos.non_pawn_material(strongerSide) == RookValueMidgame); assert(pos.piece_count(strongerSide, PAWN) == 0); @@ -415,8 +303,8 @@ Value KRKNEvaluationFunction::apply(const Position& pos) { /// 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) { +template<> +Value EvaluationFunction::apply(const Position& pos) { assert(pos.non_pawn_material(strongerSide) == QueenValueMidgame); assert(pos.piece_count(strongerSide, PAWN) == 0); @@ -434,8 +322,8 @@ Value KQKREvaluationFunction::apply(const Position& pos) { return (strongerSide == pos.side_to_move())? result : -result; } - -Value KBBKNEvaluationFunction::apply(const Position& pos) { +template<> +Value EvaluationFunction::apply(const Position& pos) { assert(pos.piece_count(strongerSide, BISHOP) == 2); assert(pos.non_pawn_material(strongerSide) == 2*BishopValueMidgame); @@ -460,8 +348,8 @@ Value KBBKNEvaluationFunction::apply(const Position& pos) { return (strongerSide == pos.side_to_move() ? result : -result); } - -Value KmmKmEvaluationFunction::apply(const Position &pos) { +template<> +Value EvaluationFunction::apply(const Position&) { return Value(0); } @@ -471,8 +359,8 @@ Value KmmKmEvaluationFunction::apply(const Position &pos) { /// 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. - -ScaleFactor KBPKScalingFunction::apply(const Position& pos) { +template<> +ScaleFactor ScalingFunction::apply(const Position& pos) { assert(pos.non_pawn_material(strongerSide) == BishopValueMidgame); assert(pos.piece_count(strongerSide, BISHOP) == 1); @@ -526,8 +414,8 @@ ScaleFactor KBPKScalingFunction::apply(const Position& pos) { /// 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) { +template<> +ScaleFactor ScalingFunction::apply(const Position& pos) { assert(pos.non_pawn_material(strongerSide) == QueenValueMidgame); assert(pos.piece_count(strongerSide, QUEEN) == 1); @@ -557,8 +445,9 @@ ScaleFactor KQKRPScalingFunction::apply(const Position& pos) { /// /// 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::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); @@ -571,20 +460,22 @@ ScaleFactor KRPKRScalingFunction::apply(const Position &pos) { 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); @@ -593,87 +484,88 @@ ScaleFactor KRPKRScalingFunction::apply(const Position &pos) { 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::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); @@ -684,34 +576,35 @@ ScaleFactor KRPPKRPScalingFunction::apply(const Position &pos) { 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::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)); @@ -720,41 +613,44 @@ ScaleFactor KPsKScalingFunction::apply(const Position &pos) { 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::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); @@ -767,48 +663,123 @@ ScaleFactor KBPKBScalingFunction::apply(const Position &pos) { 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(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::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(blockSq2) & pos.bishops(weakerSide)) + || rank_distance(r1, r2) >= 2)) return ScaleFactor(0); - if((pos.piece_attacks(weakerBishopSq) & ray) - && square_distance(weakerBishopSq, pawnSq) >= 3) + else if ( ksq == blockSq2 + && square_color(ksq) != square_color(wbsq) + && ( bbsq == blockSq1 + || (pos.piece_attacks(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::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); @@ -820,21 +791,22 @@ ScaleFactor KBPKNScalingFunction::apply(const Position &pos) { Square strongerBishopSq = pos.piece_list(strongerSide, BISHOP, 0); Square weakerKingSq = pos.king_square(weakerSide); - if(square_file(weakerKingSq) == square_file(pawnSq) - && relative_rank(strongerSide, pawnSq) < relative_rank(strongerSide, weakerKingSq) - && (square_color(weakerKingSq) != square_color(strongerBishopSq) - || relative_rank(strongerSide, weakerKingSq) <= RANK_6)) - return ScaleFactor(0); + if ( square_file(weakerKingSq) == square_file(pawnSq) + && relative_rank(strongerSide, pawnSq) < relative_rank(strongerSide, weakerKingSq) + && ( square_color(weakerKingSq) != square_color(strongerBishopSq) + || relative_rank(strongerSide, weakerKingSq) <= RANK_6)) + return ScaleFactor(0); return SCALE_FACTOR_NONE; } -/// KNPKScalingFunction scales KNP vs K endgames. There is a single rule: +/// KNPKScalingFunction scales KNP vs K endgames. There is a single rule: /// If the pawn is a rook pawn on the 7th rank and the defending king prevents /// the pawn from advancing, the position is drawn. +template<> +ScaleFactor ScalingFunction::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); @@ -844,26 +816,27 @@ ScaleFactor KNPKScalingFunction::apply(const Position &pos) { Square pawnSq = pos.piece_list(strongerSide, PAWN, 0); Square weakerKingSq = pos.king_square(weakerSide); - if(pawnSq == relative_square(strongerSide, SQ_A7) && - square_distance(weakerKingSq, relative_square(strongerSide, SQ_A8)) <= 1) - return ScaleFactor(0); + if ( pawnSq == relative_square(strongerSide, SQ_A7) + && square_distance(weakerKingSq, relative_square(strongerSide, SQ_A8)) <= 1) + return ScaleFactor(0); - if(pawnSq == relative_square(strongerSide, SQ_H7) && - square_distance(weakerKingSq, relative_square(strongerSide, SQ_H8)) <= 1) - return ScaleFactor(0); + if ( pawnSq == relative_square(strongerSide, SQ_H7) + && square_distance(weakerKingSq, relative_square(strongerSide, SQ_H8)) <= 1) + return ScaleFactor(0); return SCALE_FACTOR_NONE; } -/// KPKPScalingFunction scales KP vs KP endgames. This is done by removing -/// the weakest side's pawn and probing the KP vs K bitbase: If the weakest +/// KPKPScalingFunction scales KP vs KP endgames. This is done by removing +/// the weakest side's pawn and probing the KP vs K bitbase: If the weakest /// side has a draw without the pawn, she probably has at least a draw with -/// the pawn as well. The exception is when the stronger side's pawn is far +/// the pawn as well. The exception is when the stronger side's pawn is far /// advanced and not on a rook file; in this case it is often possible to win /// (e.g. 8/4k3/3p4/3P4/6K1/8/8/8 w - - 0 1). +template<> +ScaleFactor ScalingFunction::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); @@ -872,36 +845,40 @@ ScaleFactor KPKPScalingFunction::apply(const Position &pos) { Square wksq, bksq, wpsq; Color stm; - if(strongerSide == WHITE) { - wksq = pos.king_square(WHITE); - bksq = pos.king_square(BLACK); - wpsq = pos.piece_list(WHITE, PAWN, 0); - stm = pos.side_to_move(); + if (strongerSide == WHITE) + { + wksq = pos.king_square(WHITE); + bksq = pos.king_square(BLACK); + wpsq = pos.piece_list(WHITE, PAWN, 0); + stm = pos.side_to_move(); } - else { - wksq = flip_square(pos.king_square(BLACK)); - bksq = flip_square(pos.king_square(WHITE)); - wpsq = flip_square(pos.piece_list(BLACK, PAWN, 0)); - stm = opposite_color(pos.side_to_move()); + else + { + wksq = flip_square(pos.king_square(BLACK)); + bksq = flip_square(pos.king_square(WHITE)); + wpsq = flip_square(pos.piece_list(BLACK, PAWN, 0)); + stm = opposite_color(pos.side_to_move()); } - if(square_file(wpsq) >= FILE_E) { - wksq = flop_square(wksq); - bksq = flop_square(bksq); - wpsq = flop_square(wpsq); + if (square_file(wpsq) >= FILE_E) + { + wksq = flop_square(wksq); + bksq = flop_square(bksq); + wpsq = flop_square(wpsq); } // If the pawn has advanced to the fifth rank or further, and is not a // rook pawn, it's too dangerous to assume that it's at least a draw. - if(square_rank(wpsq) >= RANK_5 && square_file(wpsq) != FILE_A) - return SCALE_FACTOR_NONE; + if ( square_rank(wpsq) >= RANK_5 + && square_file(wpsq) != FILE_A) + return SCALE_FACTOR_NONE; - // Probe the KPK bitbase with the weakest side's pawn removed. If it's a + // Probe the KPK bitbase with the weakest side's pawn removed. If it's a // draw, it's probably at least a draw even with the pawn. - if(probe_kpk(wksq, wpsq, bksq, stm)) - return SCALE_FACTOR_NONE; + if (probe_kpk(wksq, wpsq, bksq, stm)) + return SCALE_FACTOR_NONE; else - return ScaleFactor(0); + return ScaleFactor(0); } @@ -919,11 +896,11 @@ namespace { // Probe the KP vs K bitbase: int probe_kpk(Square wksq, Square wpsq, Square bksq, Color stm) { + int wp = int(square_file(wpsq)) + (int(square_rank(wpsq)) - 1) * 4; int index = int(stm) + 2*int(bksq) + 128*int(wksq) + 8192*wp; assert(index >= 0 && index < 24576*8); return KPKBitbase[index/8] & (1 << (index&7)); } - }