X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fendgame.cpp;h=24c8c5d41c344dd3cd501d6e955024eb7988ff17;hp=f9bec0aaca7fd1d257d9632c8027cfe2e514d3b9;hb=ea2b8a93eb3cf2765e51d33ecf37c3994eacb84d;hpb=ec2927286a7bd3cb6ae68a4f3feaee1036b8196d diff --git a/src/endgame.cpp b/src/endgame.cpp index f9bec0aa..24c8c5d4 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) 2008-2010 Marco Costalba, Joona Kiiski, 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 @@ -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 //// @@ -145,13 +65,13 @@ namespace { // 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 }; + // Bitbase for KP vs K + uint8_t KPKBitbase[24576]; + // Various inline functions for accessing the above arrays inline Value mate_table(Square s) { return Value(MateTable[s]); @@ -179,44 +99,21 @@ 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) {} - +/// 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. -ScalingFunction::ScalingFunction(Color c) : strongerSide(c) { - weakerSide = opposite_color(c); +void init_bitbases() { + generate_kpk_bitbase(KPKBitbase); } -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) const { assert(pos.non_pawn_material(weakerSide) == Value(0)); assert(pos.piece_count(weakerSide, PAWN) == Value(0)); @@ -229,20 +126,20 @@ Value KXKEvaluationFunction::apply(const Position& pos) { + mate_table(loserKSq) + distance_bonus(square_distance(winnerKSq, loserKSq)); - if ( pos.piece_count(strongerSide, QUEEN) > 0 - || pos.piece_count(strongerSide, ROOK) > 0 + if ( pos.piece_count(strongerSide, QUEEN) + || pos.piece_count(strongerSide, ROOK) || pos.piece_count(strongerSide, BISHOP) > 1) // TODO: check for two equal-colored bishops! result += VALUE_KNOWN_WIN; - return (strongerSide == pos.side_to_move() ? result : -result); + return strongerSide == pos.side_to_move() ? result : -result; } /// Mate with KBN vs K. This is similar to KX vs K, but we have to drive the /// defending king towards a corner square of the right color. - -Value KBNKEvaluationFunction::apply(const Position& pos) { +template<> +Value EvaluationFunction::apply(const Position& pos) const { assert(pos.non_pawn_material(weakerSide) == Value(0)); assert(pos.piece_count(weakerSide, PAWN) == Value(0)); @@ -255,7 +152,10 @@ Value KBNKEvaluationFunction::apply(const Position& pos) { Square loserKSq = pos.king_square(weakerSide); Square bishopSquare = pos.piece_list(strongerSide, BISHOP, 0); - if (square_color(bishopSquare) == BLACK) + // kbnk_mate_table() tries to drive toward corners A1 or H8, + // if we have a bishop that cannot reach the above squares we + // mirror the kings so to drive enemy toward corners A8 or H1. + if (!same_color_squares(bishopSquare, SQ_A1)) { winnerKSq = flop_square(winnerKSq); loserKSq = flop_square(loserKSq); @@ -265,13 +165,13 @@ Value KBNKEvaluationFunction::apply(const Position& pos) { + distance_bonus(square_distance(winnerKSq, loserKSq)) + kbnk_mate_table(loserKSq); - return (strongerSide == pos.side_to_move() ? result : -result); + return strongerSide == pos.side_to_move() ? result : -result; } /// KP vs K. This endgame is evaluated with the help of a bitbase. - -Value KPKEvaluationFunction::apply(const Position& pos) { +template<> +Value EvaluationFunction::apply(const Position& pos) const { assert(pos.non_pawn_material(strongerSide) == Value(0)); assert(pos.non_pawn_material(weakerSide) == Value(0)); @@ -298,9 +198,9 @@ Value KPKEvaluationFunction::apply(const Position& pos) { if (square_file(wpsq) >= FILE_E) { - wksq = flop_square(wksq); - bksq = flop_square(bksq); - wpsq = flop_square(wpsq); + wksq = flop_square(wksq); + bksq = flop_square(bksq); + wpsq = flop_square(wpsq); } if (!probe_kpk(wksq, wpsq, bksq, stm)) @@ -310,7 +210,7 @@ Value KPKEvaluationFunction::apply(const Position& pos) { + PawnValueEndgame + Value(square_rank(wpsq)); - return (strongerSide == pos.side_to_move() ? result : -result); + return strongerSide == pos.side_to_move() ? result : -result; } @@ -318,8 +218,8 @@ 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) const { assert(pos.non_pawn_material(strongerSide) == RookValueMidgame); assert(pos.piece_count(strongerSide, PAWN) == 0); @@ -351,7 +251,7 @@ Value KRKPEvaluationFunction::apply(const Position& pos) { // 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 + else if ( square_distance(bksq, bpsq) - (tempo ^ 1) >= 3 && square_distance(bksq, wrsq) >= 3) result = RookValueEndgame - Value(square_distance(wksq, bpsq)); @@ -369,14 +269,14 @@ Value KRKPEvaluationFunction::apply(const Position& pos) { + Value(square_distance(bksq, bpsq + DELTA_S) * 8) + Value(square_distance(bpsq, queeningSq) * 8); - return (strongerSide == pos.side_to_move() ? result : -result); + return strongerSide == pos.side_to_move() ? result : -result; } /// KR vs KB. This is very simple, and always returns drawish scores. The /// 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) const { assert(pos.non_pawn_material(strongerSide) == RookValueMidgame); assert(pos.piece_count(strongerSide, PAWN) == 0); @@ -385,14 +285,14 @@ Value KRKBEvaluationFunction::apply(const Position& pos) { assert(pos.piece_count(weakerSide, BISHOP) == 1); Value result = mate_table(pos.king_square(weakerSide)); - return (pos.side_to_move() == strongerSide ? result : -result); + return strongerSide == pos.side_to_move() ? result : -result; } /// KR vs KN. The attacking side has slightly better winning chances than /// in KR vs KB, particularly if the king and the knight are far apart. - -Value KRKNEvaluationFunction::apply(const Position& pos) { +template<> +Value EvaluationFunction::apply(const Position& pos) const { assert(pos.non_pawn_material(strongerSide) == RookValueMidgame); assert(pos.piece_count(strongerSide, PAWN) == 0); @@ -403,10 +303,12 @@ Value KRKNEvaluationFunction::apply(const Position& pos) { Square defendingKSq = pos.king_square(weakerSide); Square nSq = pos.piece_list(weakerSide, KNIGHT, 0); - Value result = Value(10) + mate_table(defendingKSq) + - krkn_king_knight_distance_penalty(square_distance(defendingKSq, nSq)); + int d = square_distance(defendingKSq, nSq); + Value result = Value(10) + + mate_table(defendingKSq) + + krkn_king_knight_distance_penalty(d); - return (strongerSide == pos.side_to_move())? result : -result; + return strongerSide == pos.side_to_move() ? result : -result; } @@ -415,8 +317,8 @@ 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) const { assert(pos.non_pawn_material(strongerSide) == QueenValueMidgame); assert(pos.piece_count(strongerSide, PAWN) == 0); @@ -431,17 +333,17 @@ Value KQKREvaluationFunction::apply(const Position& pos) { + mate_table(loserKSq) + distance_bonus(square_distance(winnerKSq, loserKSq)); - return (strongerSide == pos.side_to_move())? result : -result; + return strongerSide == pos.side_to_move() ? result : -result; } - -Value KBBKNEvaluationFunction::apply(const Position& pos) { +template<> +Value EvaluationFunction::apply(const Position& pos) const { 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); + assert(pos.pieces(PAWN) == EmptyBoardBB); Value result = BishopValueEndgame; Square wksq = pos.king_square(strongerSide); @@ -455,24 +357,31 @@ Value KBBKNEvaluationFunction::apply(const Position& pos) { 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); + result += Value((8 - count_1s_max_15(pos.attacks_from(nsq))) * 8); - return (strongerSide == pos.side_to_move() ? result : -result); + return strongerSide == pos.side_to_move() ? result : -result; } -Value KmmKmEvaluationFunction::apply(const Position &pos) { +/// K and two minors vs K and one or two minors or K and two knights against +/// king alone are always draw. +template<> +Value EvaluationFunction::apply(const Position&) const { return Value(0); } +template<> +Value EvaluationFunction::apply(const Position&) const { + return Value(0); +} /// KBPKScalingFunction scales endgames where the stronger side has king, /// bishop and one or more pawns. It checks for draws with rook pawns and a -/// bishop of the wrong color. If such a draw is detected, ScaleFactor(0) is +/// bishop of the wrong color. If such a draw is detected, SCALE_FACTOR_ZERO 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) const { assert(pos.non_pawn_material(strongerSide) == BishopValueMidgame); assert(pos.piece_count(strongerSide, BISHOP) == 1); @@ -481,7 +390,7 @@ ScaleFactor KBPKScalingFunction::apply(const Position& pos) { // No assertions about the material of weakerSide, because we want draws to // be detected even when the weaker side has some pawns. - Bitboard pawns = pos.pawns(strongerSide); + Bitboard pawns = pos.pieces(PAWN, strongerSide); File pawnFile = square_file(pos.piece_list(strongerSide, PAWN, 0)); // All pawns are on a single rook file ? @@ -492,13 +401,12 @@ ScaleFactor KBPKScalingFunction::apply(const Position& pos) { Square queeningSq = relative_square(strongerSide, make_square(pawnFile, RANK_8)); Square kingSq = pos.king_square(weakerSide); - if ( square_color(queeningSq) != square_color(bishopSq) + if ( !same_color_squares(queeningSq, bishopSq) && file_distance(square_file(kingSq), pawnFile) <= 1) { // The bishop has the wrong color, and the defending king is on the // file of the pawn(s) or the neighboring file. Find the rank of the // frontmost pawn. - Rank rank; if (strongerSide == WHITE) { @@ -507,15 +415,15 @@ ScaleFactor KBPKScalingFunction::apply(const Position& pos) { } else { - for(rank = RANK_2; (rank_bb(rank) & pawns) == EmptyBoardBB; rank++) {} - rank = Rank(rank^7); // HACK to get the relative rank + for (rank = RANK_2; (rank_bb(rank) & pawns) == EmptyBoardBB; rank++) {} + rank = Rank(rank ^ 7); // HACK to get the relative rank assert(rank >= RANK_2 && rank <= RANK_7); } // If the defending king has distance 1 to the promotion square or // is placed somewhere in front of the pawn, it's a draw. if ( square_distance(kingSq, queeningSq) <= 1 || relative_rank(strongerSide, kingSq) >= rank) - return ScaleFactor(0); + return SCALE_FACTOR_ZERO; } } return SCALE_FACTOR_NONE; @@ -526,8 +434,8 @@ 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) const { assert(pos.non_pawn_material(strongerSide) == QueenValueMidgame); assert(pos.piece_count(strongerSide, QUEEN) == 1); @@ -538,13 +446,13 @@ ScaleFactor KQKRPScalingFunction::apply(const Position& pos) { 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))) + && (pos.pieces(ROOK, weakerSide) & relative_rank_bb(weakerSide, RANK_3)) + && (pos.pieces(PAWN, weakerSide) & relative_rank_bb(weakerSide, RANK_2)) + && (pos.attacks_from(kingSq) & pos.pieces(PAWN, weakerSide))) { Square rsq = pos.piece_list(weakerSide, ROOK, 0); - if (pos.pawn_attacks(strongerSide, rsq) & pos.pawns(weakerSide)) - return ScaleFactor(0); + if (pos.attacks_from(rsq, strongerSide) & pos.pieces(PAWN, weakerSide)) + return SCALE_FACTOR_ZERO; } return SCALE_FACTOR_NONE; } @@ -557,8 +465,9 @@ 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) const { -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 +480,22 @@ 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 +504,88 @@ 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 SCALE_FACTOR_ZERO; // 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 + && square_distance(bksq, queeningSq) <= 1 + && square_rank(wksq) + tempo <= RANK_6 + && (square_rank(brsq) == RANK_1 || (!tempo && abs(square_file(brsq) - f) >= 3))) + return SCALE_FACTOR_ZERO; + + if ( r >= RANK_6 + && bksq == queeningSq + && square_rank(brsq) == RANK_1 + && (!tempo || square_distance(wksq, wpsq) >= 2)) + return SCALE_FACTOR_ZERO; // 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 SCALE_FACTOR_ZERO; // 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 SCALE_FACTOR_ZERO; // 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) const { -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); @@ -684,77 +596,73 @@ 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) 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); - Bitboard pawns = pos.pawns(strongerSide); + Square ksq = pos.king_square(weakerSide); + Bitboard pawns = pos.pieces(PAWN, 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? + if ( square_distance(ksq, relative_square(strongerSide, SQ_A8)) <= 1 + || ( square_file(ksq) == FILE_A + && (in_front_bb(strongerSide, ksq) & pawns) == EmptyBoardBB)) + return SCALE_FACTOR_ZERO; } // 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); - else - return SCALE_FACTOR_NONE; + if ( square_distance(ksq, relative_square(strongerSide, SQ_H8)) <= 1 + || ( square_file(ksq) == FILE_H + && (in_front_bb(strongerSide, ksq) & pawns) == EmptyBoardBB)) + return SCALE_FACTOR_ZERO; } - 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) const { -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 +675,125 @@ 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) - 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); - } + // 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) + && ( !same_color_squares(weakerKingSq, strongerBishopSq) + || relative_rank(strongerSide, weakerKingSq) <= RANK_6)) + return SCALE_FACTOR_ZERO; + + // Case 2: Opposite colored bishops + if (!same_color_squares(strongerBishopSq, 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 SCALE_FACTOR_ZERO; + else + { + Bitboard ray = ray_bb(pawnSq, (strongerSide == WHITE)? SIGNED_DIR_N : SIGNED_DIR_S); + if (ray & pos.pieces(KING, weakerSide)) + return SCALE_FACTOR_ZERO; + + if ( (pos.attacks_from(weakerBishopSq) & ray) + && square_distance(weakerBishopSq, pawnSq) >= 3) + return SCALE_FACTOR_ZERO; + } } return SCALE_FACTOR_NONE; } -/// KBPKNScalingFunction scales KBP vs KN endgames. There is a single rule: +/// KBPPKBScalingFunction scales KBPP vs KB endgames. It detects a few basic +/// draws with opposite-colored bishops. +template<> +ScaleFactor ScalingFunction::apply(const Position& pos) const { + + 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 (same_color_squares(wbsq, 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) + && !same_color_squares(ksq, wbsq)) + return SCALE_FACTOR_ZERO; + 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 + && !same_color_squares(ksq, wbsq) + && ( bbsq == blockSq2 + || (pos.attacks_from(blockSq2) & pos.pieces(BISHOP, weakerSide)) + || rank_distance(r1, r2) >= 2)) + return SCALE_FACTOR_ZERO; + + else if ( ksq == blockSq2 + && !same_color_squares(ksq, wbsq) + && ( bbsq == blockSq1 + || (pos.attacks_from(blockSq1) & pos.pieces(BISHOP, weakerSide)))) + return SCALE_FACTOR_ZERO; + else + return SCALE_FACTOR_NONE; + + default: + // The pawns are not on the same file or adjacent files. No scaling. + 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. +template<> +ScaleFactor ScalingFunction::apply(const Position& pos) const { -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 +805,22 @@ 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) + && ( !same_color_squares(weakerKingSq, strongerBishopSq) + || relative_rank(strongerSide, weakerKingSq) <= RANK_6)) + return SCALE_FACTOR_ZERO; 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) const { -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 +830,27 @@ 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 SCALE_FACTOR_ZERO; - 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 SCALE_FACTOR_ZERO; 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) 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); @@ -872,58 +859,51 @@ 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; - else - return ScaleFactor(0); -} - - -/// 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. - -void init_bitbases() { - generate_kpk_bitbase(KPKBitbase); + return probe_kpk(wksq, wpsq, bksq, stm) ? SCALE_FACTOR_NONE : SCALE_FACTOR_ZERO; } namespace { - // Probe the KP vs K bitbase: + // 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)); - } + int wp = square_file(wpsq) + 4 * (square_rank(wpsq) - 1); + int index = int(stm) + 2 * bksq + 128 * wksq + 8192 * wp; + assert(index >= 0 && index < 24576 * 8); + + return KPKBitbase[index / 8] & (1 << (index & 7)); + } }