X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fendgame.cpp;h=913be63f1702c21eb4d76277c2cc4a6daaeb3954;hp=882c07cbf43d7c9ec3d08218920408c3509f7e07;hb=94b9c65e09b5d396bebb29b62d9979139b5fbdfa;hpb=9f28d8a854d05c6c6edcd6f8911b352477f82c91 diff --git a/src/endgame.cpp b/src/endgame.cpp index 882c07cb..913be63f 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) 2008-2009 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 @@ -65,13 +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]); @@ -99,15 +99,24 @@ namespace { //// Functions //// +/// 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); +} + + /// 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 EvaluationFunction::apply(const Position& pos) { +Value EvaluationFunction::apply(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(weakerSide) == VALUE_ZERO); + assert(pos.piece_count(weakerSide, PAWN) == VALUE_ZERO); Square winnerKSq = pos.king_square(strongerSide); Square loserKSq = pos.king_square(weakerSide); @@ -117,23 +126,23 @@ Value EvaluationFunction::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. template<> -Value EvaluationFunction::apply(const Position& pos) { +Value EvaluationFunction::apply(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(weakerSide) == VALUE_ZERO); + assert(pos.piece_count(weakerSide, PAWN) == VALUE_ZERO); assert(pos.non_pawn_material(strongerSide) == KnightValueMidgame + BishopValueMidgame); assert(pos.piece_count(strongerSide, BISHOP) == 1); assert(pos.piece_count(strongerSide, KNIGHT) == 1); @@ -143,7 +152,10 @@ Value EvaluationFunction::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); @@ -153,16 +165,16 @@ Value EvaluationFunction::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. template<> -Value EvaluationFunction::apply(const Position& pos) { +Value EvaluationFunction::apply(const Position& pos) const { - assert(pos.non_pawn_material(strongerSide) == Value(0)); - assert(pos.non_pawn_material(weakerSide) == Value(0)); + assert(pos.non_pawn_material(strongerSide) == VALUE_ZERO); + assert(pos.non_pawn_material(weakerSide) == VALUE_ZERO); assert(pos.piece_count(strongerSide, PAWN) == 1); assert(pos.piece_count(weakerSide, PAWN) == 0); @@ -186,9 +198,9 @@ Value EvaluationFunction::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)) @@ -198,7 +210,7 @@ Value EvaluationFunction::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; } @@ -207,7 +219,7 @@ Value EvaluationFunction::apply(const Position& pos) { /// far advanced with support of the king, while the attacking king is far /// away. template<> -Value EvaluationFunction::apply(const Position& pos) { +Value EvaluationFunction::apply(const Position& pos) const { assert(pos.non_pawn_material(strongerSide) == RookValueMidgame); assert(pos.piece_count(strongerSide, PAWN) == 0); @@ -239,7 +251,7 @@ Value EvaluationFunction::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)); @@ -257,14 +269,14 @@ Value EvaluationFunction::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. template<> -Value EvaluationFunction::apply(const Position& pos) { +Value EvaluationFunction::apply(const Position& pos) const { assert(pos.non_pawn_material(strongerSide) == RookValueMidgame); assert(pos.piece_count(strongerSide, PAWN) == 0); @@ -273,14 +285,14 @@ Value EvaluationFunction::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. template<> -Value EvaluationFunction::apply(const Position& pos) { +Value EvaluationFunction::apply(const Position& pos) const { assert(pos.non_pawn_material(strongerSide) == RookValueMidgame); assert(pos.piece_count(strongerSide, PAWN) == 0); @@ -291,10 +303,12 @@ Value EvaluationFunction::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; } @@ -304,7 +318,7 @@ Value EvaluationFunction::apply(const Position& pos) { /// for the defending side in the search, this is usually sufficient to be /// able to win KQ vs KR. template<> -Value EvaluationFunction::apply(const Position& pos) { +Value EvaluationFunction::apply(const Position& pos) const { assert(pos.non_pawn_material(strongerSide) == QueenValueMidgame); assert(pos.piece_count(strongerSide, PAWN) == 0); @@ -319,11 +333,11 @@ Value EvaluationFunction::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; } template<> -Value EvaluationFunction::apply(const Position& pos) { +Value EvaluationFunction::apply(const Position& pos) const { assert(pos.piece_count(strongerSide, BISHOP) == 2); assert(pos.non_pawn_material(strongerSide) == 2*BishopValueMidgame); @@ -343,31 +357,31 @@ Value EvaluationFunction::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; } /// 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&) { - return Value(0); +Value EvaluationFunction::apply(const Position&) const { + return VALUE_ZERO; } template<> -Value EvaluationFunction::apply(const Position&) { - return Value(0); +Value EvaluationFunction::apply(const Position&) const { + return VALUE_ZERO; } /// 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. template<> -ScaleFactor ScalingFunction::apply(const Position& pos) { +ScaleFactor ScalingFunction::apply(const Position& pos) const { assert(pos.non_pawn_material(strongerSide) == BishopValueMidgame); assert(pos.piece_count(strongerSide, BISHOP) == 1); @@ -387,7 +401,7 @@ ScaleFactor ScalingFunction::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 @@ -401,15 +415,15 @@ ScaleFactor ScalingFunction::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; @@ -421,7 +435,7 @@ ScaleFactor ScalingFunction::apply(const Position& pos) { /// It tests for fortress draws with a rook on the third rank defended by /// a pawn. template<> -ScaleFactor ScalingFunction::apply(const Position& pos) { +ScaleFactor ScalingFunction::apply(const Position& pos) const { assert(pos.non_pawn_material(strongerSide) == QueenValueMidgame); assert(pos.piece_count(strongerSide, QUEEN) == 1); @@ -434,11 +448,11 @@ ScaleFactor ScalingFunction::apply(const Position& pos) { && relative_rank(weakerSide, pos.king_square(strongerSide)) >= RANK_4 && (pos.pieces(ROOK, weakerSide) & relative_rank_bb(weakerSide, RANK_3)) && (pos.pieces(PAWN, weakerSide) & relative_rank_bb(weakerSide, RANK_2)) - && (pos.piece_attacks(kingSq) & pos.pieces(PAWN, weakerSide))) + && (pos.attacks_from(kingSq) & pos.pieces(PAWN, weakerSide))) { Square rsq = pos.piece_list(weakerSide, ROOK, 0); - if (pos.pawn_attacks(strongerSide, rsq) & pos.pieces(PAWN, weakerSide)) - return ScaleFactor(0); + if (pos.attacks_from(rsq, strongerSide) & pos.pieces(PAWN, weakerSide)) + return SCALE_FACTOR_ZERO; } return SCALE_FACTOR_NONE; } @@ -452,7 +466,7 @@ ScaleFactor ScalingFunction::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 ScalingFunction::apply(const Position& pos) const { assert(pos.non_pawn_material(strongerSide) == RookValueMidgame); assert(pos.piece_count(strongerSide, PAWN) == 1); @@ -495,7 +509,7 @@ ScaleFactor ScalingFunction::apply(const Position &pos) { && square_distance(bksq, queeningSq) <= 1 && wksq <= SQ_H5 && (square_rank(brsq) == RANK_6 || (r <= RANK_3 && square_rank(wrsq) != RANK_6))) - return ScaleFactor(0); + 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. @@ -503,13 +517,13 @@ ScaleFactor ScalingFunction::apply(const Position &pos) { && 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); + return SCALE_FACTOR_ZERO; if ( r >= RANK_6 && bksq == queeningSq && square_rank(brsq) == RANK_1 && (!tempo || square_distance(wksq, wpsq) >= 2)) - return ScaleFactor(0); + 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. @@ -518,7 +532,7 @@ ScaleFactor ScalingFunction::apply(const Position &pos) { && (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); + return SCALE_FACTOR_ZERO; // If the defending king blocks the pawn and the attacking king is too far // away, it's a draw. @@ -526,7 +540,7 @@ ScaleFactor ScalingFunction::apply(const Position &pos) { && bksq == wpsq + DELTA_N && square_distance(wksq, wpsq) - tempo >= 2 && square_distance(wksq, brsq) - tempo >= 2) - return ScaleFactor(0); + 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, @@ -549,8 +563,8 @@ ScaleFactor ScalingFunction::apply(const Position &pos) { || ( 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))); + - 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. @@ -570,7 +584,7 @@ ScaleFactor ScalingFunction::apply(const Position &pos) { /// 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 ScalingFunction::apply(const Position& pos) const { assert(pos.non_pawn_material(strongerSide) == RookValueMidgame); assert(pos.piece_count(strongerSide, PAWN) == 2); @@ -609,43 +623,35 @@ ScaleFactor ScalingFunction::apply(const Position &pos) { /// 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 ScalingFunction::apply(const Position& pos) const { - assert(pos.non_pawn_material(strongerSide) == Value(0)); + assert(pos.non_pawn_material(strongerSide) == VALUE_ZERO); assert(pos.piece_count(strongerSide, PAWN) >= 2); - assert(pos.non_pawn_material(weakerSide) == Value(0)); + assert(pos.non_pawn_material(weakerSide) == VALUE_ZERO); assert(pos.piece_count(weakerSide, PAWN) == 0); + 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 ( 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) { // 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; } @@ -655,7 +661,7 @@ ScaleFactor ScalingFunction::apply(const Position &pos) { /// 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 ScalingFunction::apply(const Position& pos) const { assert(pos.non_pawn_material(strongerSide) == BishopValueMidgame); assert(pos.piece_count(strongerSide, BISHOP) == 1); @@ -672,12 +678,12 @@ ScaleFactor ScalingFunction::apply(const Position &pos) { // 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) + && ( !same_color_squares(weakerKingSq, strongerBishopSq) || relative_rank(strongerSide, weakerKingSq) <= RANK_6)) - return ScaleFactor(0); + return SCALE_FACTOR_ZERO; // Case 2: Opposite colored bishops - if (square_color(strongerBishopSq) != square_color(weakerBishopSq)) + if (!same_color_squares(strongerBishopSq, weakerBishopSq)) { // We assume that the position is drawn in the following three situations: // @@ -690,15 +696,16 @@ ScaleFactor ScalingFunction::apply(const Position &pos) { // reasonably well. if (relative_rank(strongerSide, pawnSq) <= RANK_5) - return ScaleFactor(0); + 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 ScaleFactor(0); - if( (pos.piece_attacks(weakerBishopSq) & ray) - && square_distance(weakerBishopSq, pawnSq) >= 3) - return ScaleFactor(0); + return SCALE_FACTOR_ZERO; + + if ( (pos.attacks_from(weakerBishopSq) & ray) + && square_distance(weakerBishopSq, pawnSq) >= 3) + return SCALE_FACTOR_ZERO; } } return SCALE_FACTOR_NONE; @@ -708,7 +715,7 @@ ScaleFactor ScalingFunction::apply(const Position &pos) { /// KBPPKBScalingFunction scales KBPP vs KB endgames. It detects a few basic /// draws with opposite-colored bishops. template<> -ScaleFactor ScalingFunction::apply(const Position& pos) { +ScaleFactor ScalingFunction::apply(const Position& pos) const { assert(pos.non_pawn_material(strongerSide) == BishopValueMidgame); assert(pos.piece_count(strongerSide, BISHOP) == 1); @@ -720,7 +727,7 @@ ScaleFactor ScalingFunction::apply(const Position& pos) { Square wbsq = pos.piece_list(strongerSide, BISHOP, 0); Square bbsq = pos.piece_list(weakerSide, BISHOP, 0); - if (square_color(wbsq) == square_color(bbsq)) + if (same_color_squares(wbsq, bbsq)) // Not opposite-colored bishops, no scaling return SCALE_FACTOR_NONE; @@ -749,8 +756,8 @@ ScaleFactor ScalingFunction::apply(const Position& pos) { // 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); + && !same_color_squares(ksq, wbsq)) + return SCALE_FACTOR_ZERO; else return SCALE_FACTOR_NONE; @@ -759,16 +766,17 @@ ScaleFactor ScalingFunction::apply(const Position& pos) { // 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) + && !same_color_squares(ksq, wbsq) && ( bbsq == blockSq2 - || (pos.piece_attacks(blockSq2) & pos.pieces(BISHOP, weakerSide)) + || (pos.attacks_from(blockSq2) & pos.pieces(BISHOP, weakerSide)) || rank_distance(r1, r2) >= 2)) - return ScaleFactor(0); + return SCALE_FACTOR_ZERO; + else if ( ksq == blockSq2 - && square_color(ksq) != square_color(wbsq) + && !same_color_squares(ksq, wbsq) && ( bbsq == blockSq1 - || (pos.piece_attacks(blockSq1) & pos.pieces(BISHOP, weakerSide)))) - return ScaleFactor(0); + || (pos.attacks_from(blockSq1) & pos.pieces(BISHOP, weakerSide)))) + return SCALE_FACTOR_ZERO; else return SCALE_FACTOR_NONE; @@ -784,7 +792,7 @@ ScaleFactor ScalingFunction::apply(const Position& pos) { /// 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 ScalingFunction::apply(const Position& pos) const { assert(pos.non_pawn_material(strongerSide) == BishopValueMidgame); assert(pos.piece_count(strongerSide, BISHOP) == 1); @@ -799,9 +807,9 @@ ScaleFactor ScalingFunction::apply(const Position &pos) { if ( square_file(weakerKingSq) == square_file(pawnSq) && relative_rank(strongerSide, pawnSq) < relative_rank(strongerSide, weakerKingSq) - && ( square_color(weakerKingSq) != square_color(strongerBishopSq) + && ( !same_color_squares(weakerKingSq, strongerBishopSq) || relative_rank(strongerSide, weakerKingSq) <= RANK_6)) - return ScaleFactor(0); + return SCALE_FACTOR_ZERO; return SCALE_FACTOR_NONE; } @@ -811,12 +819,12 @@ ScaleFactor ScalingFunction::apply(const Position &pos) { /// 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 ScalingFunction::apply(const Position& pos) const { 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.non_pawn_material(weakerSide) == VALUE_ZERO); assert(pos.piece_count(weakerSide, PAWN) == 0); Square pawnSq = pos.piece_list(strongerSide, PAWN, 0); @@ -824,11 +832,11 @@ ScaleFactor ScalingFunction::apply(const Position &pos) { if ( pawnSq == relative_square(strongerSide, SQ_A7) && square_distance(weakerKingSq, relative_square(strongerSide, SQ_A8)) <= 1) - return ScaleFactor(0); + return SCALE_FACTOR_ZERO; if ( pawnSq == relative_square(strongerSide, SQ_H7) && square_distance(weakerKingSq, relative_square(strongerSide, SQ_H8)) <= 1) - return ScaleFactor(0); + return SCALE_FACTOR_ZERO; return SCALE_FACTOR_NONE; } @@ -841,10 +849,10 @@ ScaleFactor ScalingFunction::apply(const Position &pos) { /// 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 ScalingFunction::apply(const Position& pos) const { - assert(pos.non_pawn_material(strongerSide) == Value(0)); - assert(pos.non_pawn_material(weakerSide) == Value(0)); + assert(pos.non_pawn_material(strongerSide) == VALUE_ZERO); + assert(pos.non_pawn_material(weakerSide) == VALUE_ZERO); assert(pos.piece_count(WHITE, PAWN) == 1); assert(pos.piece_count(BLACK, PAWN) == 1); @@ -881,32 +889,21 @@ ScaleFactor ScalingFunction::apply(const Position &pos) { // 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; + 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); - assert(index >= 0 && index < 24576*8); - return KPKBitbase[index/8] & (1 << (index&7)); + return KPKBitbase[index / 8] & (1 << (index & 7)); } }