X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fendgame.cpp;h=daef61f2f587ecb6ba858b1a985a9ae113c3415c;hp=b9ac17a2e9cf6486c4ca8ae22600bf46845d8753;hb=3054db989d28bee4c491811ba81a7933eb37ba14;hpb=0c68971c13f02dc0303716457fe96ed2f8c095e5 diff --git a/src/endgame.cpp b/src/endgame.cpp index b9ac17a2..daef61f2 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) 2008-2013 Marco Costalba, Joona Kiiski, Tord Romstad + Copyright (C) 2008-2015 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 @@ -60,15 +60,29 @@ namespace { const int PushAway [8] = { 0, 5, 20, 40, 60, 80, 90, 100 }; #ifndef NDEBUG - bool verify_material(const Position& pos, Color c, Value npm, int num_pawns) { - return pos.non_pawn_material(c) == npm && pos.count(c) == num_pawns; + bool verify_material(const Position& pos, Color c, Value npm, int pawnsCnt) { + return pos.non_pawn_material(c) == npm && pos.count(c) == pawnsCnt; } #endif - // Get the material key of a Position out of the given endgame key code - // like "KBPKN". The trick here is to first forge an ad-hoc fen string - // and then let a Position object to do the work for us. Note that the - // fen string could correspond to an illegal position. + // Map the square as if strongSide is white and strongSide's only pawn + // is on the left half of the board. + Square normalize(const Position& pos, Color strongSide, Square sq) { + + assert(pos.count(strongSide) == 1); + + if (file_of(pos.list(strongSide)[0]) >= FILE_E) + sq = Square(sq ^ 7); // Mirror SQ_H1 -> SQ_A1 + + if (strongSide == BLACK) + sq = ~sq; + + return sq; + } + + // Get the material key of Position out of the given endgame key code + // like "KBPKN". The trick here is to first forge an ad-hoc FEN string + // and then let a Position object do the work for us. Key key(const string& code, Color c) { assert(code.length() > 0 && code.length() < 8); @@ -79,15 +93,12 @@ namespace { std::transform(sides[c].begin(), sides[c].end(), sides[c].begin(), tolower); - string fen = sides[0] + char('0' + int(8 - code.length())) - + sides[1] + "/8/8/8/8/8/8/8 w - - 0 10"; + string fen = sides[0] + char(8 - sides[0].length() + '0') + "/8/8/8/8/8/8/" + + sides[1] + char(8 - sides[1].length() + '0') + " w - - 0 10"; - return Position(fen, false, NULL).material_key(); + return Position(fen, false, nullptr).material_key(); } - template - void delete_endgame(const typename M::value_type& p) { delete p.second; } - } // namespace @@ -103,7 +114,6 @@ Endgames::Endgames() { add("KRKN"); add("KQKP"); add("KQKR"); - add("KBBKN"); add("KNPK"); add("KNPKB"); @@ -115,22 +125,16 @@ Endgames::Endgames() { add("KRPPKRP"); } -Endgames::~Endgames() { - for_each(m1.begin(), m1.end(), delete_endgame); - for_each(m2.begin(), m2.end(), delete_endgame); -} - -template +template void Endgames::add(const string& code) { - - map((Endgame*)0)[key(code, WHITE)] = new Endgame(WHITE); - map((Endgame*)0)[key(code, BLACK)] = new Endgame(BLACK); + map()[key(code, WHITE)] = std::unique_ptr>(new Endgame(WHITE)); + map()[key(code, BLACK)] = std::unique_ptr>(new Endgame(BLACK)); } /// 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 +/// 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<> @@ -149,11 +153,13 @@ Value Endgame::operator()(const Position& pos) const { Value result = pos.non_pawn_material(strongSide) + pos.count(strongSide) * PawnValueEg + PushToEdges[loserKSq] - + PushClose[square_distance(winnerKSq, loserKSq)]; + + PushClose[distance(winnerKSq, loserKSq)]; if ( pos.count(strongSide) || pos.count(strongSide) - || pos.bishop_pair(strongSide)) + ||(pos.count(strongSide) && pos.count(strongSide)) + ||(pos.count(strongSide) > 1 && opposite_colors(pos.list(strongSide)[0], + pos.list(strongSide)[1]))) result += VALUE_KNOWN_WIN; return strongSide == pos.side_to_move() ? result : -result; @@ -172,17 +178,17 @@ Value Endgame::operator()(const Position& pos) const { Square loserKSq = pos.king_square(weakSide); Square bishopSq = pos.list(strongSide)[0]; - // 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. + // kbnk_mate_table() tries to drive toward corners A1 or H8. If we have a + // bishop that cannot reach the above squares, we flip the kings in order + // to drive the enemy toward corners A8 or H1. if (opposite_colors(bishopSq, SQ_A1)) { - winnerKSq = mirror(winnerKSq); - loserKSq = mirror(loserKSq); + winnerKSq = ~winnerKSq; + loserKSq = ~loserKSq; } Value result = VALUE_KNOWN_WIN - + PushClose[square_distance(winnerKSq, loserKSq)] + + PushClose[distance(winnerKSq, loserKSq)] + PushToCorners[loserKSq]; return strongSide == pos.side_to_move() ? result : -result; @@ -196,27 +202,14 @@ Value Endgame::operator()(const Position& pos) const { assert(verify_material(pos, strongSide, VALUE_ZERO, 1)); assert(verify_material(pos, weakSide, VALUE_ZERO, 0)); - Square wksq = pos.king_square(strongSide); - Square bksq = pos.king_square(weakSide); - Square psq = pos.list(strongSide)[0]; - Color us = pos.side_to_move(); + // Assume strongSide is white and the pawn is on files A-D + Square wksq = normalize(pos, strongSide, pos.king_square(strongSide)); + Square bksq = normalize(pos, strongSide, pos.king_square(weakSide)); + Square psq = normalize(pos, strongSide, pos.list(strongSide)[0]); - if (strongSide == BLACK) - { - wksq = ~wksq; - bksq = ~bksq; - psq = ~psq; - us = ~us; - } - - if (file_of(psq) >= FILE_E) - { - wksq = mirror(wksq); - bksq = mirror(bksq); - psq = mirror(psq); - } + Color us = strongSide == pos.side_to_move() ? WHITE : BLACK; - if (!Bitbases::probe_kpk(wksq, psq, bksq, us)) + if (!Bitbases::probe(wksq, psq, bksq, us)) return VALUE_DRAW; Value result = VALUE_KNOWN_WIN + PawnValueEg + Value(rank_of(psq)); @@ -235,45 +228,36 @@ Value Endgame::operator()(const Position& pos) const { assert(verify_material(pos, strongSide, RookValueMg, 0)); assert(verify_material(pos, weakSide, VALUE_ZERO, 1)); - Square wksq = pos.king_square(strongSide); - Square bksq = pos.king_square(weakSide); - Square rsq = pos.list(strongSide)[0]; - Square psq = pos.list(weakSide)[0]; - - if (strongSide == BLACK) - { - wksq = ~wksq; - bksq = ~bksq; - rsq = ~rsq; - psq = ~psq; - } + Square wksq = relative_square(strongSide, pos.king_square(strongSide)); + Square bksq = relative_square(strongSide, pos.king_square(weakSide)); + Square rsq = relative_square(strongSide, pos.list(strongSide)[0]); + Square psq = relative_square(strongSide, pos.list(weakSide)[0]); - Square queeningSq = file_of(psq) | RANK_1; + Square queeningSq = make_square(file_of(psq), RANK_1); Value result; // If the stronger side's king is in front of the pawn, it's a win if (wksq < psq && file_of(wksq) == file_of(psq)) - result = RookValueEg - Value(square_distance(wksq, psq)); + result = RookValueEg - distance(wksq, psq); // If the weaker side's king is too far from the pawn and the rook, // it's a win. - else if ( square_distance(bksq, psq) >= 3 + (pos.side_to_move() == weakSide) - && square_distance(bksq, rsq) >= 3) - result = RookValueEg - Value(square_distance(wksq, psq)); + else if ( distance(bksq, psq) >= 3 + (pos.side_to_move() == weakSide) + && distance(bksq, rsq) >= 3) + result = RookValueEg - distance(wksq, psq); // If the pawn is far advanced and supported by the defending king, // the position is drawish else if ( rank_of(bksq) <= RANK_3 - && square_distance(bksq, psq) == 1 + && distance(bksq, psq) == 1 && rank_of(wksq) >= RANK_4 - && square_distance(wksq, psq) > 2 + (pos.side_to_move() == strongSide)) - result = Value(80 - square_distance(wksq, psq) * 8); + && distance(wksq, psq) > 2 + (pos.side_to_move() == strongSide)) + result = Value(80) - 8 * distance(wksq, psq); else - result = Value(200) - - Value(square_distance(wksq, psq + DELTA_S) * 8) - + Value(square_distance(bksq, psq + DELTA_S) * 8) - + Value(square_distance(psq, queeningSq) * 8); + result = Value(200) - 8 * ( distance(wksq, psq + DELTA_S) + - distance(bksq, psq + DELTA_S) + - distance(psq, queeningSq)); return strongSide == pos.side_to_move() ? result : -result; } @@ -292,7 +276,7 @@ Value Endgame::operator()(const Position& pos) const { } -/// KR vs KN. The attacking side has slightly better winning chances than +/// KR vs KN. The attacking side has slightly better winning chances than /// in KR vs KB, particularly if the king and the knight are far apart. template<> Value Endgame::operator()(const Position& pos) const { @@ -302,14 +286,15 @@ Value Endgame::operator()(const Position& pos) const { Square bksq = pos.king_square(weakSide); Square bnsq = pos.list(weakSide)[0]; - Value result = Value(PushToEdges[bksq] + PushAway[square_distance(bksq, bnsq)]); + Value result = Value(PushToEdges[bksq] + PushAway[distance(bksq, bnsq)]); return strongSide == pos.side_to_move() ? result : -result; } -/// KQ vs KP. In general, a win for the stronger side, however, there are a few -/// important exceptions. Pawn on 7th rank, A,C,F or H file, with king next can -/// be a draw, so we scale down to distance between kings only. +/// KQ vs KP. In general, this is a win for the stronger side, but there are a +/// few important exceptions. A pawn on 7th rank and on the A,C,F or H files +/// with a king positioned next to it can be a draw, so in that case, we only +/// use the distance between the kings. template<> Value Endgame::operator()(const Position& pos) const { @@ -320,10 +305,10 @@ Value Endgame::operator()(const Position& pos) const { Square loserKSq = pos.king_square(weakSide); Square pawnSq = pos.list(weakSide)[0]; - Value result = Value(PushClose[square_distance(winnerKSq, loserKSq)]); + Value result = Value(PushClose[distance(winnerKSq, loserKSq)]); if ( relative_rank(weakSide, pawnSq) != RANK_7 - || square_distance(loserKSq, pawnSq) != 1 + || distance(loserKSq, pawnSq) != 1 || !((FileABB | FileCBB | FileFBB | FileHBB) & pawnSq)) result += QueenValueEg - PawnValueEg; @@ -333,9 +318,8 @@ Value Endgame::operator()(const Position& pos) const { /// KQ vs KR. This is almost identical to KX vs K: We give the attacking /// king a bonus for having the kings close together, and for forcing the -/// defending king towards the edge. If we also take care to avoid null move -/// for the defending side in the search, this is usually sufficient to be -/// able to win KQ vs KR. +/// defending king towards the edge. If we also take care to avoid null move for +/// the defending side in the search, this is usually sufficient to win KQ vs KR. template<> Value Endgame::operator()(const Position& pos) const { @@ -348,30 +332,7 @@ Value Endgame::operator()(const Position& pos) const { Value result = QueenValueEg - RookValueEg + PushToEdges[loserKSq] - + PushClose[square_distance(winnerKSq, loserKSq)]; - - return strongSide == pos.side_to_move() ? result : -result; -} - - -/// KBB vs KN. This is almost always a win. We try to push enemy king to a corner -/// and away from his knight. For a reference of this difficult endgame see: -/// en.wikipedia.org/wiki/Chess_endgame#Effect_of_tablebases_on_endgame_theory - -template<> -Value Endgame::operator()(const Position& pos) const { - - assert(verify_material(pos, strongSide, 2 * BishopValueMg, 0)); - assert(verify_material(pos, weakSide, KnightValueMg, 0)); - - Square winnerKSq = pos.king_square(strongSide); - Square loserKSq = pos.king_square(weakSide); - Square knightSq = pos.list(weakSide)[0]; - - Value result = VALUE_KNOWN_WIN - + PushToCorners[loserKSq] - + PushClose[square_distance(winnerKSq, loserKSq)] - + PushAway[square_distance(loserKSq, knightSq)]; + + PushClose[distance(winnerKSq, loserKSq)]; return strongSide == pos.side_to_move() ? result : -result; } @@ -379,10 +340,9 @@ Value Endgame::operator()(const Position& pos) const { /// Some cases of trivial draws template<> Value Endgame::operator()(const Position&) const { return VALUE_DRAW; } -template<> Value Endgame::operator()(const Position&) const { return VALUE_DRAW; } -/// K, bishop and one or more pawns vs K. It checks for draws with rook pawns and +/// KB and one or more pawns vs K. It checks for draws with rook pawns and /// a bishop of the wrong color. If such a draw is detected, SCALE_FACTOR_DRAW /// is returned. If not, the return value is SCALE_FACTOR_NONE, i.e. no scaling /// will be used. @@ -403,37 +363,37 @@ ScaleFactor Endgame::operator()(const Position& pos) const { && !(pawns & ~file_bb(pawnFile))) { Square bishopSq = pos.list(strongSide)[0]; - Square queeningSq = relative_square(strongSide, pawnFile | RANK_8); + Square queeningSq = relative_square(strongSide, make_square(pawnFile, RANK_8)); Square kingSq = pos.king_square(weakSide); if ( opposite_colors(queeningSq, bishopSq) - && square_distance(queeningSq, kingSq) <= 1) + && distance(queeningSq, kingSq) <= 1) return SCALE_FACTOR_DRAW; } - // All pawns on same B or G file? Then potential draw + // If all the pawns are on the same B or G file, then it's potentially a draw if ( (pawnFile == FILE_B || pawnFile == FILE_G) && !(pos.pieces(PAWN) & ~file_bb(pawnFile)) && pos.non_pawn_material(weakSide) == 0 && pos.count(weakSide) >= 1) { - // Get weakSide pawn that is closest to home rank + // Get weakSide pawn that is closest to the home rank Square weakPawnSq = backmost_sq(weakSide, pos.pieces(weakSide, PAWN)); Square strongKingSq = pos.king_square(strongSide); Square weakKingSq = pos.king_square(weakSide); Square bishopSq = pos.list(strongSide)[0]; - // Potential for a draw if our pawn is blocked on the 7th rank + // There's potential for a draw if our pawn is blocked on the 7th rank, // the bishop cannot attack it or they only have one pawn left if ( relative_rank(strongSide, weakPawnSq) == RANK_7 && (pos.pieces(strongSide, PAWN) & (weakPawnSq + pawn_push(weakSide))) && (opposite_colors(bishopSq, weakPawnSq) || pos.count(strongSide) == 1)) { - int strongKingDist = square_distance(weakPawnSq, strongKingSq); - int weakKingDist = square_distance(weakPawnSq, weakKingSq); + int strongKingDist = distance(weakPawnSq, strongKingSq); + int weakKingDist = distance(weakPawnSq, weakKingSq); - // Draw if the weak king is on it's back two ranks, within 2 + // It's a draw if the weak king is on its back two ranks, within 2 // squares of the blocking pawn and the strong king is not // closer. (I think this rule only fails in practically // unreachable positions such as 5k1K/6p1/6P1/8/8/3B4/8/8 w @@ -450,8 +410,8 @@ ScaleFactor Endgame::operator()(const Position& pos) const { } -/// K and queen vs K, rook and one or more pawns. It tests for fortress draws with -/// a rook on the third rank defended by a pawn. +/// KQ vs KR and one or more pawns. It tests for fortress draws with a rook on +/// the third rank defended by a pawn. template<> ScaleFactor Endgame::operator()(const Position& pos) const { @@ -464,63 +424,44 @@ ScaleFactor Endgame::operator()(const Position& pos) const { if ( relative_rank(weakSide, kingSq) <= RANK_2 && relative_rank(weakSide, pos.king_square(strongSide)) >= RANK_4 - && (pos.pieces(weakSide, ROOK) & rank_bb(relative_rank(weakSide, RANK_3))) - && (pos.pieces(weakSide, PAWN) & rank_bb(relative_rank(weakSide, RANK_2))) - && (pos.attacks_from(kingSq) & pos.pieces(weakSide, PAWN)) - && (pos.attacks_from(rsq, strongSide) & pos.pieces(weakSide, PAWN))) + && relative_rank(weakSide, rsq) == RANK_3 + && ( pos.pieces(weakSide, PAWN) + & pos.attacks_from(kingSq) + & pos.attacks_from(rsq, strongSide))) return SCALE_FACTOR_DRAW; return SCALE_FACTOR_NONE; } -/// K, rook and one pawn vs K and a rook. This function knows a handful of the -/// most important classes of drawn positions, but is far from perfect. It would -/// probably be a good idea to add more knowledge in the future. +/// KRP vs KR. This function knows a handful of the most important classes of +/// drawn positions, but is far from perfect. It would probably be a good idea +/// to add more knowledge in the future. /// /// It would also be nice to rewrite the actual code for this function, -/// which is mostly copied from Glaurung 1.x, and not very pretty. +/// which is mostly copied from Glaurung 1.x, and isn't very pretty. template<> ScaleFactor Endgame::operator()(const Position& pos) const { assert(verify_material(pos, strongSide, RookValueMg, 1)); assert(verify_material(pos, weakSide, RookValueMg, 0)); - Square wksq = pos.king_square(strongSide); - Square bksq = pos.king_square(weakSide); - Square wrsq = pos.list(strongSide)[0]; - Square wpsq = pos.list(strongSide)[0]; - Square brsq = pos.list(weakSide)[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 (strongSide == BLACK) - { - wksq = ~wksq; - wrsq = ~wrsq; - wpsq = ~wpsq; - bksq = ~bksq; - brsq = ~brsq; - } - - if (file_of(wpsq) > FILE_D) - { - wksq = mirror(wksq); - wrsq = mirror(wrsq); - wpsq = mirror(wpsq); - bksq = mirror(bksq); - brsq = mirror(brsq); - } + // Assume strongSide is white and the pawn is on files A-D + Square wksq = normalize(pos, strongSide, pos.king_square(strongSide)); + Square bksq = normalize(pos, strongSide, pos.king_square(weakSide)); + Square wrsq = normalize(pos, strongSide, pos.list(strongSide)[0]); + Square wpsq = normalize(pos, strongSide, pos.list(strongSide)[0]); + Square brsq = normalize(pos, strongSide, pos.list(weakSide)[0]); File f = file_of(wpsq); Rank r = rank_of(wpsq); - Square queeningSq = f | RANK_8; + Square queeningSq = make_square(f, RANK_8); int tempo = (pos.side_to_move() == strongSide); // If the pawn is not too far advanced and the defending king defends the // queening square, use the third-rank defence. if ( r <= RANK_5 - && square_distance(bksq, queeningSq) <= 1 + && distance(bksq, queeningSq) <= 1 && wksq <= SQ_H5 && (rank_of(brsq) == RANK_6 || (r <= RANK_3 && rank_of(wrsq) != RANK_6))) return SCALE_FACTOR_DRAW; @@ -528,15 +469,15 @@ ScaleFactor Endgame::operator()(const Position& pos) const { // 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 + && distance(bksq, queeningSq) <= 1 && rank_of(wksq) + tempo <= RANK_6 - && (rank_of(brsq) == RANK_1 || (!tempo && abs(file_of(brsq) - f) >= 3))) + && (rank_of(brsq) == RANK_1 || (!tempo && distance(brsq, wpsq) >= 3))) return SCALE_FACTOR_DRAW; if ( r >= RANK_6 && bksq == queeningSq && rank_of(brsq) == RANK_1 - && (!tempo || square_distance(wksq, wpsq) >= 2)) + && (!tempo || distance(wksq, wpsq) >= 2)) return SCALE_FACTOR_DRAW; // White pawn on a7 and rook on a8 is a draw if black's king is on g7 or h7 @@ -552,8 +493,8 @@ ScaleFactor Endgame::operator()(const Position& pos) const { // 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) + && distance(wksq, wpsq) - tempo >= 2 + && distance(wksq, brsq) - tempo >= 2) return SCALE_FACTOR_DRAW; // Pawn on the 7th rank supported by the rook from behind usually wins if the @@ -563,32 +504,32 @@ ScaleFactor Endgame::operator()(const Position& pos) const { && f != FILE_A && file_of(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)); + && (distance(wksq, queeningSq) < distance(bksq, queeningSq) - 2 + tempo) + && (distance(wksq, queeningSq) < distance(bksq, wrsq) + tempo)) + return ScaleFactor(SCALE_FACTOR_MAX - 2 * distance(wksq, queeningSq)); // Similar to the above, but with the pawn further back if ( f != FILE_A && file_of(wrsq) == f && wrsq < wpsq - && (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)))) + && (distance(wksq, queeningSq) < distance(bksq, queeningSq) - 2 + tempo) + && (distance(wksq, wpsq + DELTA_N) < distance(bksq, wpsq + DELTA_N) - 2 + tempo) + && ( distance(bksq, wrsq) + tempo >= 3 + || ( distance(wksq, queeningSq) < distance(bksq, wrsq) + tempo + && (distance(wksq, wpsq + DELTA_N) < distance(bksq, wrsq) + tempo)))) return ScaleFactor( SCALE_FACTOR_MAX - - 8 * square_distance(wpsq, queeningSq) - - 2 * square_distance(wksq, queeningSq)); + - 8 * distance(wpsq, queeningSq) + - 2 * distance(wksq, queeningSq)); - // If the pawn is not far advanced, and the defending king is somewhere in + // If the pawn is not far advanced and the defending king is somewhere in // the pawn's path, it's probably a draw. if (r <= RANK_4 && bksq > wpsq) { if (file_of(bksq) == file_of(wpsq)) return ScaleFactor(10); - if ( abs(file_of(bksq) - file_of(wpsq)) == 1 - && square_distance(wksq, bksq) > 2) - return ScaleFactor(24 - 2 * square_distance(wksq, bksq)); + if ( distance(bksq, wpsq) == 1 + && distance(wksq, bksq) > 2) + return ScaleFactor(24 - 2 * distance(wksq, bksq)); } return SCALE_FACTOR_NONE; } @@ -615,7 +556,7 @@ ScaleFactor Endgame::operator()(const Position& pos) const { // corner but not trapped there. if (rk == RANK_5 && !opposite_colors(bsq, psq)) { - int d = square_distance(psq + 3 * push, ksq); + int d = distance(psq + 3 * push, ksq); if (d <= 2 && !(d == 0 && ksq == pos.king_square(strongSide) + 2 * push)) return ScaleFactor(24); @@ -628,18 +569,17 @@ ScaleFactor Endgame::operator()(const Position& pos) const { // pawn from a reasonable distance and the defending king is near // the corner if ( rk == RANK_6 - && square_distance(psq + 2 * push, ksq) <= 1 + && distance(psq + 2 * push, ksq) <= 1 && (PseudoAttacks[BISHOP][bsq] & (psq + push)) - && file_distance(bsq, psq) >= 2) + && distance(bsq, psq) >= 2) return ScaleFactor(8); } return SCALE_FACTOR_NONE; } -/// K, rook and two pawns vs K, rook and one pawn. There is only a single -/// pattern: If the stronger side has no passed pawns and the defending king -/// is actively placed, the position is drawish. +/// KRPP vs KRP. There is just a single rule: if the stronger side has no passed +/// pawns and the defending king is actively placed, the position is drawish. template<> ScaleFactor Endgame::operator()(const Position& pos) const { @@ -656,8 +596,8 @@ ScaleFactor Endgame::operator()(const Position& pos) const { Rank r = std::max(relative_rank(strongSide, wpsq1), relative_rank(strongSide, wpsq2)); - if ( file_distance(bksq, wpsq1) <= 1 - && file_distance(bksq, wpsq2) <= 1 + if ( distance(bksq, wpsq1) <= 1 + && distance(bksq, wpsq2) <= 1 && relative_rank(strongSide, bksq) > r) { switch (r) { @@ -684,33 +624,23 @@ ScaleFactor Endgame::operator()(const Position& pos) const { Square ksq = pos.king_square(weakSide); Bitboard pawns = pos.pieces(strongSide, PAWN); + Square psq = pos.list(strongSide)[0]; + + // If all pawns are ahead of the king, on a single rook file and + // the king is within one file of the pawns, it's a draw. + if ( !(pawns & ~in_front_bb(weakSide, rank_of(ksq))) + && !((pawns & ~FileABB) && (pawns & ~FileHBB)) + && distance(ksq, psq) <= 1) + return SCALE_FACTOR_DRAW; - // Are all pawns on the 'a' file? - if (!(pawns & ~FileABB)) - { - // Does the defending king block the pawns? - if ( square_distance(ksq, relative_square(strongSide, SQ_A8)) <= 1 - || ( file_of(ksq) == FILE_A - && !(in_front_bb(strongSide, rank_of(ksq)) & pawns))) - return SCALE_FACTOR_DRAW; - } - // Are all pawns on the 'h' file? - else if (!(pawns & ~FileHBB)) - { - // Does the defending king block the pawns? - if ( square_distance(ksq, relative_square(strongSide, SQ_H8)) <= 1 - || ( file_of(ksq) == FILE_H - && !(in_front_bb(strongSide, rank_of(ksq)) & pawns))) - return SCALE_FACTOR_DRAW; - } return SCALE_FACTOR_NONE; } -/// K, bishop and a pawn vs K and a bishop. There are two rules: If the defending -/// king is somewhere along the path of the pawn, and the square of the king is -/// not of the same color as the stronger side's bishop, it's a draw. If the two -/// bishops have opposite color, it's almost always a draw. +/// KBP vs KB. There are two rules: if the defending king is somewhere along the +/// path of the pawn, and the square of the king is not of the same color as the +/// stronger side's bishop, it's a draw. If the two bishops have opposite color, +/// it's almost always a draw. template<> ScaleFactor Endgame::operator()(const Position& pos) const { @@ -752,7 +682,7 @@ ScaleFactor Endgame::operator()(const Position& pos) const { return SCALE_FACTOR_DRAW; if ( (pos.attacks_from(weakBishopSq) & path) - && square_distance(weakBishopSq, pawnSq) >= 3) + && distance(weakBishopSq, pawnSq) >= 3) return SCALE_FACTOR_DRAW; } } @@ -760,8 +690,7 @@ ScaleFactor Endgame::operator()(const Position& pos) const { } -/// K, bishop and two pawns vs K and bishop. It detects a few basic draws with -/// opposite-colored bishops. +/// KBPP vs KB. It detects a few basic draws with opposite-colored bishops template<> ScaleFactor Endgame::operator()(const Position& pos) const { @@ -784,19 +713,19 @@ ScaleFactor Endgame::operator()(const Position& pos) const { if (relative_rank(strongSide, psq1) > relative_rank(strongSide, psq2)) { blockSq1 = psq1 + pawn_push(strongSide); - blockSq2 = file_of(psq2) | rank_of(psq1); + blockSq2 = make_square(file_of(psq2), rank_of(psq1)); } else { blockSq1 = psq2 + pawn_push(strongSide); - blockSq2 = file_of(psq1) | rank_of(psq2); + blockSq2 = make_square(file_of(psq1), rank_of(psq2)); } - switch (file_distance(psq1, psq2)) + switch (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. + // Both pawns are on the same file. It's an easy draw if the defender firmly + // controls some square in the frontmost pawn's path. if ( file_of(ksq) == file_of(blockSq1) && relative_rank(strongSide, ksq) >= relative_rank(strongSide, blockSq1) && opposite_colors(ksq, wbsq)) @@ -805,14 +734,14 @@ ScaleFactor Endgame::operator()(const Position& pos) const { return SCALE_FACTOR_NONE; case 1: - // Pawns on adjacent 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. + // Pawns on adjacent files. It's a draw if the defender firmly controls the + // square in front of the frontmost pawn's path, and the square diagonally + // behind this square on the file of the other pawn. if ( ksq == blockSq1 && opposite_colors(ksq, wbsq) && ( bbsq == blockSq2 || (pos.attacks_from(blockSq2) & pos.pieces(weakSide, BISHOP)) - || abs(r1 - r2) >= 2)) + || distance(r1, r2) >= 2)) return SCALE_FACTOR_DRAW; else if ( ksq == blockSq2 @@ -830,9 +759,9 @@ ScaleFactor Endgame::operator()(const Position& pos) const { } -/// K, bisop and a pawn vs K and knight. 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. +/// KBP vs KN. There is a single rule: If the defending king is somewhere along +/// the path of the pawn, and the square of the king is not of the same color as +/// the stronger side's bishop, it's a draw. template<> ScaleFactor Endgame::operator()(const Position& pos) const { @@ -853,32 +782,27 @@ ScaleFactor Endgame::operator()(const Position& pos) const { } -/// K, knight and a pawn vs K. There is a single rule: If the pawn is a rook pawn -/// on the 7th rank and the defending king prevents the pawn from advancing, the -/// position is drawn. +/// KNP vs K. There is a single rule: if the pawn is a rook pawn on the 7th rank +/// and the defending king prevents the pawn from advancing, the position is drawn. template<> ScaleFactor Endgame::operator()(const Position& pos) const { assert(verify_material(pos, strongSide, KnightValueMg, 1)); assert(verify_material(pos, weakSide, VALUE_ZERO, 0)); - Square pawnSq = pos.list(strongSide)[0]; - Square weakKingSq = pos.king_square(weakSide); - - if ( pawnSq == relative_square(strongSide, SQ_A7) - && square_distance(weakKingSq, relative_square(strongSide, SQ_A8)) <= 1) - return SCALE_FACTOR_DRAW; + // Assume strongSide is white and the pawn is on files A-D + Square pawnSq = normalize(pos, strongSide, pos.list(strongSide)[0]); + Square weakKingSq = normalize(pos, strongSide, pos.king_square(weakSide)); - if ( pawnSq == relative_square(strongSide, SQ_H7) - && square_distance(weakKingSq, relative_square(strongSide, SQ_H8)) <= 1) + if (pawnSq == SQ_A7 && distance(SQ_A8, weakKingSq) <= 1) return SCALE_FACTOR_DRAW; return SCALE_FACTOR_NONE; } -/// K, knight and a pawn vs K and bishop. If knight can block bishop from taking -/// pawn, it's a win. Otherwise, drawn. +/// KNP vs KB. If knight can block bishop from taking pawn, it's a win. +/// Otherwise the position is drawn. template<> ScaleFactor Endgame::operator()(const Position& pos) const { @@ -889,42 +813,29 @@ ScaleFactor Endgame::operator()(const Position& pos) const { // King needs to get close to promoting pawn to prevent knight from blocking. // Rules for this are very tricky, so just approximate. if (forward_bb(strongSide, pawnSq) & pos.attacks_from(bishopSq)) - return ScaleFactor(square_distance(weakKingSq, pawnSq)); + return ScaleFactor(distance(weakKingSq, pawnSq)); return SCALE_FACTOR_NONE; } -/// K and a pawn vs K and a pawn. This is done by removing the weakest side's -/// pawn and probing the KP vs K bitbase: If the weakest side has a draw without -/// the pawn, she probably has at least a draw with the pawn as well. The exception -/// is when the stronger side's pawn is far advanced and not on a rook file; in -/// this case it is often possible to win (e.g. 8/4k3/3p4/3P4/6K1/8/8/8 w - - 0 1). +/// KP vs KP. This is done by removing the weakest side's pawn and probing the +/// KP vs K bitbase: If the weakest side has a draw without the pawn, it probably +/// has at least a draw with the pawn as well. The exception is when the stronger +/// side's pawn is far advanced and not on a rook file; in this case it is often +/// possible to win (e.g. 8/4k3/3p4/3P4/6K1/8/8/8 w - - 0 1). template<> ScaleFactor Endgame::operator()(const Position& pos) const { assert(verify_material(pos, strongSide, VALUE_ZERO, 1)); assert(verify_material(pos, weakSide, VALUE_ZERO, 1)); - Square wksq = pos.king_square(strongSide); - Square bksq = pos.king_square(weakSide); - Square psq = pos.list(strongSide)[0]; - Color us = pos.side_to_move(); + // Assume strongSide is white and the pawn is on files A-D + Square wksq = normalize(pos, strongSide, pos.king_square(strongSide)); + Square bksq = normalize(pos, strongSide, pos.king_square(weakSide)); + Square psq = normalize(pos, strongSide, pos.list(strongSide)[0]); - if (strongSide == BLACK) - { - wksq = ~wksq; - bksq = ~bksq; - psq = ~psq; - us = ~us; - } - - if (file_of(psq) >= FILE_E) - { - wksq = mirror(wksq); - bksq = mirror(bksq); - psq = mirror(psq); - } + Color us = strongSide == pos.side_to_move() ? WHITE : BLACK; // 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. @@ -933,5 +844,5 @@ ScaleFactor Endgame::operator()(const Position& pos) const { // Probe the KPK bitbase with the weakest side's pawn removed. If it's a draw, // it's probably at least a draw even with the pawn. - return Bitbases::probe_kpk(wksq, psq, bksq, us) ? SCALE_FACTOR_NONE : SCALE_FACTOR_DRAW; + return Bitbases::probe(wksq, psq, bksq, us) ? SCALE_FACTOR_NONE : SCALE_FACTOR_DRAW; }