X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fendgame.cpp;h=05de131fb2b26deff9336ddc2137db701752d56e;hp=c8d222804008c5d78019439bf5a53da610642d5f;hb=bc3b148d5712ef9ea00e74d3ff5aea10a4d3cabe;hpb=d9be00342cb1719b1ec510a4284f198607ce25df diff --git a/src/endgame.cpp b/src/endgame.cpp index c8d22280..05de131f 100644 --- a/src/endgame.cpp +++ b/src/endgame.cpp @@ -1,7 +1,8 @@ /* 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 + Copyright (C) 2015-2018 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad Stockfish is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by @@ -21,7 +22,6 @@ #include #include "bitboard.h" -#include "bitcount.h" #include "endgame.h" #include "movegen.h" @@ -31,7 +31,7 @@ namespace { // Table used to drive the king towards the edge of the board // in KX vs K and KQ vs KR endgames. - const int PushToEdges[SQUARE_NB] = { + constexpr int PushToEdges[SQUARE_NB] = { 100, 90, 80, 70, 70, 80, 90, 100, 90, 70, 60, 50, 50, 60, 70, 90, 80, 60, 40, 30, 30, 40, 60, 80, @@ -39,12 +39,12 @@ namespace { 70, 50, 30, 20, 20, 30, 50, 70, 80, 60, 40, 30, 30, 40, 60, 80, 90, 70, 60, 50, 50, 60, 70, 90, - 100, 90, 80, 70, 70, 80, 90, 100, + 100, 90, 80, 70, 70, 80, 90, 100 }; // Table used to drive the king towards a corner square of the // right color in KBN vs K endgames. - const int PushToCorners[SQUARE_NB] = { + constexpr int PushToCorners[SQUARE_NB] = { 200, 190, 180, 170, 160, 150, 140, 130, 190, 180, 170, 160, 150, 140, 130, 140, 180, 170, 155, 140, 140, 125, 140, 150, @@ -56,81 +56,38 @@ namespace { }; // Tables used to drive a piece towards or away from another piece - const int PushClose[8] = { 0, 0, 100, 80, 60, 40, 20, 10 }; - const int PushAway [8] = { 0, 5, 20, 40, 60, 80, 90, 100 }; + constexpr int PushClose[8] = { 0, 0, 100, 80, 60, 40, 20, 10 }; + constexpr int PushAway [8] = { 0, 5, 20, 40, 60, 80, 90, 100 }; + + // Pawn Rank based scaling factors used in KRPPKRP endgame + constexpr int KRPPKRPScaleFactors[RANK_NB] = { 0, 9, 10, 14, 21, 44, 0, 0 }; #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. - Key key(const string& code, Color c) { - - assert(code.length() > 0 && code.length() < 8); - assert(code[0] == 'K'); + // 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) { - string sides[] = { code.substr(code.find('K', 1)), // Weak - code.substr(0, code.find('K', 1)) }; // Strong + assert(pos.count(strongSide) == 1); - std::transform(sides[c].begin(), sides[c].end(), sides[c].begin(), tolower); + if (file_of(pos.square(strongSide)) >= FILE_E) + sq = Square(sq ^ 7); // Mirror SQ_H1 -> SQ_A1 - string fen = sides[0] + char('0' + int(8 - code.length())) - + sides[1] + "/8/8/8/8/8/8/8 w - - 0 10"; + if (strongSide == BLACK) + sq = ~sq; - return Position(fen, false, NULL).material_key(); + return sq; } - template - void delete_endgame(const typename M::value_type& p) { delete p.second; } - } // namespace -/// Endgames members definitions - -Endgames::Endgames() { - - add("KPK"); - add("KNNK"); - add("KBNK"); - add("KRKP"); - add("KRKB"); - add("KRKN"); - add("KQKP"); - add("KQKR"); - add("KBBKN"); - - add("KNPK"); - add("KNPKB"); - add("KRPKR"); - add("KRPKB"); - add("KBPKB"); - add("KBPKN"); - add("KBPPKB"); - add("KRPPKRP"); -} - -Endgames::~Endgames() { - - for_each(m1.begin(), m1.end(), delete_endgame); - for_each(m2.begin(), m2.end(), delete_endgame); -} - -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); -} - - /// 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<> @@ -143,18 +100,20 @@ Value Endgame::operator()(const Position& pos) const { if (pos.side_to_move() == weakSide && !MoveList(pos).size()) return VALUE_DRAW; - Square winnerKSq = pos.king_square(strongSide); - Square loserKSq = pos.king_square(weakSide); + Square winnerKSq = pos.square(strongSide); + Square loserKSq = pos.square(weakSide); 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)) - result += VALUE_KNOWN_WIN; + ||(pos.count(strongSide) && pos.count(strongSide)) + || ( (pos.pieces(strongSide, BISHOP) & ~DarkSquares) + && (pos.pieces(strongSide, BISHOP) & DarkSquares))) + result = std::min(result + VALUE_KNOWN_WIN, VALUE_MATE_IN_MAX_PLY - 1); return strongSide == pos.side_to_move() ? result : -result; } @@ -168,21 +127,21 @@ Value Endgame::operator()(const Position& pos) const { assert(verify_material(pos, strongSide, KnightValueMg + BishopValueMg, 0)); assert(verify_material(pos, weakSide, VALUE_ZERO, 0)); - Square winnerKSq = pos.king_square(strongSide); - Square loserKSq = pos.king_square(weakSide); - Square bishopSq = pos.list(strongSide)[0]; + Square winnerKSq = pos.square(strongSide); + Square loserKSq = pos.square(weakSide); + Square bishopSq = pos.square(strongSide); - // 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 +155,14 @@ 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.square(strongSide)); + Square bksq = normalize(pos, strongSide, pos.square(weakSide)); + Square psq = normalize(pos, strongSide, pos.square(strongSide)); - 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)); @@ -235,51 +181,42 @@ 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]; + Square wksq = relative_square(strongSide, pos.square(strongSide)); + Square bksq = relative_square(strongSide, pos.square(weakSide)); + Square rsq = relative_square(strongSide, pos.square(strongSide)); + Square psq = relative_square(strongSide, pos.square(weakSide)); - if (strongSide == BLACK) - { - wksq = ~wksq; - bksq = ~bksq; - rsq = ~rsq; - psq = ~psq; - } - - 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)); + if (forward_file_bb(WHITE, wksq) & psq) + result = RookValueEg - distance(wksq, psq); // If the weaker side's king is too far from the pawn and the rook, // it's a win. - else if ( square_distance(bksq, 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 + SOUTH) + - distance(bksq, psq + SOUTH) + - distance(psq, queeningSq)); return strongSide == pos.side_to_move() ? result : -result; } -/// KR vs KB. This is very simple, and always returns drawish scores. The +/// KR vs KB. This is very simple, and always returns drawish scores. The /// score is slightly bigger when the defending king is close to the edge. template<> Value Endgame::operator()(const Position& pos) const { @@ -287,12 +224,12 @@ Value Endgame::operator()(const Position& pos) const { assert(verify_material(pos, strongSide, RookValueMg, 0)); assert(verify_material(pos, weakSide, BishopValueMg, 0)); - Value result = Value(PushToEdges[pos.king_square(weakSide)]); + Value result = Value(PushToEdges[pos.square(weakSide)]); return strongSide == pos.side_to_move() ? result : -result; } -/// KR vs KN. The attacking side has slightly better winning chances than +/// KR vs KN. The attacking side has slightly better winning chances than /// in KR vs KB, particularly if the king and the knight are far apart. template<> Value Endgame::operator()(const Position& pos) const { @@ -300,30 +237,31 @@ Value Endgame::operator()(const Position& pos) const { assert(verify_material(pos, strongSide, RookValueMg, 0)); assert(verify_material(pos, weakSide, KnightValueMg, 0)); - Square bksq = pos.king_square(weakSide); - Square bnsq = pos.list(weakSide)[0]; - Value result = Value(PushToEdges[bksq] + PushAway[square_distance(bksq, bnsq)]); + Square bksq = pos.square(weakSide); + Square bnsq = pos.square(weakSide); + Value result = Value(PushToEdges[bksq] + PushAway[distance(bksq, bnsq)]); return strongSide == pos.side_to_move() ? result : -result; } -/// 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 { assert(verify_material(pos, strongSide, QueenValueMg, 0)); assert(verify_material(pos, weakSide, VALUE_ZERO, 1)); - Square winnerKSq = pos.king_square(strongSide); - Square loserKSq = pos.king_square(weakSide); - Square pawnSq = pos.list(weakSide)[0]; + Square winnerKSq = pos.square(strongSide); + Square loserKSq = pos.square(weakSide); + Square pawnSq = pos.square(weakSide); - 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; @@ -333,45 +271,21 @@ 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 { assert(verify_material(pos, strongSide, QueenValueMg, 0)); assert(verify_material(pos, weakSide, RookValueMg, 0)); - Square winnerKSq = pos.king_square(strongSide); - Square loserKSq = pos.king_square(weakSide); + Square winnerKSq = pos.square(strongSide); + Square loserKSq = pos.square(weakSide); 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 +293,9 @@ 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. @@ -396,55 +309,44 @@ ScaleFactor Endgame::operator()(const Position& pos) const { // be detected even when the weaker side has some pawns. Bitboard pawns = pos.pieces(strongSide, PAWN); - File pawnFile = file_of(pos.list(strongSide)[0]); + File pawnsFile = file_of(lsb(pawns)); - // All pawns are on a single rook file ? - if ( (pawnFile == FILE_A || pawnFile == FILE_H) - && !(pawns & ~file_bb(pawnFile))) + // All pawns are on a single rook file? + if ( (pawnsFile == FILE_A || pawnsFile == FILE_H) + && !(pawns & ~file_bb(pawnsFile))) { - Square bishopSq = pos.list(strongSide)[0]; - Square queeningSq = relative_square(strongSide, pawnFile | RANK_8); - Square kingSq = pos.king_square(weakSide); + Square bishopSq = pos.square(strongSide); + Square queeningSq = relative_square(strongSide, make_square(pawnsFile, RANK_8)); + Square kingSq = pos.square(weakSide); if ( opposite_colors(queeningSq, bishopSq) - && abs(file_of(kingSq) - pawnFile) <= 1) - { - // The bishop has the wrong color, and the defending king is on the - // file of the pawn(s) or the adjacent file. Find the rank of the - // frontmost pawn. - Square pawnSq = frontmost_sq(strongSide, pawns); - - // 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(weakSide, kingSq) <= relative_rank(weakSide, pawnSq)) - return SCALE_FACTOR_DRAW; - } + && distance(queeningSq, kingSq) <= 1) + return SCALE_FACTOR_DRAW; } - // All pawns on same B or G file? Then potential draw - if ( (pawnFile == FILE_B || pawnFile == FILE_G) - && !(pos.pieces(PAWN) & ~file_bb(pawnFile)) + // If all the pawns are on the same B or G file, then it's potentially a draw + if ( (pawnsFile == FILE_B || pawnsFile == FILE_G) + && !(pos.pieces(PAWN) & ~file_bb(pawnsFile)) && pos.non_pawn_material(weakSide) == 0 && pos.count(weakSide) >= 1) { - // Get weakSide pawn that is closest to 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]; + Square strongKingSq = pos.square(strongSide); + Square weakKingSq = pos.square(weakSide); + Square bishopSq = pos.square(strongSide); - // 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 @@ -461,8 +363,8 @@ 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 { @@ -470,68 +372,49 @@ ScaleFactor Endgame::operator()(const Position& pos) const { assert(pos.count(weakSide) == 1); assert(pos.count(weakSide) >= 1); - Square kingSq = pos.king_square(weakSide); - Square rsq = pos.list(weakSide)[0]; + Square kingSq = pos.square(weakSide); + Square rsq = pos.square(weakSide); 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, pos.square(strongSide)) >= RANK_4 + && relative_rank(weakSide, rsq) == RANK_3 + && ( pos.pieces(weakSide, PAWN) + & pos.attacks_from(kingSq) + & pos.attacks_from(rsq, strongSide))) return SCALE_FACTOR_DRAW; return SCALE_FACTOR_NONE; } -/// 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.square(strongSide)); + Square bksq = normalize(pos, strongSide, pos.square(weakSide)); + Square wrsq = normalize(pos, strongSide, pos.square(strongSide)); + Square wpsq = normalize(pos, strongSide, pos.square(strongSide)); + Square brsq = normalize(pos, strongSide, pos.square(weakSide)); File f = file_of(wpsq); Rank r = rank_of(wpsq); - Square queeningSq = 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; @@ -539,15 +422,15 @@ 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 @@ -562,9 +445,9 @@ ScaleFactor Endgame::operator()(const Position& pos) const { // 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) + && bksq == wpsq + NORTH + && distance(wksq, wpsq) - tempo >= 2 + && distance(wksq, brsq) - tempo >= 2) return SCALE_FACTOR_DRAW; // Pawn on the 7th rank supported by the rook from behind usually wins if the @@ -574,32 +457,32 @@ 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 + NORTH) < distance(bksq, wpsq + NORTH) - 2 + tempo) + && ( distance(bksq, wrsq) + tempo >= 3 + || ( distance(wksq, queeningSq) < distance(bksq, wrsq) + tempo + && (distance(wksq, wpsq + NORTH) < distance(bksq, wrsq) + tempo)))) return ScaleFactor( SCALE_FACTOR_MAX - - 8 * 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; } @@ -613,11 +496,11 @@ ScaleFactor Endgame::operator()(const Position& pos) const { // Test for a rook pawn if (pos.pieces(PAWN) & (FileABB | FileHBB)) { - Square ksq = pos.king_square(weakSide); - Square bsq = pos.list(weakSide)[0]; - Square psq = pos.list(strongSide)[0]; + Square ksq = pos.square(weakSide); + Square bsq = pos.square(weakSide); + Square psq = pos.square(strongSide); Rank rk = relative_rank(strongSide, psq); - Square push = pawn_push(strongSide); + Direction push = pawn_push(strongSide); // If the pawn is on the 5th rank and the pawn (currently) is on // the same color square as the bishop then there is a chance of @@ -626,9 +509,9 @@ 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)) + if (d <= 2 && !(d == 0 && ksq == pos.square(strongSide) + 2 * push)) return ScaleFactor(24); else return ScaleFactor(48); @@ -639,27 +522,26 @@ 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 { assert(verify_material(pos, strongSide, RookValueMg, 2)); assert(verify_material(pos, weakSide, RookValueMg, 1)); - Square wpsq1 = pos.list(strongSide)[0]; - Square wpsq2 = pos.list(strongSide)[1]; - Square bksq = pos.king_square(weakSide); + Square wpsq1 = pos.squares(strongSide)[0]; + Square wpsq2 = pos.squares(strongSide)[1]; + Square bksq = pos.square(weakSide); // Does the stronger side have a passed pawn? if (pos.pawn_passed(strongSide, wpsq1) || pos.pawn_passed(strongSide, wpsq2)) @@ -667,18 +549,12 @@ 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) { - 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); - } + assert(r > RANK_1 && r < RANK_7); + return ScaleFactor(KRPPKRPScaleFactors[r]); } return SCALE_FACTOR_NONE; } @@ -693,45 +569,34 @@ ScaleFactor Endgame::operator()(const Position& pos) const { assert(pos.count(strongSide) >= 2); assert(verify_material(pos, weakSide, VALUE_ZERO, 0)); - Square ksq = pos.king_square(weakSide); + Square ksq = pos.square(weakSide); Bitboard pawns = pos.pieces(strongSide, PAWN); - // 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; - } + // If all pawns are ahead of the king, on a single rook file and + // the king is within one file of the pawns, it's a draw. + if ( !(pawns & ~forward_ranks_bb(weakSide, ksq)) + && !((pawns & ~FileABB) && (pawns & ~FileHBB)) + && distance(ksq, lsb(pawns)) <= 1) + return SCALE_FACTOR_DRAW; + return SCALE_FACTOR_NONE; } -/// 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 { assert(verify_material(pos, strongSide, BishopValueMg, 1)); assert(verify_material(pos, weakSide, BishopValueMg, 0)); - Square pawnSq = pos.list(strongSide)[0]; - Square strongBishopSq = pos.list(strongSide)[0]; - Square weakBishopSq = pos.list(weakSide)[0]; - Square weakKingSq = pos.king_square(weakSide); + Square pawnSq = pos.square(strongSide); + Square strongBishopSq = pos.square(strongSide); + Square weakBishopSq = pos.square(weakSide); + Square weakKingSq = pos.square(weakSide); // Case 1: Defending king blocks the pawn, and cannot be driven away if ( file_of(weakKingSq) == file_of(pawnSq) @@ -742,52 +607,28 @@ ScaleFactor Endgame::operator()(const Position& pos) const { // Case 2: Opposite colored bishops if (opposite_colors(strongBishopSq, weakBishopSq)) - { - // 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(strongSide, pawnSq) <= RANK_5) - return SCALE_FACTOR_DRAW; - else - { - Bitboard path = forward_bb(strongSide, pawnSq); - - if (path & pos.pieces(weakSide, KING)) - return SCALE_FACTOR_DRAW; + return SCALE_FACTOR_DRAW; - if ( (pos.attacks_from(weakBishopSq) & path) - && square_distance(weakBishopSq, pawnSq) >= 3) - return SCALE_FACTOR_DRAW; - } - } return SCALE_FACTOR_NONE; } -/// 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 { assert(verify_material(pos, strongSide, BishopValueMg, 2)); assert(verify_material(pos, weakSide, BishopValueMg, 0)); - Square wbsq = pos.list(strongSide)[0]; - Square bbsq = pos.list(weakSide)[0]; + Square wbsq = pos.square(strongSide); + Square bbsq = pos.square(weakSide); if (!opposite_colors(wbsq, bbsq)) return SCALE_FACTOR_NONE; - Square ksq = pos.king_square(weakSide); - Square psq1 = pos.list(strongSide)[0]; - Square psq2 = pos.list(strongSide)[1]; + Square ksq = pos.square(weakSide); + Square psq1 = pos.squares(strongSide)[0]; + Square psq2 = pos.squares(strongSide)[1]; Rank r1 = rank_of(psq1); Rank r2 = rank_of(psq2); Square blockSq1, blockSq2; @@ -795,19 +636,19 @@ 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)) @@ -816,14 +657,14 @@ 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 @@ -841,18 +682,18 @@ 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 { assert(verify_material(pos, strongSide, BishopValueMg, 1)); assert(verify_material(pos, weakSide, KnightValueMg, 0)); - Square pawnSq = pos.list(strongSide)[0]; - Square strongBishopSq = pos.list(strongSide)[0]; - Square weakKingSq = pos.king_square(weakSide); + Square pawnSq = pos.square(strongSide); + Square strongBishopSq = pos.square(strongSide); + Square weakKingSq = pos.square(weakSide); if ( file_of(weakKingSq) == file_of(pawnSq) && relative_rank(strongSide, pawnSq) < relative_rank(strongSide, weakKingSq) @@ -864,78 +705,60 @@ 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.square(strongSide)); + Square weakKingSq = normalize(pos, strongSide, pos.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 { - Square pawnSq = pos.list(strongSide)[0]; - Square bishopSq = pos.list(weakSide)[0]; - Square weakKingSq = pos.king_square(weakSide); + Square pawnSq = pos.square(strongSide); + Square bishopSq = pos.square(weakSide); + Square weakKingSq = pos.square(weakSide); // 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)); + if (forward_file_bb(strongSide, pawnSq) & pos.attacks_from(bishopSq)) + 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(); - - if (strongSide == BLACK) - { - wksq = ~wksq; - bksq = ~bksq; - psq = ~psq; - us = ~us; - } + // Assume strongSide is white and the pawn is on files A-D + Square wksq = normalize(pos, strongSide, pos.square(strongSide)); + Square bksq = normalize(pos, strongSide, pos.square(weakSide)); + Square psq = normalize(pos, strongSide, pos.square(strongSide)); - if (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. @@ -944,5 +767,5 @@ 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; }