X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fendgame.cpp;h=e52f9939e3eea38180315735578cfc40ab7c5b97;hp=4323a4209442d10601b9711018422435d3344fac;hb=67b0da83da343cb6046f2a2f088f7aa1a6276637;hpb=a4c11b71acc4aeab032128d4ba9d0d4ccd51aa20 diff --git a/src/endgame.cpp b/src/endgame.cpp index 4323a420..e52f9939 100644 --- a/src/endgame.cpp +++ b/src/endgame.cpp @@ -29,9 +29,9 @@ using std::string; namespace { - // Table used to drive the defending king towards the edge of the board + // Table used to drive the king towards the edge of the board // in KX vs K and KQ vs KR endgames. - const int MateTable[SQUARE_NB] = { + const 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, @@ -42,9 +42,9 @@ namespace { 100, 90, 80, 70, 70, 80, 90, 100, }; - // Table used to drive the defending king towards a corner square of the + // Table used to drive the king towards a corner square of the // right color in KBN vs K endgames. - const int KBNKMateTable[SQUARE_NB] = { + const 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, @@ -55,9 +55,30 @@ namespace { 130, 140, 150, 160, 170, 180, 190, 200 }; - // The attacking side is given a descending bonus based on distance between - // the two kings in basic endgames. - const int DistanceBonus[8] = { 0, 0, 100, 80, 60, 40, 20, 10 }; + // 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 }; + +#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; + } +#endif + + // 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 = mirror(sq); + + if (strongSide == BLACK) + sq = ~sq; + + return sq; + } // 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 @@ -68,8 +89,8 @@ namespace { assert(code.length() > 0 && code.length() < 8); assert(code[0] == 'K'); - string sides[] = { code.substr(code.find('K', 1)), // Weaker - code.substr(0, code.find('K', 1)) }; // Stronger + string sides[] = { code.substr(code.find('K', 1)), // Weak + code.substr(0, code.find('K', 1)) }; // Strong std::transform(sides[c].begin(), sides[c].end(), sides[c].begin(), tolower); @@ -102,6 +123,7 @@ Endgames::Endgames() { add("KNPK"); add("KNPKB"); add("KRPKR"); + add("KRPKB"); add("KBPKB"); add("KBPKN"); add("KBPPKB"); @@ -129,31 +151,27 @@ void Endgames::add(const string& code) { template<> Value Endgame::operator()(const Position& pos) const { - assert(pos.non_pawn_material(weakerSide) == VALUE_ZERO); - assert(!pos.count(weakerSide)); + assert(verify_material(pos, weakSide, VALUE_ZERO, 0)); + assert(!pos.checkers()); // Eval is never called when in check // Stalemate detection with lone king - if ( pos.side_to_move() == weakerSide - && !pos.checkers() - && !MoveList(pos).size()) { - return VALUE_DRAW; - } + if (pos.side_to_move() == weakSide && !MoveList(pos).size()) + return VALUE_DRAW; - Square winnerKSq = pos.king_square(strongerSide); - Square loserKSq = pos.king_square(weakerSide); + Square winnerKSq = pos.king_square(strongSide); + Square loserKSq = pos.king_square(weakSide); - Value result = pos.non_pawn_material(strongerSide) - + pos.count(strongerSide) * PawnValueEg - + MateTable[loserKSq] - + DistanceBonus[square_distance(winnerKSq, loserKSq)]; + Value result = pos.non_pawn_material(strongSide) + + pos.count(strongSide) * PawnValueEg + + PushToEdges[loserKSq] + + PushClose[square_distance(winnerKSq, loserKSq)]; - if ( pos.count(strongerSide) - || pos.count(strongerSide) - || pos.bishop_pair(strongerSide)) { - result += VALUE_KNOWN_WIN; - } + if ( pos.count(strongSide) + || pos.count(strongSide) + || pos.bishop_pair(strongSide)) + result += VALUE_KNOWN_WIN; - return strongerSide == pos.side_to_move() ? result : -result; + return strongSide == pos.side_to_move() ? result : -result; } @@ -162,31 +180,27 @@ Value Endgame::operator()(const Position& pos) const { template<> Value Endgame::operator()(const Position& pos) const { - assert(pos.non_pawn_material(strongerSide) == KnightValueMg + BishopValueMg); - assert(pos.non_pawn_material(weakerSide) == VALUE_ZERO); - assert(pos.count(strongerSide) == 1); - assert(pos.count(strongerSide) == 1); - assert(pos.count< PAWN>(strongerSide) == 0); - assert(pos.count< PAWN>(weakerSide ) == 0); + assert(verify_material(pos, strongSide, KnightValueMg + BishopValueMg, 0)); + assert(verify_material(pos, weakSide, VALUE_ZERO, 0)); - Square winnerKSq = pos.king_square(strongerSide); - Square loserKSq = pos.king_square(weakerSide); - Square bishopSq = pos.list(strongerSide)[0]; + Square winnerKSq = pos.king_square(strongSide); + 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. + // flip the kings so to drive 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 - + DistanceBonus[square_distance(winnerKSq, loserKSq)] - + KBNKMateTable[loserKSq]; + + PushClose[square_distance(winnerKSq, loserKSq)] + + PushToCorners[loserKSq]; - return strongerSide == pos.side_to_move() ? result : -result; + return strongSide == pos.side_to_move() ? result : -result; } @@ -194,42 +208,22 @@ Value Endgame::operator()(const Position& pos) const { template<> Value Endgame::operator()(const Position& pos) const { - assert(pos.non_pawn_material(strongerSide) == VALUE_ZERO); - assert(pos.non_pawn_material(weakerSide) == VALUE_ZERO); - assert(pos.count(strongerSide) == 1); - assert(pos.count(weakerSide ) == 0); + assert(verify_material(pos, strongSide, VALUE_ZERO, 1)); + assert(verify_material(pos, weakSide, VALUE_ZERO, 0)); - Square wksq, bksq, wpsq; - Color us; + // 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 (strongerSide == WHITE) - { - wksq = pos.king_square(WHITE); - bksq = pos.king_square(BLACK); - wpsq = pos.list(WHITE)[0]; - us = pos.side_to_move(); - } - else - { - wksq = ~pos.king_square(BLACK); - bksq = ~pos.king_square(WHITE); - wpsq = ~pos.list(BLACK)[0]; - us = ~pos.side_to_move(); - } + Color us = strongSide == pos.side_to_move() ? WHITE : BLACK; - if (file_of(wpsq) >= FILE_E) - { - wksq = mirror(wksq); - bksq = mirror(bksq); - wpsq = mirror(wpsq); - } - - if (!Bitbases::probe_kpk(wksq, wpsq, bksq, us)) + if (!Bitbases::probe_kpk(wksq, psq, bksq, us)) return VALUE_DRAW; - Value result = VALUE_KNOWN_WIN + PawnValueEg + Value(rank_of(wpsq)); + Value result = VALUE_KNOWN_WIN + PawnValueEg + Value(rank_of(psq)); - return strongerSide == pos.side_to_move() ? result : -result; + return strongSide == pos.side_to_move() ? result : -result; } @@ -240,55 +234,42 @@ Value Endgame::operator()(const Position& pos) const { template<> Value Endgame::operator()(const Position& pos) const { - assert(pos.non_pawn_material(strongerSide) == RookValueMg); - assert(pos.non_pawn_material(weakerSide) == 0); - assert(pos.count(strongerSide) == 0); - assert(pos.count(weakerSide ) == 1); - - Square wksq, wrsq, bksq, bpsq; - int tempo = (pos.side_to_move() == strongerSide); + assert(verify_material(pos, strongSide, RookValueMg, 0)); + assert(verify_material(pos, weakSide, VALUE_ZERO, 1)); - wksq = pos.king_square(strongerSide); - bksq = pos.king_square(weakerSide); - wrsq = pos.list(strongerSide)[0]; - bpsq = pos.list(weakerSide)[0]; + 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]); - if (strongerSide == BLACK) - { - wksq = ~wksq; - wrsq = ~wrsq; - bksq = ~bksq; - bpsq = ~bpsq; - } - - Square queeningSq = file_of(bpsq) | RANK_1; + Square queeningSq = 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 < bpsq && file_of(wksq) == file_of(bpsq)) - result = RookValueEg - Value(square_distance(wksq, bpsq)); + if (wksq < psq && file_of(wksq) == file_of(psq)) + result = RookValueEg - Value(square_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, bpsq) - (tempo ^ 1) >= 3 - && square_distance(bksq, wrsq) >= 3) - result = RookValueEg - Value(square_distance(wksq, bpsq)); + // 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)); // 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, bpsq) == 1 + && square_distance(bksq, psq) == 1 && rank_of(wksq) >= RANK_4 - && square_distance(wksq, bpsq) - tempo > 2) - result = Value(80 - square_distance(wksq, bpsq) * 8); + && square_distance(wksq, psq) > 2 + (pos.side_to_move() == strongSide)) + result = Value(80 - square_distance(wksq, psq) * 8); else result = Value(200) - - Value(square_distance(wksq, bpsq + DELTA_S) * 8) - + Value(square_distance(bksq, bpsq + DELTA_S) * 8) - + Value(square_distance(bpsq, queeningSq) * 8); + - Value(square_distance(wksq, psq + DELTA_S) * 8) + + Value(square_distance(bksq, psq + DELTA_S) * 8) + + Value(square_distance(psq, queeningSq) * 8); - return strongerSide == pos.side_to_move() ? result : -result; + return strongSide == pos.side_to_move() ? result : -result; } @@ -297,14 +278,11 @@ Value Endgame::operator()(const Position& pos) const { template<> Value Endgame::operator()(const Position& pos) const { - assert(pos.non_pawn_material(strongerSide) == RookValueMg); - assert(pos.non_pawn_material(weakerSide ) == BishopValueMg); - assert(pos.count(weakerSide ) == 1); - assert(pos.count< PAWN>(weakerSide ) == 0); - assert(pos.count< PAWN>(strongerSide) == 0); + assert(verify_material(pos, strongSide, RookValueMg, 0)); + assert(verify_material(pos, weakSide, BishopValueMg, 0)); - Value result = Value(MateTable[pos.king_square(weakerSide)]); - return strongerSide == pos.side_to_move() ? result : -result; + Value result = Value(PushToEdges[pos.king_square(weakSide)]); + return strongSide == pos.side_to_move() ? result : -result; } @@ -313,18 +291,13 @@ Value Endgame::operator()(const Position& pos) const { template<> Value Endgame::operator()(const Position& pos) const { - assert(pos.non_pawn_material(strongerSide) == RookValueMg); - assert(pos.non_pawn_material(weakerSide ) == KnightValueMg); - assert(pos.count(weakerSide ) == 1); - assert(pos.count< PAWN>(weakerSide ) == 0); - assert(pos.count< PAWN>(strongerSide) == 0); - - const int penalty[8] = { 0, 10, 14, 20, 30, 42, 58, 80 }; + assert(verify_material(pos, strongSide, RookValueMg, 0)); + assert(verify_material(pos, weakSide, KnightValueMg, 0)); - Square bksq = pos.king_square(weakerSide); - Square bnsq = pos.list(weakerSide)[0]; - Value result = Value(MateTable[bksq] + penalty[square_distance(bksq, bnsq)]); - return strongerSide == pos.side_to_move() ? result : -result; + Square bksq = pos.king_square(weakSide); + Square bnsq = pos.list(weakSide)[0]; + Value result = Value(PushToEdges[bksq] + PushAway[square_distance(bksq, bnsq)]); + return strongSide == pos.side_to_move() ? result : -result; } @@ -334,28 +307,21 @@ Value Endgame::operator()(const Position& pos) const { template<> Value Endgame::operator()(const Position& pos) const { - assert(pos.non_pawn_material(strongerSide) == QueenValueMg); - assert(pos.non_pawn_material(weakerSide ) == VALUE_ZERO); - assert(pos.count(strongerSide) == 0); - assert(pos.count(weakerSide ) == 1); + assert(verify_material(pos, strongSide, QueenValueMg, 0)); + assert(verify_material(pos, weakSide, VALUE_ZERO, 1)); - Square winnerKSq = pos.king_square(strongerSide); - Square loserKSq = pos.king_square(weakerSide); - Square pawnSq = pos.list(weakerSide)[0]; + Square winnerKSq = pos.king_square(strongSide); + Square loserKSq = pos.king_square(weakSide); + Square pawnSq = pos.list(weakSide)[0]; - Value result = QueenValueEg - - PawnValueEg - + DistanceBonus[square_distance(winnerKSq, loserKSq)]; + Value result = Value(PushClose[square_distance(winnerKSq, loserKSq)]); - if ( square_distance(loserKSq, pawnSq) == 1 - && relative_rank(weakerSide, pawnSq) == RANK_7) - { - File f = file_of(pawnSq); + if ( relative_rank(weakSide, pawnSq) != RANK_7 + || square_distance(loserKSq, pawnSq) != 1 + || !((FileABB | FileCBB | FileFBB | FileHBB) & pawnSq)) + result += QueenValueEg - PawnValueEg; - if (f == FILE_A || f == FILE_C || f == FILE_F || f == FILE_H) - result = Value(DistanceBonus[square_distance(winnerKSq, loserKSq)]); - } - return strongerSide == pos.side_to_move() ? result : -result; + return strongSide == pos.side_to_move() ? result : -result; } @@ -367,60 +333,48 @@ Value Endgame::operator()(const Position& pos) const { template<> Value Endgame::operator()(const Position& pos) const { - assert(pos.non_pawn_material(strongerSide) == QueenValueMg); - assert(pos.non_pawn_material(weakerSide ) == RookValueMg); - assert(pos.count(strongerSide) == 0); - assert(pos.count(weakerSide ) == 0); + assert(verify_material(pos, strongSide, QueenValueMg, 0)); + assert(verify_material(pos, weakSide, RookValueMg, 0)); - Square winnerKSq = pos.king_square(strongerSide); - Square loserKSq = pos.king_square(weakerSide); + Square winnerKSq = pos.king_square(strongSide); + Square loserKSq = pos.king_square(weakSide); Value result = QueenValueEg - RookValueEg - + MateTable[loserKSq] - + DistanceBonus[square_distance(winnerKSq, loserKSq)]; + + PushToEdges[loserKSq] + + PushClose[square_distance(winnerKSq, loserKSq)]; - return strongerSide == pos.side_to_move() ? result : -result; + return strongSide == pos.side_to_move() ? result : -result; } -template<> -Value Endgame::operator()(const Position& pos) const { - assert(pos.non_pawn_material(strongerSide) == 2 * BishopValueMg); - assert(pos.non_pawn_material(weakerSide ) == KnightValueMg); - assert(pos.count(strongerSide) == 2); - assert(pos.count(weakerSide ) == 1); - assert(!pos.pieces(PAWN)); +/// 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 - Value result = BishopValueEg; - Square wksq = pos.king_square(strongerSide); - Square bksq = pos.king_square(weakerSide); - Square nsq = pos.list(weakerSide)[0]; +template<> +Value Endgame::operator()(const Position& pos) const { - // Bonus for attacking king close to defending king - result += Value(DistanceBonus[square_distance(wksq, bksq)]); + assert(verify_material(pos, strongSide, 2 * BishopValueMg, 0)); + assert(verify_material(pos, weakSide, KnightValueMg, 0)); - // Bonus for driving the defending king and knight apart - result += Value(square_distance(bksq, nsq) * 32); + Square winnerKSq = pos.king_square(strongSide); + Square loserKSq = pos.king_square(weakSide); + Square knightSq = pos.list(weakSide)[0]; - // Bonus for restricting the knight's mobility - result += Value((8 - popcount(pos.attacks_from(nsq))) * 8); + Value result = VALUE_KNOWN_WIN + + PushToCorners[loserKSq] + + PushClose[square_distance(winnerKSq, loserKSq)] + + PushAway[square_distance(loserKSq, knightSq)]; - return strongerSide == pos.side_to_move() ? result : -result; + return strongSide == 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 Endgame::operator()(const Position&) const { - return VALUE_DRAW; -} +/// 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; } -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 /// a bishop of the wrong color. If such a draw is detected, SCALE_FACTOR_DRAW @@ -429,70 +383,61 @@ Value Endgame::operator()(const Position&) const { template<> ScaleFactor Endgame::operator()(const Position& pos) const { - assert(pos.non_pawn_material(strongerSide) == BishopValueMg); - assert(pos.count(strongerSide) == 1); - assert(pos.count< PAWN>(strongerSide) >= 1); + assert(pos.non_pawn_material(strongSide) == BishopValueMg); + assert(pos.count(strongSide) >= 1); - // No assertions about the material of weakerSide, because we want draws to + // No assertions about the material of weakSide, because we want draws to // be detected even when the weaker side has some pawns. - Bitboard pawns = pos.pieces(strongerSide, PAWN); - File pawnFile = file_of(pos.list(strongerSide)[0]); + Bitboard pawns = pos.pieces(strongSide, PAWN); + File pawnFile = file_of(pos.list(strongSide)[0]); // All pawns are on a single rook file ? if ( (pawnFile == FILE_A || pawnFile == FILE_H) && !(pawns & ~file_bb(pawnFile))) { - Square bishopSq = pos.list(strongerSide)[0]; - Square queeningSq = relative_square(strongerSide, pawnFile | RANK_8); - Square kingSq = pos.king_square(weakerSide); + Square bishopSq = pos.list(strongSide)[0]; + Square queeningSq = relative_square(strongSide, pawnFile | RANK_8); + Square kingSq = pos.king_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. - Rank rank; - if (strongerSide == WHITE) - { - for (rank = RANK_7; !(rank_bb(rank) & pawns); rank--) {} - assert(rank >= RANK_2 && rank <= RANK_7); - } - else - { - for (rank = RANK_2; !(rank_bb(rank) & pawns); 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 SCALE_FACTOR_DRAW; - } + && square_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)) - && pos.non_pawn_material(weakerSide) == 0 - && pos.count(weakerSide) >= 1) + && pos.non_pawn_material(weakSide) == 0 + && pos.count(weakSide) >= 1) { - // Get weaker pawn closest to opponent's queening square - Bitboard wkPawns = pos.pieces(weakerSide, PAWN); - Square weakerPawnSq = strongerSide == WHITE ? msb(wkPawns) : lsb(wkPawns); - - Square strongerKingSq = pos.king_square(strongerSide); - Square weakerKingSq = pos.king_square(weakerSide); - Square bishopSq = pos.list(strongerSide)[0]; - - // Draw if weaker pawn is on rank 7, bishop can't attack the pawn, and - // weaker king can stop opposing opponent's king from penetrating. - if ( relative_rank(strongerSide, weakerPawnSq) == RANK_7 - && opposite_colors(bishopSq, weakerPawnSq) - && square_distance(weakerPawnSq, weakerKingSq) <= square_distance(weakerPawnSq, strongerKingSq)) - return SCALE_FACTOR_DRAW; + // Get weakSide pawn that is closest to 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 + // 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); + + // Draw if the weak king is on it's 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 + // and positions where qsearch will immediately correct the + // problem such as 8/4k1p1/6P1/1K6/3B4/8/8/8 w) + if ( relative_rank(strongSide, weakKingSq) >= RANK_7 + && weakKingDist <= 2 + && weakKingDist <= strongKingDist) + return SCALE_FACTOR_DRAW; + } } return SCALE_FACTOR_NONE; @@ -504,23 +449,21 @@ ScaleFactor Endgame::operator()(const Position& pos) const { template<> ScaleFactor Endgame::operator()(const Position& pos) const { - assert(pos.non_pawn_material(strongerSide) == QueenValueMg); - assert(pos.count(strongerSide) == 1); - assert(pos.count< PAWN>(strongerSide) == 0); - assert(pos.count< ROOK>(weakerSide ) == 1); - assert(pos.count< PAWN>(weakerSide ) >= 1); - - Square kingSq = pos.king_square(weakerSide); - if ( relative_rank(weakerSide, kingSq) <= RANK_2 - && relative_rank(weakerSide, pos.king_square(strongerSide)) >= RANK_4 - && (pos.pieces(weakerSide, ROOK) & rank_bb(relative_rank(weakerSide, RANK_3))) - && (pos.pieces(weakerSide, PAWN) & rank_bb(relative_rank(weakerSide, RANK_2))) - && (pos.attacks_from(kingSq) & pos.pieces(weakerSide, PAWN))) - { - Square rsq = pos.list(weakerSide)[0]; - if (pos.attacks_from(rsq, strongerSide) & pos.pieces(weakerSide, PAWN)) + assert(verify_material(pos, strongSide, QueenValueMg, 0)); + assert(pos.count(weakSide) == 1); + assert(pos.count(weakSide) >= 1); + + Square kingSq = pos.king_square(weakSide); + Square rsq = pos.list(weakSide)[0]; + + if ( relative_rank(weakSide, kingSq) <= RANK_2 + && relative_rank(weakSide, pos.king_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; } @@ -534,40 +477,20 @@ ScaleFactor Endgame::operator()(const Position& pos) const { template<> ScaleFactor Endgame::operator()(const Position& pos) const { - assert(pos.non_pawn_material(strongerSide) == RookValueMg); - assert(pos.non_pawn_material(weakerSide) == RookValueMg); - assert(pos.count(strongerSide) == 1); - assert(pos.count(weakerSide ) == 0); + assert(verify_material(pos, strongSide, RookValueMg, 1)); + assert(verify_material(pos, weakSide, RookValueMg, 0)); - Square wksq = pos.king_square(strongerSide); - Square bksq = pos.king_square(weakerSide); - Square wrsq = pos.list(strongerSide)[0]; - Square wpsq = pos.list(strongerSide)[0]; - Square brsq = pos.list(weakerSide)[0]; - - // Orient the board in such a way that the stronger side is white, and the - // pawn is on the left half of the board. - if (strongerSide == BLACK) - { - wksq = ~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; - int tempo = (pos.side_to_move() == strongerSide); + 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. @@ -645,6 +568,49 @@ ScaleFactor Endgame::operator()(const Position& pos) const { return SCALE_FACTOR_NONE; } +template<> +ScaleFactor Endgame::operator()(const Position& pos) const { + + assert(verify_material(pos, strongSide, RookValueMg, 1)); + assert(verify_material(pos, weakSide, BishopValueMg, 0)); + + // 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]; + Rank rk = relative_rank(strongSide, psq); + Square 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 + // a fortress. Depending on the king position give a moderate + // reduction or a stronger one if the defending king is near the + // corner but not trapped there. + if (rk == RANK_5 && !opposite_colors(bsq, psq)) + { + int d = square_distance(psq + 3 * push, ksq); + + if (d <= 2 && !(d == 0 && ksq == pos.king_square(strongSide) + 2 * push)) + return ScaleFactor(24); + else + return ScaleFactor(48); + } + + // When the pawn has moved to the 6th rank we can be fairly sure + // it's drawn if the bishop attacks the square in front of the + // pawn from a reasonable distance and the defending king is near + // the corner + if ( rk == RANK_6 + && square_distance(psq + 2 * push, ksq) <= 1 + && (PseudoAttacks[BISHOP][bsq] & (psq + push)) + && file_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 @@ -652,25 +618,22 @@ ScaleFactor Endgame::operator()(const Position& pos) const { template<> ScaleFactor Endgame::operator()(const Position& pos) const { - assert(pos.non_pawn_material(strongerSide) == RookValueMg); - assert(pos.non_pawn_material(weakerSide) == RookValueMg); - assert(pos.count(strongerSide) == 2); - assert(pos.count(weakerSide ) == 1); + assert(verify_material(pos, strongSide, RookValueMg, 2)); + assert(verify_material(pos, weakSide, RookValueMg, 1)); - Square wpsq1 = pos.list(strongerSide)[0]; - Square wpsq2 = pos.list(strongerSide)[1]; - Square bksq = pos.king_square(weakerSide); + Square wpsq1 = pos.list(strongSide)[0]; + Square wpsq2 = pos.list(strongSide)[1]; + Square bksq = pos.king_square(weakSide); // Does the stronger side have a passed pawn? - if ( pos.pawn_is_passed(strongerSide, wpsq1) - || pos.pawn_is_passed(strongerSide, wpsq2)) + if (pos.pawn_passed(strongSide, wpsq1) || pos.pawn_passed(strongSide, wpsq2)) return SCALE_FACTOR_NONE; - Rank r = std::max(relative_rank(strongerSide, wpsq1), relative_rank(strongerSide, wpsq2)); + Rank r = std::max(relative_rank(strongSide, wpsq1), relative_rank(strongSide, wpsq2)); if ( file_distance(bksq, wpsq1) <= 1 && file_distance(bksq, wpsq2) <= 1 - && relative_rank(strongerSide, bksq) > r) + && relative_rank(strongSide, bksq) > r) { switch (r) { case RANK_2: return ScaleFactor(10); @@ -690,32 +653,21 @@ ScaleFactor Endgame::operator()(const Position& pos) const { template<> ScaleFactor Endgame::operator()(const Position& pos) const { - assert(pos.non_pawn_material(strongerSide) == VALUE_ZERO); - assert(pos.non_pawn_material(weakerSide) == VALUE_ZERO); - assert(pos.count(strongerSide) >= 2); - assert(pos.count(weakerSide ) == 0); + assert(pos.non_pawn_material(strongSide) == VALUE_ZERO); + assert(pos.count(strongSide) >= 2); + assert(verify_material(pos, weakSide, VALUE_ZERO, 0)); - Square ksq = pos.king_square(weakerSide); - Bitboard pawns = pos.pieces(strongerSide, PAWN); + 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, all pawns are on a single + // rook file and the king is within one file of the pawns then draw. + if ( !(pawns & ~in_front_bb(weakSide, rank_of(ksq))) + && !((pawns & ~FileABB) && (pawns & ~FileHBB)) + && file_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(strongerSide, SQ_A8)) <= 1 - || ( file_of(ksq) == FILE_A - && !(in_front_bb(strongerSide, 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(strongerSide, SQ_H8)) <= 1 - || ( file_of(ksq) == FILE_H - && !(in_front_bb(strongerSide, rank_of(ksq)) & pawns))) - return SCALE_FACTOR_DRAW; - } return SCALE_FACTOR_NONE; } @@ -727,27 +679,23 @@ ScaleFactor Endgame::operator()(const Position& pos) const { template<> ScaleFactor Endgame::operator()(const Position& pos) const { - assert(pos.non_pawn_material(strongerSide) == BishopValueMg); - assert(pos.non_pawn_material(weakerSide ) == BishopValueMg); - assert(pos.count(strongerSide) == 1); - assert(pos.count(weakerSide ) == 1); - assert(pos.count< PAWN>(strongerSide) == 1); - assert(pos.count< PAWN>(weakerSide ) == 0); + assert(verify_material(pos, strongSide, BishopValueMg, 1)); + assert(verify_material(pos, weakSide, BishopValueMg, 0)); - Square pawnSq = pos.list(strongerSide)[0]; - Square strongerBishopSq = pos.list(strongerSide)[0]; - Square weakerBishopSq = pos.list(weakerSide)[0]; - Square weakerKingSq = pos.king_square(weakerSide); + Square pawnSq = pos.list(strongSide)[0]; + Square strongBishopSq = pos.list(strongSide)[0]; + Square weakBishopSq = pos.list(weakSide)[0]; + Square weakKingSq = pos.king_square(weakSide); // Case 1: Defending king blocks the pawn, and cannot be driven away - if ( file_of(weakerKingSq) == file_of(pawnSq) - && relative_rank(strongerSide, pawnSq) < relative_rank(strongerSide, weakerKingSq) - && ( opposite_colors(weakerKingSq, strongerBishopSq) - || relative_rank(strongerSide, weakerKingSq) <= RANK_6)) + if ( file_of(weakKingSq) == file_of(pawnSq) + && relative_rank(strongSide, pawnSq) < relative_rank(strongSide, weakKingSq) + && ( opposite_colors(weakKingSq, strongBishopSq) + || relative_rank(strongSide, weakKingSq) <= RANK_6)) return SCALE_FACTOR_DRAW; // Case 2: Opposite colored bishops - if (opposite_colors(strongerBishopSq, weakerBishopSq)) + if (opposite_colors(strongBishopSq, weakBishopSq)) { // We assume that the position is drawn in the following three situations: // @@ -759,17 +707,17 @@ ScaleFactor Endgame::operator()(const Position& pos) const { // These rules are probably not perfect, but in practice they work // reasonably well. - if (relative_rank(strongerSide, pawnSq) <= RANK_5) + if (relative_rank(strongSide, pawnSq) <= RANK_5) return SCALE_FACTOR_DRAW; else { - Bitboard path = forward_bb(strongerSide, pawnSq); + Bitboard path = forward_bb(strongSide, pawnSq); - if (path & pos.pieces(weakerSide, KING)) + if (path & pos.pieces(weakSide, KING)) return SCALE_FACTOR_DRAW; - if ( (pos.attacks_from(weakerBishopSq) & path) - && square_distance(weakerBishopSq, pawnSq) >= 3) + if ( (pos.attacks_from(weakBishopSq) & path) + && square_distance(weakBishopSq, pawnSq) >= 3) return SCALE_FACTOR_DRAW; } } @@ -782,34 +730,30 @@ ScaleFactor Endgame::operator()(const Position& pos) const { template<> ScaleFactor Endgame::operator()(const Position& pos) const { - assert(pos.non_pawn_material(strongerSide) == BishopValueMg); - assert(pos.non_pawn_material(weakerSide ) == BishopValueMg); - assert(pos.count(strongerSide) == 1); - assert(pos.count(weakerSide ) == 1); - assert(pos.count< PAWN>(strongerSide) == 2); - assert(pos.count< PAWN>(weakerSide ) == 0); + assert(verify_material(pos, strongSide, BishopValueMg, 2)); + assert(verify_material(pos, weakSide, BishopValueMg, 0)); - Square wbsq = pos.list(strongerSide)[0]; - Square bbsq = pos.list(weakerSide)[0]; + Square wbsq = pos.list(strongSide)[0]; + Square bbsq = pos.list(weakSide)[0]; if (!opposite_colors(wbsq, bbsq)) return SCALE_FACTOR_NONE; - Square ksq = pos.king_square(weakerSide); - Square psq1 = pos.list(strongerSide)[0]; - Square psq2 = pos.list(strongerSide)[1]; + Square ksq = pos.king_square(weakSide); + Square psq1 = pos.list(strongSide)[0]; + Square psq2 = pos.list(strongSide)[1]; Rank r1 = rank_of(psq1); Rank r2 = rank_of(psq2); Square blockSq1, blockSq2; - if (relative_rank(strongerSide, psq1) > relative_rank(strongerSide, psq2)) + if (relative_rank(strongSide, psq1) > relative_rank(strongSide, psq2)) { - blockSq1 = psq1 + pawn_push(strongerSide); + blockSq1 = psq1 + pawn_push(strongSide); blockSq2 = file_of(psq2) | rank_of(psq1); } else { - blockSq1 = psq2 + pawn_push(strongerSide); + blockSq1 = psq2 + pawn_push(strongSide); blockSq2 = file_of(psq1) | rank_of(psq2); } @@ -819,7 +763,7 @@ ScaleFactor Endgame::operator()(const Position& pos) const { // Both pawns are on the same file. Easy draw if defender firmly controls // some square in the frontmost pawn's path. if ( file_of(ksq) == file_of(blockSq1) - && relative_rank(strongerSide, ksq) >= relative_rank(strongerSide, blockSq1) + && relative_rank(strongSide, ksq) >= relative_rank(strongSide, blockSq1) && opposite_colors(ksq, wbsq)) return SCALE_FACTOR_DRAW; else @@ -832,14 +776,14 @@ ScaleFactor Endgame::operator()(const Position& pos) const { if ( ksq == blockSq1 && opposite_colors(ksq, wbsq) && ( bbsq == blockSq2 - || (pos.attacks_from(blockSq2) & pos.pieces(weakerSide, BISHOP)) + || (pos.attacks_from(blockSq2) & pos.pieces(weakSide, BISHOP)) || abs(r1 - r2) >= 2)) return SCALE_FACTOR_DRAW; else if ( ksq == blockSq2 && opposite_colors(ksq, wbsq) && ( bbsq == blockSq1 - || (pos.attacks_from(blockSq1) & pos.pieces(weakerSide, BISHOP)))) + || (pos.attacks_from(blockSq1) & pos.pieces(weakSide, BISHOP)))) return SCALE_FACTOR_DRAW; else return SCALE_FACTOR_NONE; @@ -857,21 +801,17 @@ ScaleFactor Endgame::operator()(const Position& pos) const { template<> ScaleFactor Endgame::operator()(const Position& pos) const { - assert(pos.non_pawn_material(strongerSide) == BishopValueMg); - assert(pos.non_pawn_material(weakerSide ) == KnightValueMg); - assert(pos.count(strongerSide) == 1); - assert(pos.count(weakerSide ) == 1); - assert(pos.count< PAWN>(strongerSide) == 1); - assert(pos.count< PAWN>(weakerSide ) == 0); - - Square pawnSq = pos.list(strongerSide)[0]; - Square strongerBishopSq = pos.list(strongerSide)[0]; - Square weakerKingSq = pos.king_square(weakerSide); - - if ( file_of(weakerKingSq) == file_of(pawnSq) - && relative_rank(strongerSide, pawnSq) < relative_rank(strongerSide, weakerKingSq) - && ( opposite_colors(weakerKingSq, strongerBishopSq) - || relative_rank(strongerSide, weakerKingSq) <= RANK_6)) + 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); + + if ( file_of(weakKingSq) == file_of(pawnSq) + && relative_rank(strongSide, pawnSq) < relative_rank(strongSide, weakKingSq) + && ( opposite_colors(weakKingSq, strongBishopSq) + || relative_rank(strongSide, weakKingSq) <= RANK_6)) return SCALE_FACTOR_DRAW; return SCALE_FACTOR_NONE; @@ -884,21 +824,14 @@ ScaleFactor Endgame::operator()(const Position& pos) const { template<> ScaleFactor Endgame::operator()(const Position& pos) const { - assert(pos.non_pawn_material(strongerSide) == KnightValueMg); - assert(pos.non_pawn_material(weakerSide ) == VALUE_ZERO); - assert(pos.count(strongerSide) == 1); - assert(pos.count< PAWN>(strongerSide) == 1); - assert(pos.count< PAWN>(weakerSide ) == 0); + assert(verify_material(pos, strongSide, KnightValueMg, 1)); + assert(verify_material(pos, weakSide, VALUE_ZERO, 0)); - Square pawnSq = pos.list(strongerSide)[0]; - Square weakerKingSq = pos.king_square(weakerSide); - - if ( pawnSq == relative_square(strongerSide, SQ_A7) - && square_distance(weakerKingSq, relative_square(strongerSide, 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(strongerSide, SQ_H7) - && square_distance(weakerKingSq, relative_square(strongerSide, SQ_H8)) <= 1) + if (pawnSq == SQ_A7 && square_distance(SQ_A8, weakKingSq) <= 1) return SCALE_FACTOR_DRAW; return SCALE_FACTOR_NONE; @@ -910,14 +843,14 @@ ScaleFactor Endgame::operator()(const Position& pos) const { template<> ScaleFactor Endgame::operator()(const Position& pos) const { - Square pawnSq = pos.list(strongerSide)[0]; - Square bishopSq = pos.list(weakerSide)[0]; - Square weakerKingSq = pos.king_square(weakerSide); + Square pawnSq = pos.list(strongSide)[0]; + Square bishopSq = pos.list(weakSide)[0]; + Square weakKingSq = pos.king_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(strongerSide, pawnSq) & pos.attacks_from(bishopSq)) - return ScaleFactor(square_distance(weakerKingSq, pawnSq)); + if (forward_bb(strongSide, pawnSq) & pos.attacks_from(bishopSq)) + return ScaleFactor(square_distance(weakKingSq, pawnSq)); return SCALE_FACTOR_NONE; } @@ -931,38 +864,22 @@ ScaleFactor Endgame::operator()(const Position& pos) const { template<> ScaleFactor Endgame::operator()(const Position& pos) const { - assert(pos.non_pawn_material(strongerSide) == VALUE_ZERO); - assert(pos.non_pawn_material(weakerSide ) == VALUE_ZERO); - assert(pos.count(WHITE) == 1); - assert(pos.count(BLACK) == 1); + assert(verify_material(pos, strongSide, VALUE_ZERO, 1)); + assert(verify_material(pos, weakSide, VALUE_ZERO, 1)); - Square wksq = pos.king_square(strongerSide); - Square bksq = pos.king_square(weakerSide); - Square wpsq = pos.list(strongerSide)[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 (strongerSide == BLACK) - { - wksq = ~wksq; - bksq = ~bksq; - wpsq = ~wpsq; - us = ~us; - } - - if (file_of(wpsq) >= FILE_E) - { - wksq = mirror(wksq); - bksq = mirror(bksq); - wpsq = mirror(wpsq); - } + 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. - if ( rank_of(wpsq) >= RANK_5 - && file_of(wpsq) != FILE_A) + if (rank_of(psq) >= RANK_5 && file_of(psq) != FILE_A) return SCALE_FACTOR_NONE; // 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, wpsq, bksq, us) ? SCALE_FACTOR_NONE : SCALE_FACTOR_DRAW; + return Bitbases::probe_kpk(wksq, psq, bksq, us) ? SCALE_FACTOR_NONE : SCALE_FACTOR_DRAW; }