X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fendgame.cpp;h=c8be21983dd7064a7a06c1ce66d04c420d4d3a96;hp=3e01259c9745b01d90c0e9731f5bf2a6727fdf20;hb=32edb1d009e09a9442cb7393920e072ffd08005d;hpb=fc3af7c4fbeaa3c5b85424077829223f9d18184e diff --git a/src/endgame.cpp b/src/endgame.cpp index 3e01259c..c8be2198 100644 --- a/src/endgame.cpp +++ b/src/endgame.cpp @@ -1,8 +1,6 @@ /* Stockfish, a UCI chess playing engine derived from Glaurung 2.1 - Copyright (C) 2004-2008 Tord Romstad (Glaurung author) - Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad - Copyright (C) 2015-2018 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad + Copyright (C) 2004-2020 The Stockfish developers (see AUTHORS file) Stockfish is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by @@ -18,49 +16,31 @@ along with this program. If not, see . */ -#include #include #include "bitboard.h" #include "endgame.h" #include "movegen.h" -using std::string; - namespace { - // Table used to drive the king towards the edge of the board + // Used to drive the king towards the edge of the board // in KX vs K and KQ vs KR endgames. - 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, - 70, 50, 30, 20, 20, 30, 50, 70, - 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 - }; - - // Table used to drive the king towards a corner square of the - // right color in KBN vs K endgames. - 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, - 170, 160, 140, 120, 110, 140, 150, 160, - 160, 150, 140, 110, 120, 140, 160, 170, - 150, 140, 125, 140, 140, 155, 170, 180, - 140, 130, 140, 150, 160, 170, 180, 190, - 130, 140, 150, 160, 170, 180, 190, 200 - }; - - // Tables used to drive a piece towards or away from another piece - 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 }; + // Values range from 27 (center squares) to 90 (in the corners) + inline int push_to_edge(Square s) { + int rd = edge_distance(rank_of(s)), fd = edge_distance(file_of(s)); + return 90 - (7 * fd * fd / 2 + 7 * rd * rd / 2); + } + + // Used to drive the king towards A1H8 corners in KBN vs K endgames. + // Values range from 0 on A8H1 diagonal to 7 in A1H8 corners + inline int push_to_corner(Square s) { + return abs(7 - rank_of(s) - file_of(s)); + } + + // Drive a piece close to or away from another piece + inline int push_close(Square s1, Square s2) { return 140 - 20 * distance(s1, s2); } + inline int push_away(Square s1, Square s2) { return 120 - push_close(s1, s2); } #ifndef NDEBUG bool verify_material(const Position& pos, Color c, Value npm, int pawnsCnt) { @@ -75,38 +55,37 @@ namespace { assert(pos.count(strongSide) == 1); if (file_of(pos.square(strongSide)) >= FILE_E) - sq = Square(sq ^ 7); // Mirror SQ_H1 -> SQ_A1 - - if (strongSide == BLACK) - sq = ~sq; + sq = flip_file(sq); - return sq; + return strongSide == WHITE ? sq : flip_rank(sq); } } // namespace -/// Endgames members definitions +namespace Endgames { -Endgames::Endgames() { + std::pair, Map> maps; - add("KPK"); - add("KNNK"); - add("KBNK"); - add("KRKP"); - add("KRKB"); - add("KRKN"); - add("KQKP"); - add("KQKR"); + void init() { - add("KNPK"); - add("KNPKB"); - add("KRPKR"); - add("KRPKB"); - add("KBPKB"); - add("KBPKN"); - add("KBPPKB"); - add("KRPPKRP"); + add("KPK"); + add("KNNK"); + add("KBNK"); + add("KRKP"); + add("KRKB"); + add("KRKN"); + add("KQKP"); + add("KQKR"); + add("KNNKP"); + + add("KRPKR"); + add("KRPKB"); + add("KBPKB"); + add("KBPKN"); + add("KBPPKB"); + add("KRPPKRP"); + } } @@ -124,55 +103,50 @@ Value Endgame::operator()(const Position& pos) const { if (pos.side_to_move() == weakSide && !MoveList(pos).size()) return VALUE_DRAW; - Square winnerKSq = pos.square(strongSide); - Square loserKSq = pos.square(weakSide); + Square strongKing = pos.square(strongSide); + Square weakKing = pos.square(weakSide); Value result = pos.non_pawn_material(strongSide) + pos.count(strongSide) * PawnValueEg - + PushToEdges[loserKSq] - + PushClose[distance(winnerKSq, loserKSq)]; + + push_to_edge(weakKing) + + push_close(strongKing, weakKing); if ( pos.count(strongSide) || pos.count(strongSide) ||(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); + result = std::min(result + VALUE_KNOWN_WIN, VALUE_TB_WIN_IN_MAX_PLY - 1); return strongSide == pos.side_to_move() ? result : -result; } /// Mate with KBN vs K. This is similar to KX vs K, but we have to drive the -/// defending king towards a corner square of the right color. +/// defending king towards a corner square that our bishop attacks. template<> 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.square(strongSide); - Square loserKSq = pos.square(weakSide); - Square bishopSq = pos.square(strongSide); + Square strongKing = pos.square(strongSide); + Square strongBishop = pos.square(strongSide); + Square weakKing = pos.square(weakSide); - // 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 = ~winnerKSq; - loserKSq = ~loserKSq; - } + // If our bishop does not attack A1/H8, we flip the enemy king square + // to drive to opposite corners (A8/H1). - Value result = VALUE_KNOWN_WIN - + PushClose[distance(winnerKSq, loserKSq)] - + PushToCorners[loserKSq]; + Value result = (VALUE_KNOWN_WIN + 3520) + + push_close(strongKing, weakKing) + + 420 * push_to_corner(opposite_colors(strongBishop, SQ_A1) ? flip_file(weakKing) : weakKing); + assert(abs(result) < VALUE_TB_WIN_IN_MAX_PLY); return strongSide == pos.side_to_move() ? result : -result; } -/// KP vs K. This endgame is evaluated with the help of a bitbase. +/// KP vs K. This endgame is evaluated with the help of a bitbase template<> Value Endgame::operator()(const Position& pos) const { @@ -180,16 +154,16 @@ Value Endgame::operator()(const Position& pos) const { assert(verify_material(pos, weakSide, VALUE_ZERO, 0)); // 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)); + Square strongKing = normalize(pos, strongSide, pos.square(strongSide)); + Square strongPawn = normalize(pos, strongSide, pos.square(strongSide)); + Square weakKing = normalize(pos, strongSide, pos.square(weakSide)); Color us = strongSide == pos.side_to_move() ? WHITE : BLACK; - if (!Bitbases::probe(wksq, psq, bksq, us)) + if (!Bitbases::probe(strongKing, strongPawn, weakKing, us)) return VALUE_DRAW; - Value result = VALUE_KNOWN_WIN + PawnValueEg + Value(rank_of(psq)); + Value result = VALUE_KNOWN_WIN + PawnValueEg + Value(rank_of(strongPawn)); return strongSide == pos.side_to_move() ? result : -result; } @@ -205,42 +179,41 @@ Value Endgame::operator()(const Position& pos) const { assert(verify_material(pos, strongSide, RookValueMg, 0)); assert(verify_material(pos, weakSide, VALUE_ZERO, 1)); - 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)); - - Square queeningSq = make_square(file_of(psq), RANK_1); + Square strongKing = pos.square(strongSide); + Square weakKing = pos.square(weakSide); + Square strongRook = pos.square(strongSide); + Square weakPawn = pos.square(weakSide); + Square queeningSquare = make_square(file_of(weakPawn), relative_rank(weakSide, RANK_8)); Value result; // If the stronger side's king is in front of the pawn, it's a win - if (forward_file_bb(WHITE, wksq) & psq) - result = RookValueEg - distance(wksq, psq); + if (forward_file_bb(strongSide, strongKing) & weakPawn) + result = RookValueEg - distance(strongKing, weakPawn); // If the weaker side's king is too far from the pawn and the rook, // it's a win. - else if ( distance(bksq, psq) >= 3 + (pos.side_to_move() == weakSide) - && distance(bksq, rsq) >= 3) - result = RookValueEg - distance(wksq, psq); + else if ( distance(weakKing, weakPawn) >= 3 + (pos.side_to_move() == weakSide) + && distance(weakKing, strongRook) >= 3) + result = RookValueEg - distance(strongKing, weakPawn); // If the pawn is far advanced and supported by the defending king, // the position is drawish - else if ( rank_of(bksq) <= RANK_3 - && distance(bksq, psq) == 1 - && rank_of(wksq) >= RANK_4 - && distance(wksq, psq) > 2 + (pos.side_to_move() == strongSide)) - result = Value(80) - 8 * distance(wksq, psq); + else if ( relative_rank(strongSide, weakKing) <= RANK_3 + && distance(weakKing, weakPawn) == 1 + && relative_rank(strongSide, strongKing) >= RANK_4 + && distance(strongKing, weakPawn) > 2 + (pos.side_to_move() == strongSide)) + result = Value(80) - 8 * distance(strongKing, weakPawn); else - result = Value(200) - 8 * ( distance(wksq, psq + SOUTH) - - distance(bksq, psq + SOUTH) - - distance(psq, queeningSq)); + result = Value(200) - 8 * ( distance(strongKing, weakPawn + pawn_push(weakSide)) + - distance(weakKing, weakPawn + pawn_push(weakSide)) + - distance(weakPawn, queeningSquare)); 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 { @@ -248,7 +221,7 @@ 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.square(weakSide)]); + Value result = Value(push_to_edge(pos.square(weakSide))); return strongSide == pos.side_to_move() ? result : -result; } @@ -261,9 +234,9 @@ Value Endgame::operator()(const Position& pos) const { assert(verify_material(pos, strongSide, RookValueMg, 0)); assert(verify_material(pos, weakSide, KnightValueMg, 0)); - Square bksq = pos.square(weakSide); - Square bnsq = pos.square(weakSide); - Value result = Value(PushToEdges[bksq] + PushAway[distance(bksq, bnsq)]); + Square weakKing = pos.square(weakSide); + Square weakKnight = pos.square(weakSide); + Value result = Value(push_to_edge(weakKing) + push_away(weakKing, weakKnight)); return strongSide == pos.side_to_move() ? result : -result; } @@ -278,22 +251,22 @@ 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.square(strongSide); - Square loserKSq = pos.square(weakSide); - Square pawnSq = pos.square(weakSide); + Square strongKing = pos.square(strongSide); + Square weakKing = pos.square(weakSide); + Square weakPawn = pos.square(weakSide); - Value result = Value(PushClose[distance(winnerKSq, loserKSq)]); + Value result = Value(push_close(strongKing, weakKing)); - if ( relative_rank(weakSide, pawnSq) != RANK_7 - || distance(loserKSq, pawnSq) != 1 - || !((FileABB | FileCBB | FileFBB | FileHBB) & pawnSq)) + if ( relative_rank(weakSide, weakPawn) != RANK_7 + || distance(weakKing, weakPawn) != 1 + || ((FileBBB | FileDBB | FileEBB | FileGBB) & weakPawn)) result += QueenValueEg - PawnValueEg; return strongSide == pos.side_to_move() ? result : -result; } -/// KQ vs KR. This is almost identical to KX vs K: We give the attacking +/// 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 win KQ vs KR. @@ -303,13 +276,32 @@ Value Endgame::operator()(const Position& pos) const { assert(verify_material(pos, strongSide, QueenValueMg, 0)); assert(verify_material(pos, weakSide, RookValueMg, 0)); - Square winnerKSq = pos.square(strongSide); - Square loserKSq = pos.square(weakSide); + Square strongKing = pos.square(strongSide); + Square weakKing = pos.square(weakSide); Value result = QueenValueEg - RookValueEg - + PushToEdges[loserKSq] - + PushClose[distance(winnerKSq, loserKSq)]; + + push_to_edge(weakKing) + + push_close(strongKing, weakKing); + + return strongSide == pos.side_to_move() ? result : -result; +} + + +/// KNN vs KP. Very drawish, but there are some mate opportunities if we can +/// press the weakSide King to a corner before the pawn advances too much. +template<> +Value Endgame::operator()(const Position& pos) const { + + assert(verify_material(pos, strongSide, 2 * KnightValueMg, 0)); + assert(verify_material(pos, weakSide, VALUE_ZERO, 1)); + + Square weakKing = pos.square(weakSide); + Square weakPawn = pos.square(weakSide); + + Value result = PawnValueEg + + 2 * push_to_edge(weakKing) + - 10 * relative_rank(weakSide, weakPawn); return strongSide == pos.side_to_move() ? result : -result; } @@ -332,51 +324,47 @@ ScaleFactor Endgame::operator()(const Position& pos) const { // 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(strongSide, PAWN); - File pawnsFile = file_of(lsb(pawns)); + Bitboard strongPawns = pos.pieces(strongSide, PAWN); + Bitboard allPawns = pos.pieces(PAWN); + + Square strongBishop = pos.square(strongSide); + Square weakKing = pos.square(weakSide); + Square strongKing = pos.square(strongSide); - // All pawns are on a single rook file? - if ( (pawnsFile == FILE_A || pawnsFile == FILE_H) - && !(pawns & ~file_bb(pawnsFile))) + // All strongSide pawns are on a single rook file? + if (!(strongPawns & ~FileABB) || !(strongPawns & ~FileHBB)) { - Square bishopSq = pos.square(strongSide); - Square queeningSq = relative_square(strongSide, make_square(pawnsFile, RANK_8)); - Square kingSq = pos.square(weakSide); + Square queeningSquare = relative_square(strongSide, make_square(file_of(lsb(strongPawns)), RANK_8)); - if ( opposite_colors(queeningSq, bishopSq) - && distance(queeningSq, kingSq) <= 1) + if ( opposite_colors(queeningSquare, strongBishop) + && distance(queeningSquare, weakKing) <= 1) return SCALE_FACTOR_DRAW; } // 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)) + if ((!(allPawns & ~FileBBB) || !(allPawns & ~FileGBB)) && pos.non_pawn_material(weakSide) == 0 && pos.count(weakSide) >= 1) { - // Get weakSide pawn that is closest to the home rank - Square weakPawnSq = backmost_sq(weakSide, pos.pieces(weakSide, PAWN)); - - Square strongKingSq = pos.square(strongSide); - Square weakKingSq = pos.square(weakSide); - Square bishopSq = pos.square(strongSide); + // Get the least advanced weakSide pawn + Square weakPawn = frontmost_sq(strongSide, pos.pieces(weakSide, PAWN)); // 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)) + // the bishop cannot attack it or they only have one pawn left. + if ( relative_rank(strongSide, weakPawn) == RANK_7 + && (strongPawns & (weakPawn + pawn_push(weakSide))) + && (opposite_colors(strongBishop, weakPawn) || !more_than_one(strongPawns))) { - int strongKingDist = distance(weakPawnSq, strongKingSq); - int weakKingDist = distance(weakPawnSq, weakKingSq); + int strongKingDist = distance(weakPawn, strongKing); + int weakKingDist = distance(weakPawn, weakKing); // 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 // 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 + // problem such as 8/4k1p1/6P1/1K6/3B4/8/8/8 w). + if ( relative_rank(strongSide, weakKing) >= RANK_7 && weakKingDist <= 2 && weakKingDist <= strongKingDist) return SCALE_FACTOR_DRAW; @@ -396,15 +384,16 @@ ScaleFactor Endgame::operator()(const Position& pos) const { assert(pos.count(weakSide) == 1); assert(pos.count(weakSide) >= 1); - Square kingSq = pos.square(weakSide); - Square rsq = pos.square(weakSide); + Square strongKing = pos.square(strongSide); + Square weakKing = pos.square(weakSide); + Square weakRook = pos.square(weakSide); - if ( relative_rank(weakSide, kingSq) <= RANK_2 - && relative_rank(weakSide, pos.square(strongSide)) >= RANK_4 - && relative_rank(weakSide, rsq) == RANK_3 + if ( relative_rank(weakSide, weakKing) <= RANK_2 + && relative_rank(weakSide, strongKing) >= RANK_4 + && relative_rank(weakSide, weakRook) == RANK_3 && ( pos.pieces(weakSide, PAWN) - & pos.attacks_from(kingSq) - & pos.attacks_from(rsq, strongSide))) + & attacks_bb(weakKing) + & pawn_attacks_bb(strongSide, weakRook))) return SCALE_FACTOR_DRAW; return SCALE_FACTOR_NONE; @@ -424,89 +413,89 @@ ScaleFactor Endgame::operator()(const Position& pos) const { assert(verify_material(pos, weakSide, RookValueMg, 0)); // 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 = make_square(f, RANK_8); + Square strongKing = normalize(pos, strongSide, pos.square(strongSide)); + Square strongRook = normalize(pos, strongSide, pos.square(strongSide)); + Square strongPawn = normalize(pos, strongSide, pos.square(strongSide)); + Square weakKing = normalize(pos, strongSide, pos.square(weakSide)); + Square weakRook = normalize(pos, strongSide, pos.square(weakSide)); + + File pawnFile = file_of(strongPawn); + Rank pawnRank = rank_of(strongPawn); + Square queeningSquare = make_square(pawnFile, 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 - && distance(bksq, queeningSq) <= 1 - && wksq <= SQ_H5 - && (rank_of(brsq) == RANK_6 || (r <= RANK_3 && rank_of(wrsq) != RANK_6))) + if ( pawnRank <= RANK_5 + && distance(weakKing, queeningSquare) <= 1 + && strongKing <= SQ_H5 + && (rank_of(weakRook) == RANK_6 || (pawnRank <= RANK_3 && rank_of(strongRook) != RANK_6))) return SCALE_FACTOR_DRAW; // 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 - && distance(bksq, queeningSq) <= 1 - && rank_of(wksq) + tempo <= RANK_6 - && (rank_of(brsq) == RANK_1 || (!tempo && distance(brsq, wpsq) >= 3))) + if ( pawnRank == RANK_6 + && distance(weakKing, queeningSquare) <= 1 + && rank_of(strongKing) + tempo <= RANK_6 + && (rank_of(weakRook) == RANK_1 || (!tempo && distance(weakRook, strongPawn) >= 3))) return SCALE_FACTOR_DRAW; - if ( r >= RANK_6 - && bksq == queeningSq - && rank_of(brsq) == RANK_1 - && (!tempo || distance(wksq, wpsq) >= 2)) + if ( pawnRank >= RANK_6 + && weakKing == queeningSquare + && rank_of(weakRook) == RANK_1 + && (!tempo || distance(strongKing, strongPawn) >= 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 // and the black rook is behind the pawn. - if ( wpsq == SQ_A7 - && wrsq == SQ_A8 - && (bksq == SQ_H7 || bksq == SQ_G7) - && file_of(brsq) == FILE_A - && (rank_of(brsq) <= RANK_3 || file_of(wksq) >= FILE_D || rank_of(wksq) <= RANK_5)) + if ( strongPawn == SQ_A7 + && strongRook == SQ_A8 + && (weakKing == SQ_H7 || weakKing == SQ_G7) + && file_of(weakRook) == FILE_A + && (rank_of(weakRook) <= RANK_3 || file_of(strongKing) >= FILE_D || rank_of(strongKing) <= RANK_5)) return SCALE_FACTOR_DRAW; // 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 + NORTH - && distance(wksq, wpsq) - tempo >= 2 - && distance(wksq, brsq) - tempo >= 2) + if ( pawnRank <= RANK_5 + && weakKing == strongPawn + NORTH + && distance(strongKing, strongPawn) - tempo >= 2 + && distance(strongKing, weakRook) - tempo >= 2) return SCALE_FACTOR_DRAW; // Pawn on the 7th rank supported by the rook from behind usually wins if the // attacking king is closer to the queening square than the defending king, // and the defending king cannot gain tempi by threatening the attacking rook. - if ( r == RANK_7 - && f != FILE_A - && file_of(wrsq) == f - && wrsq != 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)); + if ( pawnRank == RANK_7 + && pawnFile != FILE_A + && file_of(strongRook) == pawnFile + && strongRook != queeningSquare + && (distance(strongKing, queeningSquare) < distance(weakKing, queeningSquare) - 2 + tempo) + && (distance(strongKing, queeningSquare) < distance(weakKing, strongRook) + tempo)) + return ScaleFactor(SCALE_FACTOR_MAX - 2 * distance(strongKing, queeningSquare)); // Similar to the above, but with the pawn further back - if ( f != FILE_A - && file_of(wrsq) == f - && wrsq < wpsq - && (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)))) + if ( pawnFile != FILE_A + && file_of(strongRook) == pawnFile + && strongRook < strongPawn + && (distance(strongKing, queeningSquare) < distance(weakKing, queeningSquare) - 2 + tempo) + && (distance(strongKing, strongPawn + NORTH) < distance(weakKing, strongPawn + NORTH) - 2 + tempo) + && ( distance(weakKing, strongRook) + tempo >= 3 + || ( distance(strongKing, queeningSquare) < distance(weakKing, strongRook) + tempo + && (distance(strongKing, strongPawn + NORTH) < distance(weakKing, strongPawn) + tempo)))) return ScaleFactor( SCALE_FACTOR_MAX - - 8 * distance(wpsq, queeningSq) - - 2 * distance(wksq, queeningSq)); + - 8 * distance(strongPawn, queeningSquare) + - 2 * distance(strongKing, queeningSquare)); // 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 (pawnRank <= RANK_4 && weakKing > strongPawn) { - if (file_of(bksq) == file_of(wpsq)) + if (file_of(weakKing) == file_of(strongPawn)) return ScaleFactor(10); - if ( distance(bksq, wpsq) == 1 - && distance(wksq, bksq) > 2) - return ScaleFactor(24 - 2 * distance(wksq, bksq)); + if ( distance(weakKing, strongPawn) == 1 + && distance(strongKing, weakKing) > 2) + return ScaleFactor(24 - 2 * distance(strongKing, weakKing)); } return SCALE_FACTOR_NONE; } @@ -520,10 +509,11 @@ ScaleFactor Endgame::operator()(const Position& pos) const { // Test for a rook pawn if (pos.pieces(PAWN) & (FileABB | FileHBB)) { - Square ksq = pos.square(weakSide); - Square bsq = pos.square(weakSide); - Square psq = pos.square(strongSide); - Rank rk = relative_rank(strongSide, psq); + Square weakKing = pos.square(weakSide); + Square weakBishop = pos.square(weakSide); + Square strongKing = pos.square(strongSide); + Square strongPawn = pos.square(strongSide); + Rank pawnRank = relative_rank(strongSide, strongPawn); Direction push = pawn_push(strongSide); // If the pawn is on the 5th rank and the pawn (currently) is on @@ -531,11 +521,11 @@ ScaleFactor Endgame::operator()(const Position& pos) const { // 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)) + if (pawnRank == RANK_5 && !opposite_colors(weakBishop, strongPawn)) { - int d = distance(psq + 3 * push, ksq); + int d = distance(strongPawn + 3 * push, weakKing); - if (d <= 2 && !(d == 0 && ksq == pos.square(strongSide) + 2 * push)) + if (d <= 2 && !(d == 0 && weakKing == strongKing + 2 * push)) return ScaleFactor(24); else return ScaleFactor(48); @@ -545,10 +535,10 @@ ScaleFactor Endgame::operator()(const Position& pos) const { // 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 - && distance(psq + 2 * push, ksq) <= 1 - && (PseudoAttacks[BISHOP][bsq] & (psq + push)) - && distance(bsq, psq) >= 2) + if ( pawnRank == RANK_6 + && distance(strongPawn + 2 * push, weakKing) <= 1 + && (attacks_bb(weakBishop) & (strongPawn + push)) + && distance(weakBishop, strongPawn) >= 2) return ScaleFactor(8); } @@ -563,28 +553,28 @@ ScaleFactor Endgame::operator()(const Position& pos) const { assert(verify_material(pos, strongSide, RookValueMg, 2)); assert(verify_material(pos, weakSide, RookValueMg, 1)); - Square wpsq1 = pos.squares(strongSide)[0]; - Square wpsq2 = pos.squares(strongSide)[1]; - Square bksq = pos.square(weakSide); + Square strongPawn1 = pos.squares(strongSide)[0]; + Square strongPawn2 = pos.squares(strongSide)[1]; + Square weakKing = pos.square(weakSide); // Does the stronger side have a passed pawn? - if (pos.pawn_passed(strongSide, wpsq1) || pos.pawn_passed(strongSide, wpsq2)) + if (pos.pawn_passed(strongSide, strongPawn1) || pos.pawn_passed(strongSide, strongPawn2)) return SCALE_FACTOR_NONE; - Rank r = std::max(relative_rank(strongSide, wpsq1), relative_rank(strongSide, wpsq2)); + Rank pawnRank = std::max(relative_rank(strongSide, strongPawn1), relative_rank(strongSide, strongPawn2)); - if ( distance(bksq, wpsq1) <= 1 - && distance(bksq, wpsq2) <= 1 - && relative_rank(strongSide, bksq) > r) + if ( distance(weakKing, strongPawn1) <= 1 + && distance(weakKing, strongPawn2) <= 1 + && relative_rank(strongSide, weakKing) > pawnRank) { - assert(r > RANK_1 && r < RANK_7); - return ScaleFactor(KRPPKRPScaleFactors[r]); + assert(pawnRank > RANK_1 && pawnRank < RANK_7); + return ScaleFactor(7 * pawnRank); } return SCALE_FACTOR_NONE; } -/// K and two or more pawns vs K. There is just a single rule here: If all pawns +/// K and two or more pawns vs K. There is just a single rule here: if all pawns /// are on the same rook file and are blocked by the defending king, it's a draw. template<> ScaleFactor Endgame::operator()(const Position& pos) const { @@ -593,14 +583,12 @@ ScaleFactor Endgame::operator()(const Position& pos) const { assert(pos.count(strongSide) >= 2); assert(verify_material(pos, weakSide, VALUE_ZERO, 0)); - Square ksq = pos.square(weakSide); - Bitboard pawns = pos.pieces(strongSide, PAWN); + Square weakKing = pos.square(weakSide); + Bitboard strongPawns = pos.pieces(strongSide, PAWN); - // 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) + // If all pawns are ahead of the king on a single rook file, it's a draw. + if ( !(strongPawns & ~(FileABB | FileHBB)) + && !(strongPawns & ~passed_pawn_span(weakSide, weakKing))) return SCALE_FACTOR_DRAW; return SCALE_FACTOR_NONE; @@ -617,20 +605,19 @@ ScaleFactor Endgame::operator()(const Position& pos) const { assert(verify_material(pos, strongSide, BishopValueMg, 1)); assert(verify_material(pos, weakSide, BishopValueMg, 0)); - Square pawnSq = pos.square(strongSide); - Square strongBishopSq = pos.square(strongSide); - Square weakBishopSq = pos.square(weakSide); - Square weakKingSq = pos.square(weakSide); + Square strongPawn = pos.square(strongSide); + Square strongBishop = pos.square(strongSide); + Square weakBishop = pos.square(weakSide); + Square weakKing = pos.square(weakSide); // Case 1: Defending king blocks the pawn, and cannot be driven away - 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)) + if ( (forward_file_bb(strongSide, strongPawn) & weakKing) + && ( opposite_colors(weakKing, strongBishop) + || relative_rank(strongSide, weakKing) <= RANK_6)) return SCALE_FACTOR_DRAW; // Case 2: Opposite colored bishops - if (opposite_colors(strongBishopSq, weakBishopSq)) + if (opposite_colors(strongBishop, weakBishop)) return SCALE_FACTOR_DRAW; return SCALE_FACTOR_NONE; @@ -644,38 +631,36 @@ ScaleFactor Endgame::operator()(const Position& pos) const { assert(verify_material(pos, strongSide, BishopValueMg, 2)); assert(verify_material(pos, weakSide, BishopValueMg, 0)); - Square wbsq = pos.square(strongSide); - Square bbsq = pos.square(weakSide); + Square strongBishop = pos.square(strongSide); + Square weakBishop = pos.square(weakSide); - if (!opposite_colors(wbsq, bbsq)) + if (!opposite_colors(strongBishop, weakBishop)) return SCALE_FACTOR_NONE; - 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 weakKing = pos.square(weakSide); + Square strongPawn1 = pos.squares(strongSide)[0]; + Square strongPawn2 = pos.squares(strongSide)[1]; Square blockSq1, blockSq2; - if (relative_rank(strongSide, psq1) > relative_rank(strongSide, psq2)) + if (relative_rank(strongSide, strongPawn1) > relative_rank(strongSide, strongPawn2)) { - blockSq1 = psq1 + pawn_push(strongSide); - blockSq2 = make_square(file_of(psq2), rank_of(psq1)); + blockSq1 = strongPawn1 + pawn_push(strongSide); + blockSq2 = make_square(file_of(strongPawn2), rank_of(strongPawn1)); } else { - blockSq1 = psq2 + pawn_push(strongSide); - blockSq2 = make_square(file_of(psq1), rank_of(psq2)); + blockSq1 = strongPawn2 + pawn_push(strongSide); + blockSq2 = make_square(file_of(strongPawn1), rank_of(strongPawn2)); } - switch (distance(psq1, psq2)) + switch (distance(strongPawn1, strongPawn2)) { case 0: // 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)) + if ( file_of(weakKing) == file_of(blockSq1) + && relative_rank(strongSide, weakKing) >= relative_rank(strongSide, blockSq1) + && opposite_colors(weakKing, strongBishop)) return SCALE_FACTOR_DRAW; else return SCALE_FACTOR_NONE; @@ -684,17 +669,17 @@ ScaleFactor Endgame::operator()(const Position& pos) const { // 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)) - || distance(r1, r2) >= 2)) + if ( weakKing == blockSq1 + && opposite_colors(weakKing, strongBishop) + && ( weakBishop == blockSq2 + || (attacks_bb(blockSq2, pos.pieces()) & pos.pieces(weakSide, BISHOP)) + || distance(strongPawn1, strongPawn2) >= 2)) return SCALE_FACTOR_DRAW; - else if ( ksq == blockSq2 - && opposite_colors(ksq, wbsq) - && ( bbsq == blockSq1 - || (pos.attacks_from(blockSq1) & pos.pieces(weakSide, BISHOP)))) + else if ( weakKing == blockSq2 + && opposite_colors(weakKing, strongBishop) + && ( weakBishop == blockSq1 + || (attacks_bb(blockSq1, pos.pieces()) & pos.pieces(weakSide, BISHOP)))) return SCALE_FACTOR_DRAW; else return SCALE_FACTOR_NONE; @@ -706,7 +691,7 @@ ScaleFactor Endgame::operator()(const Position& pos) const { } -/// KBP vs KN. There is a single rule: If the defending king is somewhere along +/// 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<> @@ -715,59 +700,22 @@ ScaleFactor Endgame::operator()(const Position& pos) const { assert(verify_material(pos, strongSide, BishopValueMg, 1)); assert(verify_material(pos, weakSide, KnightValueMg, 0)); - Square pawnSq = pos.square(strongSide); - Square strongBishopSq = pos.square(strongSide); - Square weakKingSq = pos.square(weakSide); + Square strongPawn = pos.square(strongSide); + Square strongBishop = pos.square(strongSide); + Square weakKing = pos.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)) + if ( file_of(weakKing) == file_of(strongPawn) + && relative_rank(strongSide, strongPawn) < relative_rank(strongSide, weakKing) + && ( opposite_colors(weakKing, strongBishop) + || relative_rank(strongSide, weakKing) <= RANK_6)) return SCALE_FACTOR_DRAW; return SCALE_FACTOR_NONE; } -/// 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)); - - // 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 == SQ_A7 && distance(SQ_A8, weakKingSq) <= 1) - return SCALE_FACTOR_DRAW; - - return SCALE_FACTOR_NONE; -} - - -/// 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.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_file_bb(strongSide, pawnSq) & pos.attacks_from(bishopSq)) - return ScaleFactor(distance(weakKingSq, pawnSq)); - - return SCALE_FACTOR_NONE; -} - - /// 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 +/// 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). @@ -778,18 +726,18 @@ ScaleFactor Endgame::operator()(const Position& pos) const { assert(verify_material(pos, weakSide, VALUE_ZERO, 1)); // 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)); + Square strongKing = normalize(pos, strongSide, pos.square(strongSide)); + Square weakKing = normalize(pos, strongSide, pos.square(weakSide)); + Square strongPawn = normalize(pos, strongSide, pos.square(strongSide)); 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(psq) >= RANK_5 && file_of(psq) != FILE_A) + if (rank_of(strongPawn) >= RANK_5 && file_of(strongPawn) != 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(wksq, psq, bksq, us) ? SCALE_FACTOR_NONE : SCALE_FACTOR_DRAW; + return Bitbases::probe(strongKing, strongPawn, weakKing, us) ? SCALE_FACTOR_NONE : SCALE_FACTOR_DRAW; }