X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fendgame.cpp;h=e1ff568f7716b4f306ff04f71ab8e30bed459608;hp=e3cd20076e4aa9b83dfa9aef62375c6e02a8853e;hb=3674f18b97bbf54bcec9b474d2204302a311e9da;hpb=53bbcb78d55c0341805b7666f9245737df97a63b diff --git a/src/endgame.cpp b/src/endgame.cpp index e3cd2007..e1ff568f 100644 --- a/src/endgame.cpp +++ b/src/endgame.cpp @@ -1,7 +1,7 @@ /* Stockfish, a UCI chess playing engine derived from Glaurung 2.1 Copyright (C) 2004-2008 Tord Romstad (Glaurung author) - Copyright (C) 2008-2010 Marco Costalba, Joona Kiiski, Tord Romstad + Copyright (C) 2008-2013 Marco Costalba, Joona Kiiski, Tord Romstad Stockfish is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by @@ -17,27 +17,21 @@ along with this program. If not, see . */ - -//// -//// Includes -//// - +#include #include -#include "bitbase.h" +#include "bitboard.h" #include "bitcount.h" #include "endgame.h" +#include "movegen.h" - -//// -//// Local definitions -//// +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 uint8_t MateTable[64] = { + 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, @@ -48,9 +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 uint8_t KBNKMateTable[64] = { + 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, @@ -61,50 +55,77 @@ 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 }; - // Penalty for big distance between king and knight for the defending king - // and knight in KR vs KN endgames. - const int KRKNKingKnightDistancePenalty[8] = { 0, 0, 4, 10, 20, 32, 48, 70 }; +#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 - // Bitbase for KP vs K - uint8_t KPKBitbase[24576]; + // 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) { - // Various inline functions for accessing the above arrays - inline Value mate_table(Square s) { - return Value(MateTable[s]); - } + assert(code.length() > 0 && code.length() < 8); + assert(code[0] == 'K'); - inline Value kbnk_mate_table(Square s) { - return Value(KBNKMateTable[s]); - } + string sides[] = { code.substr(code.find('K', 1)), // Weak + code.substr(0, code.find('K', 1)) }; // Strong - inline Value distance_bonus(int d) { - return Value(DistanceBonus[d]); - } + std::transform(sides[c].begin(), sides[c].end(), sides[c].begin(), tolower); - inline Value krkn_king_knight_distance_penalty(int d) { - return Value(KRKNKingKnightDistancePenalty[d]); + string fen = sides[0] + char('0' + int(8 - code.length())) + + sides[1] + "/8/8/8/8/8/8/8 w - - 0 10"; + + return Position(fen, false, NULL).material_key(); } - // Function for probing the KP vs K bitbase - int probe_kpk(Square wksq, Square wpsq, Square bksq, Color stm); + 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() { -//// -//// Functions -//// + for_each(m1.begin(), m1.end(), delete_endgame); + for_each(m2.begin(), m2.end(), delete_endgame); +} -/// init_bitbases() is called during program initialization, and simply loads -/// bitbases from disk into memory. At the moment, there is only the bitbase -/// for KP vs K, but we may decide to add other bitbases later. +template +void Endgames::add(const string& code) { -void init_bitbases() { - generate_kpk_bitbase(KPKBitbase); + map((Endgame*)0)[key(code, WHITE)] = new Endgame(WHITE); + map((Endgame*)0)[key(code, BLACK)] = new Endgame(BLACK); } @@ -113,101 +134,99 @@ void init_bitbases() { /// attacking side a bonus for driving the defending king towards the edge /// of the board, and for keeping the distance between the two kings small. template<> -Value EvaluationFunction::apply(const Position& pos) const { +Value Endgame::operator()(const Position& pos) const { - assert(pos.non_pawn_material(weakerSide) == Value(0)); - assert(pos.piece_count(weakerSide, PAWN) == Value(0)); + assert(verify_material(pos, weakSide, VALUE_ZERO, 0)); + assert(!pos.checkers()); // Eval is never called when in check - Square winnerKSq = pos.king_square(strongerSide); - Square loserKSq = pos.king_square(weakerSide); + // Stalemate detection with lone king + if (pos.side_to_move() == weakSide && !MoveList(pos).size()) + return VALUE_DRAW; + + Square winnerKSq = pos.king_square(strongSide); + Square loserKSq = pos.king_square(weakSide); - Value result = pos.non_pawn_material(strongerSide) - + pos.piece_count(strongerSide, PAWN) * PawnValueEndgame - + mate_table(loserKSq) - + distance_bonus(square_distance(winnerKSq, loserKSq)); + Value result = pos.non_pawn_material(strongSide) + + pos.count(strongSide) * PawnValueEg + + PushToEdges[loserKSq] + + PushClose[square_distance(winnerKSq, loserKSq)]; - if ( pos.piece_count(strongerSide, QUEEN) - || pos.piece_count(strongerSide, ROOK) - || pos.piece_count(strongerSide, BISHOP) > 1) - // TODO: check for two equal-colored bishops! + 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; } /// Mate with KBN vs K. This is similar to KX vs K, but we have to drive the /// defending king towards a corner square of the right color. template<> -Value EvaluationFunction::apply(const Position& pos) const { +Value Endgame::operator()(const Position& pos) const { - assert(pos.non_pawn_material(weakerSide) == Value(0)); - assert(pos.piece_count(weakerSide, PAWN) == Value(0)); - assert(pos.non_pawn_material(strongerSide) == KnightValueMidgame + BishopValueMidgame); - assert(pos.piece_count(strongerSide, BISHOP) == 1); - assert(pos.piece_count(strongerSide, KNIGHT) == 1); - assert(pos.piece_count(strongerSide, PAWN) == 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 bishopSquare = pos.piece_list(strongerSide, BISHOP, 0); + Square winnerKSq = pos.king_square(strongSide); + Square loserKSq = pos.king_square(weakSide); + Square bishopSq = pos.list(strongSide)[0]; - if (square_color(bishopSquare) == BLACK) + // kbnk_mate_table() tries to drive toward corners A1 or H8, + // if we have a bishop that cannot reach the above squares we + // flip the kings so to drive enemy toward corners A8 or H1. + if (opposite_colors(bishopSq, SQ_A1)) { - winnerKSq = flop_square(winnerKSq); - loserKSq = flop_square(loserKSq); + winnerKSq = ~winnerKSq; + loserKSq = ~loserKSq; } Value result = VALUE_KNOWN_WIN - + distance_bonus(square_distance(winnerKSq, loserKSq)) - + kbnk_mate_table(loserKSq); + + PushClose[square_distance(winnerKSq, loserKSq)] + + PushToCorners[loserKSq]; - return strongerSide == pos.side_to_move() ? result : -result; + return strongSide == pos.side_to_move() ? result : -result; } +// Returns a square that will allow us to orient the board so that +// strongSide is white and strongSide's only pawn is on the left +// half of the board +Square get_flip_sq(const Position& pos, Color strongSide) { + + assert(pos.count(strongSide) == 1); + + Square psq = pos.list(strongSide)[0]; + + return (FILE_H * (file_of(psq) >= FILE_E)) | (RANK_8 * int(strongSide)); +} + +Square operator^(Square s, Square flip_sq) { + assert(flip_sq == SQ_A1 || flip_sq == SQ_H1 || flip_sq == SQ_A8 || flip_sq == SQ_H8); + return Square(int(s) ^ int(flip_sq)); +} /// KP vs K. This endgame is evaluated with the help of a bitbase. template<> -Value EvaluationFunction::apply(const Position& pos) const { +Value Endgame::operator()(const Position& pos) const { - assert(pos.non_pawn_material(strongerSide) == Value(0)); - assert(pos.non_pawn_material(weakerSide) == Value(0)); - assert(pos.piece_count(strongerSide, PAWN) == 1); - assert(pos.piece_count(weakerSide, PAWN) == 0); + assert(verify_material(pos, strongSide, VALUE_ZERO, 1)); + assert(verify_material(pos, weakSide, VALUE_ZERO, 0)); - Square wksq, bksq, wpsq; - Color stm; + // Assume strongSide is white and the pawn is on files A-D + Square flip_sq = get_flip_sq(pos, strongSide); - if (strongerSide == WHITE) - { - wksq = pos.king_square(WHITE); - bksq = pos.king_square(BLACK); - wpsq = pos.piece_list(WHITE, PAWN, 0); - stm = pos.side_to_move(); - } - else - { - wksq = flip_square(pos.king_square(BLACK)); - bksq = flip_square(pos.king_square(WHITE)); - wpsq = flip_square(pos.piece_list(BLACK, PAWN, 0)); - stm = opposite_color(pos.side_to_move()); - } + Square wksq = pos.king_square(strongSide) ^ flip_sq; + Square bksq = pos.king_square(weakSide) ^ flip_sq; + Square psq = pos.list(strongSide)[0] ^ flip_sq; - if (square_file(wpsq) >= FILE_E) - { - wksq = flop_square(wksq); - bksq = flop_square(bksq); - wpsq = flop_square(wpsq); - } + Color us = strongSide == pos.side_to_move() ? WHITE : BLACK; - if (!probe_kpk(wksq, wpsq, bksq, stm)) + if (!Bitbases::probe_kpk(wksq, psq, bksq, us)) return VALUE_DRAW; - Value result = VALUE_KNOWN_WIN - + PawnValueEndgame - + Value(square_rank(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; } @@ -216,96 +235,96 @@ Value EvaluationFunction::apply(const Position& pos) const { /// far advanced with support of the king, while the attacking king is far /// away. template<> -Value EvaluationFunction::apply(const Position& pos) const { - - assert(pos.non_pawn_material(strongerSide) == RookValueMidgame); - assert(pos.piece_count(strongerSide, PAWN) == 0); - assert(pos.non_pawn_material(weakerSide) == 0); - assert(pos.piece_count(weakerSide, PAWN) == 1); +Value Endgame::operator()(const Position& pos) const { - 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); - wrsq = pos.piece_list(strongerSide, ROOK, 0); - bksq = pos.king_square(weakerSide); - bpsq = pos.piece_list(weakerSide, PAWN, 0); - - if (strongerSide == BLACK) - { - wksq = flip_square(wksq); - wrsq = flip_square(wrsq); - bksq = flip_square(bksq); - bpsq = flip_square(bpsq); - } + Square wksq = relative_square(strongSide, pos.king_square(strongSide)); + Square bksq = relative_square(strongSide, pos.king_square(weakSide)); + Square rsq = relative_square(strongSide, pos.list(strongSide)[0]); + Square psq = relative_square(strongSide, pos.list(weakSide)[0]); - Square queeningSq = make_square(square_file(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 && square_file(wksq) == square_file(bpsq)) - result = RookValueEndgame - 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 = RookValueEndgame - 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 ( square_rank(bksq) <= RANK_3 - && square_distance(bksq, bpsq) == 1 - && square_rank(wksq) >= RANK_4 - && square_distance(wksq, bpsq) - tempo > 2) - result = Value(80 - square_distance(wksq, bpsq) * 8); + else if ( rank_of(bksq) <= RANK_3 + && square_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); 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; } /// KR vs KB. This is very simple, and always returns drawish scores. The /// score is slightly bigger when the defending king is close to the edge. template<> -Value EvaluationFunction::apply(const Position& pos) const { +Value Endgame::operator()(const Position& pos) const { - assert(pos.non_pawn_material(strongerSide) == RookValueMidgame); - assert(pos.piece_count(strongerSide, PAWN) == 0); - assert(pos.non_pawn_material(weakerSide) == BishopValueMidgame); - assert(pos.piece_count(weakerSide, PAWN) == 0); - assert(pos.piece_count(weakerSide, BISHOP) == 1); + assert(verify_material(pos, strongSide, RookValueMg, 0)); + assert(verify_material(pos, weakSide, BishopValueMg, 0)); - Value result = mate_table(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; } /// KR vs KN. The attacking side has slightly better winning chances than /// in KR vs KB, particularly if the king and the knight are far apart. template<> -Value EvaluationFunction::apply(const Position& pos) const { +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)]); + 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. +template<> +Value Endgame::operator()(const Position& pos) const { - assert(pos.non_pawn_material(strongerSide) == RookValueMidgame); - assert(pos.piece_count(strongerSide, PAWN) == 0); - assert(pos.non_pawn_material(weakerSide) == KnightValueMidgame); - assert(pos.piece_count(weakerSide, PAWN) == 0); - assert(pos.piece_count(weakerSide, KNIGHT) == 1); + assert(verify_material(pos, strongSide, QueenValueMg, 0)); + assert(verify_material(pos, weakSide, VALUE_ZERO, 1)); - Square defendingKSq = pos.king_square(weakerSide); - Square nSq = pos.piece_list(weakerSide, KNIGHT, 0); + Square winnerKSq = pos.king_square(strongSide); + Square loserKSq = pos.king_square(weakSide); + Square pawnSq = pos.list(weakSide)[0]; - int d = square_distance(defendingKSq, nSq); - Value result = Value(10) - + mate_table(defendingKSq) - + krkn_king_knight_distance_penalty(d); + Value result = Value(PushClose[square_distance(winnerKSq, loserKSq)]); - return strongerSide == pos.side_to_move() ? result : -result; + if ( relative_rank(weakSide, pawnSq) != RANK_7 + || square_distance(loserKSq, pawnSq) != 1 + || !((FileABB | FileCBB | FileFBB | FileHBB) & pawnSq)) + result += QueenValueEg - PawnValueEg; + + return strongSide == pos.side_to_move() ? result : -result; } @@ -315,221 +334,199 @@ Value EvaluationFunction::apply(const Position& pos) const { /// for the defending side in the search, this is usually sufficient to be /// able to win KQ vs KR. template<> -Value EvaluationFunction::apply(const Position& pos) const { +Value Endgame::operator()(const Position& pos) const { - assert(pos.non_pawn_material(strongerSide) == QueenValueMidgame); - assert(pos.piece_count(strongerSide, PAWN) == 0); - assert(pos.non_pawn_material(weakerSide) == RookValueMidgame); - assert(pos.piece_count(weakerSide, PAWN) == 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 = QueenValueEndgame - - RookValueEndgame - + mate_table(loserKSq) - + distance_bonus(square_distance(winnerKSq, loserKSq)); + Value result = QueenValueEg + - RookValueEg + + 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 EvaluationFunction::apply(const Position& pos) const { - assert(pos.piece_count(strongerSide, BISHOP) == 2); - assert(pos.non_pawn_material(strongerSide) == 2*BishopValueMidgame); - assert(pos.piece_count(weakerSide, KNIGHT) == 1); - assert(pos.non_pawn_material(weakerSide) == KnightValueMidgame); - assert(pos.pieces(PAWN) == EmptyBoardBB); +/// 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 = BishopValueEndgame; - Square wksq = pos.king_square(strongerSide); - Square bksq = pos.king_square(weakerSide); - Square nsq = pos.piece_list(weakerSide, KNIGHT, 0); +template<> +Value Endgame::operator()(const Position& pos) const { - // Bonus for attacking king close to defending king - result += distance_bonus(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 - count_1s_max_15(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 EvaluationFunction::apply(const Position&) const { - return Value(0); -} +/// 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 EvaluationFunction::apply(const Position&) const { - return Value(0); -} -/// KBPKScalingFunction scales endgames where the stronger side has king, -/// bishop and one or more pawns. It checks for draws with rook pawns and a -/// bishop of the wrong color. If such a draw is detected, SCALE_FACTOR_ZERO is -/// returned. If not, the return value is SCALE_FACTOR_NONE, i.e. no scaling +/// 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 +/// is returned. If not, the return value is SCALE_FACTOR_NONE, i.e. no scaling /// will be used. template<> -ScaleFactor ScalingFunction::apply(const Position& pos) const { +ScaleFactor Endgame::operator()(const Position& pos) const { - assert(pos.non_pawn_material(strongerSide) == BishopValueMidgame); - assert(pos.piece_count(strongerSide, BISHOP) == 1); - assert(pos.piece_count(strongerSide, PAWN) >= 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(PAWN, strongerSide); - File pawnFile = square_file(pos.piece_list(strongerSide, PAWN, 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)) == EmptyBoardBB) + if ( (pawnFile == FILE_A || pawnFile == FILE_H) + && !(pawns & ~file_bb(pawnFile))) { - Square bishopSq = pos.piece_list(strongerSide, BISHOP, 0); - Square queeningSq = relative_square(strongerSide, make_square(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) + && square_distance(queeningSq, kingSq) <= 1) + return SCALE_FACTOR_DRAW; + } - if ( square_color(queeningSq) != square_color(bishopSq) - && file_distance(square_file(kingSq), pawnFile) <= 1) + // 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(weakSide) == 0 + && pos.count(weakSide) >= 1) + { + // 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)) { - // The bishop has the wrong color, and the defending king is on the - // file of the pawn(s) or the neighboring file. Find the rank of the - // frontmost pawn. - Rank rank; - if (strongerSide == WHITE) - { - for (rank = RANK_7; (rank_bb(rank) & pawns) == EmptyBoardBB; rank--) {} - assert(rank >= RANK_2 && rank <= RANK_7); - } - else - { - for (rank = RANK_2; (rank_bb(rank) & pawns) == EmptyBoardBB; rank++) {} - rank = Rank(rank ^ 7); // HACK to get the relative rank - assert(rank >= RANK_2 && rank <= RANK_7); - } - // If the defending king has distance 1 to the promotion square or - // is placed somewhere in front of the pawn, it's a draw. - if ( square_distance(kingSq, queeningSq) <= 1 - || relative_rank(strongerSide, kingSq) >= rank) - return SCALE_FACTOR_ZERO; + 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; } -/// KQKRPScalingFunction scales endgames where the stronger side has only -/// king and queen, while the weaker side has at least a rook and a pawn. -/// It tests for fortress draws with a rook on the third rank defended by -/// a pawn. +/// 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. template<> -ScaleFactor ScalingFunction::apply(const Position& pos) const { - - assert(pos.non_pawn_material(strongerSide) == QueenValueMidgame); - assert(pos.piece_count(strongerSide, QUEEN) == 1); - assert(pos.piece_count(strongerSide, PAWN) == 0); - assert(pos.piece_count(weakerSide, ROOK) == 1); - assert(pos.piece_count(weakerSide, PAWN) >= 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(ROOK, weakerSide) & relative_rank_bb(weakerSide, RANK_3)) - && (pos.pieces(PAWN, weakerSide) & relative_rank_bb(weakerSide, RANK_2)) - && (pos.attacks_from(kingSq) & pos.pieces(PAWN, weakerSide))) - { - Square rsq = pos.piece_list(weakerSide, ROOK, 0); - if (pos.attacks_from(rsq, strongerSide) & pos.pieces(PAWN, weakerSide)) - return SCALE_FACTOR_ZERO; - } +ScaleFactor Endgame::operator()(const Position& pos) const { + + 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; } -/// KRPKRScalingFunction scales KRP vs KR endgames. 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. +/// 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. /// /// It would also be nice to rewrite the actual code for this function, /// which is mostly copied from Glaurung 1.x, and not very pretty. template<> -ScaleFactor ScalingFunction::apply(const Position& pos) const { - - assert(pos.non_pawn_material(strongerSide) == RookValueMidgame); - assert(pos.piece_count(strongerSide, PAWN) == 1); - assert(pos.non_pawn_material(weakerSide) == RookValueMidgame); - assert(pos.piece_count(weakerSide, PAWN) == 0); - - Square wksq = pos.king_square(strongerSide); - Square wrsq = pos.piece_list(strongerSide, ROOK, 0); - Square wpsq = pos.piece_list(strongerSide, PAWN, 0); - Square bksq = pos.king_square(weakerSide); - Square brsq = pos.piece_list(weakerSide, ROOK, 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 = flip_square(wksq); - wrsq = flip_square(wrsq); - wpsq = flip_square(wpsq); - bksq = flip_square(bksq); - brsq = flip_square(brsq); - } - if (square_file(wpsq) > FILE_D) - { - wksq = flop_square(wksq); - wrsq = flop_square(wrsq); - wpsq = flop_square(wpsq); - bksq = flop_square(bksq); - brsq = flop_square(brsq); - } +ScaleFactor Endgame::operator()(const Position& pos) const { + + assert(verify_material(pos, strongSide, RookValueMg, 1)); + assert(verify_material(pos, weakSide, RookValueMg, 0)); - File f = square_file(wpsq); - Rank r = square_rank(wpsq); - Square queeningSq = make_square(f, RANK_8); - int tempo = (pos.side_to_move() == strongerSide); + // Assume strongSide is white and the pawn is on files A-D + Square flip_sq = get_flip_sq(pos, strongSide); + + Square wksq = pos.king_square(strongSide) ^ flip_sq; + Square bksq = pos.king_square(weakSide) ^ flip_sq; + Square wrsq = pos.list(strongSide)[0] ^ flip_sq; + Square wpsq = pos.list(strongSide)[0] ^ flip_sq; + Square brsq = pos.list(weakSide)[0] ^ flip_sq; + + File f = file_of(wpsq); + Rank r = rank_of(wpsq); + Square queeningSq = 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 && wksq <= SQ_H5 - && (square_rank(brsq) == RANK_6 || (r <= RANK_3 && square_rank(wrsq) != RANK_6))) - return SCALE_FACTOR_ZERO; + && (rank_of(brsq) == RANK_6 || (r <= RANK_3 && rank_of(wrsq) != 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 && square_distance(bksq, queeningSq) <= 1 - && square_rank(wksq) + tempo <= RANK_6 - && (square_rank(brsq) == RANK_1 || (!tempo && abs(square_file(brsq) - f) >= 3))) - return SCALE_FACTOR_ZERO; + && rank_of(wksq) + tempo <= RANK_6 + && (rank_of(brsq) == RANK_1 || (!tempo && abs(file_of(brsq) - f) >= 3))) + return SCALE_FACTOR_DRAW; if ( r >= RANK_6 && bksq == queeningSq - && square_rank(brsq) == RANK_1 + && rank_of(brsq) == RANK_1 && (!tempo || square_distance(wksq, wpsq) >= 2)) - return SCALE_FACTOR_ZERO; + 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) - && square_file(brsq) == FILE_A - && (square_rank(brsq) <= RANK_3 || square_file(wksq) >= FILE_D || square_rank(wksq) <= RANK_5)) - return SCALE_FACTOR_ZERO; + && file_of(brsq) == FILE_A + && (rank_of(brsq) <= RANK_3 || file_of(wksq) >= FILE_D || rank_of(wksq) <= 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. @@ -537,14 +534,14 @@ ScaleFactor ScalingFunction::apply(const Position& pos) const { && bksq == wpsq + DELTA_N && square_distance(wksq, wpsq) - tempo >= 2 && square_distance(wksq, brsq) - tempo >= 2) - return SCALE_FACTOR_ZERO; + 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 - && square_file(wrsq) == f + && 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)) @@ -552,7 +549,7 @@ ScaleFactor ScalingFunction::apply(const Position& pos) const { // Similar to the above, but with the pawn further back if ( f != FILE_A - && square_file(wrsq) == f + && 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) @@ -567,41 +564,81 @@ ScaleFactor ScalingFunction::apply(const Position& pos) const { // the pawn's path, it's probably a draw. if (r <= RANK_4 && bksq > wpsq) { - if (square_file(bksq) == square_file(wpsq)) + if (file_of(bksq) == file_of(wpsq)) return ScaleFactor(10); - if ( abs(square_file(bksq) - square_file(wpsq)) == 1 + if ( abs(file_of(bksq) - file_of(wpsq)) == 1 && square_distance(wksq, bksq) > 2) return ScaleFactor(24 - 2 * square_distance(wksq, bksq)); } return SCALE_FACTOR_NONE; } +template<> +ScaleFactor Endgame::operator()(const Position& pos) const { -/// KRPPKRPScalingFunction scales KRPP vs KRP endgames. There is only a -/// single pattern: If the stronger side has no pawns and the defending king + 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 /// is actively placed, the position is drawish. template<> -ScaleFactor ScalingFunction::apply(const Position& pos) const { +ScaleFactor Endgame::operator()(const Position& pos) const { - assert(pos.non_pawn_material(strongerSide) == RookValueMidgame); - assert(pos.piece_count(strongerSide, PAWN) == 2); - assert(pos.non_pawn_material(weakerSide) == RookValueMidgame); - assert(pos.piece_count(weakerSide, PAWN) == 1); + assert(verify_material(pos, strongSide, RookValueMg, 2)); + assert(verify_material(pos, weakSide, RookValueMg, 1)); - Square wpsq1 = pos.piece_list(strongerSide, PAWN, 0); - Square wpsq2 = pos.piece_list(strongerSide, PAWN, 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 = 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); @@ -616,71 +653,54 @@ ScaleFactor ScalingFunction::apply(const Position& pos) const { } -/// KPsKScalingFunction scales endgames with king and two or more pawns -/// against king. There is just a single rule here: If all pawns are on -/// the same rook file and are blocked by the defending king, it's a draw. +/// 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 ScalingFunction::apply(const Position& pos) const { +ScaleFactor Endgame::operator()(const Position& pos) const { - assert(pos.non_pawn_material(strongerSide) == Value(0)); - assert(pos.piece_count(strongerSide, PAWN) >= 2); - assert(pos.non_pawn_material(weakerSide) == Value(0)); - assert(pos.piece_count(weakerSide, PAWN) == 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(PAWN, strongerSide); + 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) == EmptyBoardBB) - { - // Does the defending king block the pawns? - if ( square_distance(ksq, relative_square(strongerSide, SQ_A8)) <= 1 - || ( square_file(ksq) == FILE_A - && (in_front_bb(strongerSide, ksq) & pawns) == EmptyBoardBB)) - return SCALE_FACTOR_ZERO; - } - // Are all pawns on the 'h' file? - else if ((pawns & ~FileHBB) == EmptyBoardBB) - { - // Does the defending king block the pawns? - if ( square_distance(ksq, relative_square(strongerSide, SQ_H8)) <= 1 - || ( square_file(ksq) == FILE_H - && (in_front_bb(strongerSide, ksq) & pawns) == EmptyBoardBB)) - return SCALE_FACTOR_ZERO; - } return SCALE_FACTOR_NONE; } -/// KBPKBScalingFunction scales KBP vs KB endgames. 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. +/// 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. template<> -ScaleFactor ScalingFunction::apply(const Position& pos) const { +ScaleFactor Endgame::operator()(const Position& pos) const { - assert(pos.non_pawn_material(strongerSide) == BishopValueMidgame); - assert(pos.piece_count(strongerSide, BISHOP) == 1); - assert(pos.piece_count(strongerSide, PAWN) == 1); - assert(pos.non_pawn_material(weakerSide) == BishopValueMidgame); - assert(pos.piece_count(weakerSide, BISHOP) == 1); - assert(pos.piece_count(weakerSide, PAWN) == 0); + assert(verify_material(pos, strongSide, BishopValueMg, 1)); + assert(verify_material(pos, weakSide, BishopValueMg, 0)); - Square pawnSq = pos.piece_list(strongerSide, PAWN, 0); - Square strongerBishopSq = pos.piece_list(strongerSide, BISHOP, 0); - Square weakerBishopSq = pos.piece_list(weakerSide, BISHOP, 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 ( square_file(weakerKingSq) == square_file(pawnSq) - && relative_rank(strongerSide, pawnSq) < relative_rank(strongerSide, weakerKingSq) - && ( square_color(weakerKingSq) != square_color(strongerBishopSq) - || relative_rank(strongerSide, weakerKingSq) <= RANK_6)) - return SCALE_FACTOR_ZERO; + 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 (square_color(strongerBishopSq) != square_color(weakerBishopSq)) + if (opposite_colors(strongBishopSq, weakBishopSq)) { // We assume that the position is drawn in the following three situations: // @@ -692,58 +712,54 @@ ScaleFactor ScalingFunction::apply(const Position& pos) const { // These rules are probably not perfect, but in practice they work // reasonably well. - if (relative_rank(strongerSide, pawnSq) <= RANK_5) - return SCALE_FACTOR_ZERO; + if (relative_rank(strongSide, pawnSq) <= RANK_5) + return SCALE_FACTOR_DRAW; else { - Bitboard ray = ray_bb(pawnSq, (strongerSide == WHITE)? SIGNED_DIR_N : SIGNED_DIR_S); - if (ray & pos.pieces(KING, weakerSide)) - return SCALE_FACTOR_ZERO; + Bitboard path = forward_bb(strongSide, pawnSq); - if ( (pos.attacks_from(weakerBishopSq) & ray) - && square_distance(weakerBishopSq, pawnSq) >= 3) - return SCALE_FACTOR_ZERO; + if (path & pos.pieces(weakSide, KING)) + return SCALE_FACTOR_DRAW; + + if ( (pos.attacks_from(weakBishopSq) & path) + && square_distance(weakBishopSq, pawnSq) >= 3) + return SCALE_FACTOR_DRAW; } } return SCALE_FACTOR_NONE; } -/// KBPPKBScalingFunction scales KBPP vs KB endgames. It detects a few basic -/// draws with opposite-colored bishops. +/// K, bishop and two pawns vs K and bishop. It detects a few basic draws with +/// opposite-colored bishops. template<> -ScaleFactor ScalingFunction::apply(const Position& pos) const { +ScaleFactor Endgame::operator()(const Position& pos) const { - assert(pos.non_pawn_material(strongerSide) == BishopValueMidgame); - assert(pos.piece_count(strongerSide, BISHOP) == 1); - assert(pos.piece_count(strongerSide, PAWN) == 2); - assert(pos.non_pawn_material(weakerSide) == BishopValueMidgame); - assert(pos.piece_count(weakerSide, BISHOP) == 1); - assert(pos.piece_count(weakerSide, PAWN) == 0); + assert(verify_material(pos, strongSide, BishopValueMg, 2)); + assert(verify_material(pos, weakSide, BishopValueMg, 0)); - Square wbsq = pos.piece_list(strongerSide, BISHOP, 0); - Square bbsq = pos.piece_list(weakerSide, BISHOP, 0); + Square wbsq = pos.list(strongSide)[0]; + Square bbsq = pos.list(weakSide)[0]; - if (square_color(wbsq) == square_color(bbsq)) - // Not opposite-colored bishops, no scaling + if (!opposite_colors(wbsq, bbsq)) return SCALE_FACTOR_NONE; - Square ksq = pos.king_square(weakerSide); - Square psq1 = pos.piece_list(strongerSide, PAWN, 0); - Square psq2 = pos.piece_list(strongerSide, PAWN, 1); - Rank r1 = square_rank(psq1); - Rank r2 = square_rank(psq2); + 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); - blockSq2 = make_square(square_file(psq2), square_rank(psq1)); + blockSq1 = psq1 + pawn_push(strongSide); + blockSq2 = file_of(psq2) | rank_of(psq1); } else { - blockSq1 = psq2 + pawn_push(strongerSide); - blockSq2 = make_square(square_file(psq1), square_rank(psq2)); + blockSq1 = psq2 + pawn_push(strongSide); + blockSq2 = file_of(psq1) | rank_of(psq2); } switch (file_distance(psq1, psq2)) @@ -751,29 +767,29 @@ ScaleFactor ScalingFunction::apply(const Position& pos) const { case 0: // Both pawns are on the same file. Easy draw if defender firmly controls // some square in the frontmost pawn's path. - if ( square_file(ksq) == square_file(blockSq1) - && relative_rank(strongerSide, ksq) >= relative_rank(strongerSide, blockSq1) - && square_color(ksq) != square_color(wbsq)) - return SCALE_FACTOR_ZERO; + if ( file_of(ksq) == file_of(blockSq1) + && relative_rank(strongSide, ksq) >= relative_rank(strongSide, blockSq1) + && opposite_colors(ksq, wbsq)) + return SCALE_FACTOR_DRAW; else return SCALE_FACTOR_NONE; case 1: - // Pawns on neighboring files. Draw if defender firmly controls the square + // 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. if ( ksq == blockSq1 - && square_color(ksq) != square_color(wbsq) + && opposite_colors(ksq, wbsq) && ( bbsq == blockSq2 - || (pos.attacks_from(blockSq2) & pos.pieces(BISHOP, weakerSide)) - || rank_distance(r1, r2) >= 2)) - return SCALE_FACTOR_ZERO; + || (pos.attacks_from(blockSq2) & pos.pieces(weakSide, BISHOP)) + || abs(r1 - r2) >= 2)) + return SCALE_FACTOR_DRAW; else if ( ksq == blockSq2 - && square_color(ksq) != square_color(wbsq) + && opposite_colors(ksq, wbsq) && ( bbsq == blockSq1 - || (pos.attacks_from(blockSq1) & pos.pieces(BISHOP, weakerSide)))) - return SCALE_FACTOR_ZERO; + || (pos.attacks_from(blockSq1) & pos.pieces(weakSide, BISHOP)))) + return SCALE_FACTOR_DRAW; else return SCALE_FACTOR_NONE; @@ -784,123 +800,95 @@ ScaleFactor ScalingFunction::apply(const Position& pos) const { } -/// KBPKNScalingFunction scales KBP vs KN endgames. 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. +/// 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. template<> -ScaleFactor ScalingFunction::apply(const Position& pos) const { +ScaleFactor Endgame::operator()(const Position& pos) const { - assert(pos.non_pawn_material(strongerSide) == BishopValueMidgame); - assert(pos.piece_count(strongerSide, BISHOP) == 1); - assert(pos.piece_count(strongerSide, PAWN) == 1); - assert(pos.non_pawn_material(weakerSide) == KnightValueMidgame); - assert(pos.piece_count(weakerSide, KNIGHT) == 1); - assert(pos.piece_count(weakerSide, PAWN) == 0); + assert(verify_material(pos, strongSide, BishopValueMg, 1)); + assert(verify_material(pos, weakSide, KnightValueMg, 0)); - Square pawnSq = pos.piece_list(strongerSide, PAWN, 0); - Square strongerBishopSq = pos.piece_list(strongerSide, BISHOP, 0); - Square weakerKingSq = pos.king_square(weakerSide); + Square pawnSq = pos.list(strongSide)[0]; + Square strongBishopSq = pos.list(strongSide)[0]; + Square weakKingSq = pos.king_square(weakSide); - if ( square_file(weakerKingSq) == square_file(pawnSq) - && relative_rank(strongerSide, pawnSq) < relative_rank(strongerSide, weakerKingSq) - && ( square_color(weakerKingSq) != square_color(strongerBishopSq) - || relative_rank(strongerSide, weakerKingSq) <= RANK_6)) - return SCALE_FACTOR_ZERO; + 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; } -/// KNPKScalingFunction scales KNP vs K endgames. 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. +/// 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. template<> -ScaleFactor ScalingFunction::apply(const Position& pos) const { +ScaleFactor Endgame::operator()(const Position& pos) const { - assert(pos.non_pawn_material(strongerSide) == KnightValueMidgame); - assert(pos.piece_count(strongerSide, KNIGHT) == 1); - assert(pos.piece_count(strongerSide, PAWN) == 1); - assert(pos.non_pawn_material(weakerSide) == Value(0)); - assert(pos.piece_count(weakerSide, PAWN) == 0); + assert(verify_material(pos, strongSide, KnightValueMg, 1)); + assert(verify_material(pos, weakSide, VALUE_ZERO, 0)); - Square pawnSq = pos.piece_list(strongerSide, PAWN, 0); - Square weakerKingSq = pos.king_square(weakerSide); + // Assume strongSide is white and the pawn is on files A-D + Square flip_sq = get_flip_sq(pos, strongSide); - if ( pawnSq == relative_square(strongerSide, SQ_A7) - && square_distance(weakerKingSq, relative_square(strongerSide, SQ_A8)) <= 1) - return SCALE_FACTOR_ZERO; + Square pawnSq = pos.list(strongSide)[0] ^ flip_sq; + Square weakKingSq = pos.king_square(weakSide) ^ flip_sq; - if ( pawnSq == relative_square(strongerSide, SQ_H7) - && square_distance(weakerKingSq, relative_square(strongerSide, SQ_H8)) <= 1) - return SCALE_FACTOR_ZERO; + if (pawnSq == SQ_A7 && square_distance(SQ_A8, weakKingSq) <= 1) + return SCALE_FACTOR_DRAW; return SCALE_FACTOR_NONE; } -/// KPKPScalingFunction scales KP vs KP endgames. 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). +/// K, knight and a pawn vs K and bishop. If knight can block bishop from taking +/// pawn, it's a win. Otherwise, drawn. template<> -ScaleFactor ScalingFunction::apply(const Position& pos) const { - - assert(pos.non_pawn_material(strongerSide) == Value(0)); - assert(pos.non_pawn_material(weakerSide) == Value(0)); - assert(pos.piece_count(WHITE, PAWN) == 1); - assert(pos.piece_count(BLACK, PAWN) == 1); - - Square wksq, bksq, wpsq; - Color stm; - - if (strongerSide == WHITE) - { - wksq = pos.king_square(WHITE); - bksq = pos.king_square(BLACK); - wpsq = pos.piece_list(WHITE, PAWN, 0); - stm = pos.side_to_move(); - } - else - { - wksq = flip_square(pos.king_square(BLACK)); - bksq = flip_square(pos.king_square(WHITE)); - wpsq = flip_square(pos.piece_list(BLACK, PAWN, 0)); - stm = opposite_color(pos.side_to_move()); - } +ScaleFactor Endgame::operator()(const Position& pos) const { - if (square_file(wpsq) >= FILE_E) - { - wksq = flop_square(wksq); - bksq = flop_square(bksq); - wpsq = flop_square(wpsq); - } + Square pawnSq = pos.list(strongSide)[0]; + Square bishopSq = pos.list(weakSide)[0]; + Square weakKingSq = pos.king_square(weakSide); - // 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 ( square_rank(wpsq) >= RANK_5 - && square_file(wpsq) != FILE_A) - return SCALE_FACTOR_NONE; + // 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)); - // 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 probe_kpk(wksq, wpsq, bksq, stm) ? SCALE_FACTOR_NONE : SCALE_FACTOR_ZERO; + return SCALE_FACTOR_NONE; } -namespace { +/// 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). +template<> +ScaleFactor Endgame::operator()(const Position& pos) const { - // Probe the KP vs K bitbase + assert(verify_material(pos, strongSide, VALUE_ZERO, 1)); + assert(verify_material(pos, weakSide, VALUE_ZERO, 1)); - int probe_kpk(Square wksq, Square wpsq, Square bksq, Color stm) { + // Assume strongSide is white and the pawn is on files A-D + Square flip_sq = get_flip_sq(pos, strongSide); - int wp = square_file(wpsq) + 4 * (square_rank(wpsq) - 1); - int index = int(stm) + 2 * bksq + 128 * wksq + 8192 * wp; + Square wksq = pos.king_square(strongSide) ^ flip_sq; + Square bksq = pos.king_square(weakSide) ^ flip_sq; + Square psq = pos.list(strongSide)[0] ^ flip_sq; - assert(index >= 0 && index < 24576 * 8); + Color us = strongSide == pos.side_to_move() ? WHITE : BLACK; - return KPKBitbase[index / 8] & (1 << (index & 7)); - } + // 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) + 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, psq, bksq, us) ? SCALE_FACTOR_NONE : SCALE_FACTOR_DRAW; }