+++ /dev/null
-/*
- Stockfish, a UCI chess playing engine derived from Glaurung 2.1
- Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
- Copyright (C) 2008-2012 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
- the Free Software Foundation, either version 3 of the License, or
- (at your option) any later version.
-
- Stockfish is distributed in the hope that it will be useful,
- but WITHOUT ANY WARRANTY; without even the implied warranty of
- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- GNU General Public License for more details.
-
- You should have received a copy of the GNU General Public License
- along with this program. If not, see <http://www.gnu.org/licenses/>.
-*/
-
-#include <algorithm>
-#include <cassert>
-
-#include "bitboard.h"
-#include "bitcount.h"
-#include "endgame.h"
-#include "movegen.h"
-
-using std::string;
-
-namespace {
-
- // Table used to drive the defending king towards the edge of the board
- // in KX vs K and KQ vs KR endgames.
- const int MateTable[64] = {
- 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 defending king towards a corner square of the
- // right color in KBN vs K endgames.
- const int KBNKMateTable[64] = {
- 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
- };
-
- // 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 };
-
- // Get the material key of a Position out of the given endgame key code
- // like "KBPKN". The trick here is to first forge an ad-hoc fen string
- // and then let a Position object to do the work for us. Note that the
- // fen string could correspond to an illegal position.
- Key key(const string& code, Color c) {
-
- assert(code.length() > 0 && code.length() < 8);
- assert(code[0] == 'K');
-
- string sides[] = { code.substr(code.find('K', 1)), // Weaker
- code.substr(0, code.find('K', 1)) }; // Stronger
-
- std::transform(sides[c].begin(), sides[c].end(), sides[c].begin(), tolower);
-
- string fen = sides[0] + char('0' + int(8 - code.length()))
- + sides[1] + "/8/8/8/8/8/8/8 w - - 0 10";
-
- return Position(fen, false, NULL).material_key();
- }
-
- template<typename M>
- void delete_endgame(const typename M::value_type& p) { delete p.second; }
-
-} // namespace
-
-
-/// Endgames members definitions
-
-Endgames::Endgames() {
-
- add<KPK>("KPK");
- add<KNNK>("KNNK");
- add<KBNK>("KBNK");
- add<KRKP>("KRKP");
- add<KRKB>("KRKB");
- add<KRKN>("KRKN");
- add<KQKR>("KQKR");
- add<KBBKN>("KBBKN");
-
- add<KNPK>("KNPK");
- add<KRPKR>("KRPKR");
- add<KBPKB>("KBPKB");
- add<KBPKN>("KBPKN");
- add<KBPPKB>("KBPPKB");
- add<KRPPKRP>("KRPPKRP");
-}
-
-Endgames::~Endgames() {
-
- for_each(m1.begin(), m1.end(), delete_endgame<M1>);
- for_each(m2.begin(), m2.end(), delete_endgame<M2>);
-}
-
-template<EndgameType E>
-void Endgames::add(const string& code) {
-
- map((Endgame<E>*)0)[key(code, WHITE)] = new Endgame<E>(WHITE);
- map((Endgame<E>*)0)[key(code, BLACK)] = new Endgame<E>(BLACK);
-}
-
-
-/// Mate with KX vs K. This function is used to evaluate positions with
-/// King and plenty of material vs a lone king. It simply gives the
-/// 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 Endgame<KXK>::operator()(const Position& pos) const {
-
- assert(pos.non_pawn_material(weakerSide) == VALUE_ZERO);
- assert(pos.piece_count(weakerSide, PAWN) == VALUE_ZERO);
-
- // Stalemate detection with lone king
- if ( pos.side_to_move() == weakerSide
- && !pos.in_check()
- && !MoveList<LEGAL>(pos).size()) {
- return VALUE_DRAW;
- }
-
- Square winnerKSq = pos.king_square(strongerSide);
- Square loserKSq = pos.king_square(weakerSide);
-
- Value result = pos.non_pawn_material(strongerSide)
- + pos.piece_count(strongerSide, PAWN) * PawnValueEg
- + MateTable[loserKSq]
- + DistanceBonus[square_distance(winnerKSq, loserKSq)];
-
- if ( pos.piece_count(strongerSide, QUEEN)
- || pos.piece_count(strongerSide, ROOK)
- || pos.bishop_pair(strongerSide)) {
- result += VALUE_KNOWN_WIN;
- }
-
- return strongerSide == 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 Endgame<KBNK>::operator()(const Position& pos) const {
-
- assert(pos.non_pawn_material(weakerSide) == VALUE_ZERO);
- assert(pos.piece_count(weakerSide, PAWN) == VALUE_ZERO);
- assert(pos.non_pawn_material(strongerSide) == KnightValueMg + BishopValueMg);
- assert(pos.piece_count(strongerSide, BISHOP) == 1);
- assert(pos.piece_count(strongerSide, KNIGHT) == 1);
- assert(pos.piece_count(strongerSide, PAWN) == 0);
-
- Square winnerKSq = pos.king_square(strongerSide);
- Square loserKSq = pos.king_square(weakerSide);
- Square bishopSquare = pos.piece_list(strongerSide, BISHOP)[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.
- if (opposite_colors(bishopSquare, SQ_A1))
- {
- winnerKSq = mirror(winnerKSq);
- loserKSq = mirror(loserKSq);
- }
-
- Value result = VALUE_KNOWN_WIN
- + DistanceBonus[square_distance(winnerKSq, loserKSq)]
- + KBNKMateTable[loserKSq];
-
- return strongerSide == pos.side_to_move() ? result : -result;
-}
-
-
-/// KP vs K. This endgame is evaluated with the help of a bitbase.
-template<>
-Value Endgame<KPK>::operator()(const Position& pos) const {
-
- assert(pos.non_pawn_material(strongerSide) == VALUE_ZERO);
- assert(pos.non_pawn_material(weakerSide) == VALUE_ZERO);
- assert(pos.piece_count(strongerSide, PAWN) == 1);
- assert(pos.piece_count(weakerSide, PAWN) == 0);
-
- 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 = ~pos.king_square(BLACK);
- bksq = ~pos.king_square(WHITE);
- wpsq = ~pos.piece_list(BLACK, PAWN)[0];
- stm = ~pos.side_to_move();
- }
-
- if (file_of(wpsq) >= FILE_E)
- {
- wksq = mirror(wksq);
- bksq = mirror(bksq);
- wpsq = mirror(wpsq);
- }
-
- if (!Bitbases::probe_kpk(wksq, wpsq, bksq, stm))
- return VALUE_DRAW;
-
- Value result = VALUE_KNOWN_WIN + PawnValueEg + Value(rank_of(wpsq));
-
- return strongerSide == pos.side_to_move() ? result : -result;
-}
-
-
-/// KR vs KP. This is a somewhat tricky endgame to evaluate precisely without
-/// a bitbase. The function below returns drawish scores when the pawn is
-/// far advanced with support of the king, while the attacking king is far
-/// away.
-template<>
-Value Endgame<KRKP>::operator()(const Position& pos) const {
-
- assert(pos.non_pawn_material(strongerSide) == RookValueMg);
- assert(pos.piece_count(strongerSide, PAWN) == 0);
- assert(pos.non_pawn_material(weakerSide) == 0);
- assert(pos.piece_count(weakerSide, PAWN) == 1);
-
- Square wksq, wrsq, bksq, bpsq;
- int tempo = (pos.side_to_move() == strongerSide);
-
- 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 = ~wksq;
- wrsq = ~wrsq;
- bksq = ~bksq;
- bpsq = ~bpsq;
- }
-
- Square queeningSq = file_of(bpsq) | 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 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));
-
- // 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
- && rank_of(wksq) >= RANK_4
- && square_distance(wksq, bpsq) - tempo > 2)
- result = Value(80 - square_distance(wksq, bpsq) * 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);
-
- return strongerSide == 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 Endgame<KRKB>::operator()(const Position& pos) const {
-
- assert(pos.non_pawn_material(strongerSide) == RookValueMg);
- assert(pos.piece_count(strongerSide, PAWN) == 0);
- assert(pos.non_pawn_material(weakerSide) == BishopValueMg);
- assert(pos.piece_count(weakerSide, PAWN) == 0);
- assert(pos.piece_count(weakerSide, BISHOP) == 1);
-
- Value result = Value(MateTable[pos.king_square(weakerSide)]);
- return strongerSide == 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 Endgame<KRKN>::operator()(const Position& pos) const {
-
- assert(pos.non_pawn_material(strongerSide) == RookValueMg);
- assert(pos.piece_count(strongerSide, PAWN) == 0);
- assert(pos.non_pawn_material(weakerSide) == KnightValueMg);
- assert(pos.piece_count(weakerSide, PAWN) == 0);
- assert(pos.piece_count(weakerSide, KNIGHT) == 1);
-
- const int penalty[8] = { 0, 10, 14, 20, 30, 42, 58, 80 };
-
- Square bksq = pos.king_square(weakerSide);
- Square bnsq = pos.piece_list(weakerSide, KNIGHT)[0];
- Value result = Value(MateTable[bksq] + penalty[square_distance(bksq, bnsq)]);
- return strongerSide == pos.side_to_move() ? result : -result;
-}
-
-
-/// KQ vs KR. This is almost identical to KX vs K: We give the attacking
-/// king a bonus for having the kings close together, and for forcing the
-/// defending king towards the edge. If we also take care to avoid null move
-/// for the defending side in the search, this is usually sufficient to be
-/// able to win KQ vs KR.
-template<>
-Value Endgame<KQKR>::operator()(const Position& pos) const {
-
- assert(pos.non_pawn_material(strongerSide) == QueenValueMg);
- assert(pos.piece_count(strongerSide, PAWN) == 0);
- assert(pos.non_pawn_material(weakerSide) == RookValueMg);
- assert(pos.piece_count(weakerSide, PAWN) == 0);
-
- Square winnerKSq = pos.king_square(strongerSide);
- Square loserKSq = pos.king_square(weakerSide);
-
- Value result = QueenValueEg
- - RookValueEg
- + MateTable[loserKSq]
- + DistanceBonus[square_distance(winnerKSq, loserKSq)];
-
- return strongerSide == pos.side_to_move() ? result : -result;
-}
-
-template<>
-Value Endgame<KBBKN>::operator()(const Position& pos) const {
-
- assert(pos.piece_count(strongerSide, BISHOP) == 2);
- assert(pos.non_pawn_material(strongerSide) == 2*BishopValueMg);
- assert(pos.piece_count(weakerSide, KNIGHT) == 1);
- assert(pos.non_pawn_material(weakerSide) == KnightValueMg);
- assert(!pos.pieces(PAWN));
-
- Value result = BishopValueEg;
- Square wksq = pos.king_square(strongerSide);
- Square bksq = pos.king_square(weakerSide);
- Square nsq = pos.piece_list(weakerSide, KNIGHT)[0];
-
- // Bonus for attacking king close to defending king
- result += Value(DistanceBonus[square_distance(wksq, bksq)]);
-
- // Bonus for driving the defending king and knight apart
- result += Value(square_distance(bksq, nsq) * 32);
-
- // Bonus for restricting the knight's mobility
- result += Value((8 - popcount<Max15>(pos.attacks_from<KNIGHT>(nsq))) * 8);
-
- return strongerSide == 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<KmmKm>::operator()(const Position&) const {
- return VALUE_DRAW;
-}
-
-template<>
-Value Endgame<KNNK>::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
-/// is returned. If not, the return value is SCALE_FACTOR_NONE, i.e. no scaling
-/// will be used.
-template<>
-ScaleFactor Endgame<KBPsK>::operator()(const Position& pos) const {
-
- assert(pos.non_pawn_material(strongerSide) == BishopValueMg);
- assert(pos.piece_count(strongerSide, BISHOP) == 1);
- assert(pos.piece_count(strongerSide, PAWN) >= 1);
-
- // No assertions about the material of weakerSide, 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.piece_list(strongerSide, PAWN)[0]);
-
- // All pawns are on a single rook file ?
- if ( (pawnFile == FILE_A || pawnFile == FILE_H)
- && !(pawns & ~file_bb(pawnFile)))
- {
- Square bishopSq = pos.piece_list(strongerSide, BISHOP)[0];
- Square queeningSq = relative_square(strongerSide, pawnFile | RANK_8);
- Square kingSq = pos.king_square(weakerSide);
-
- 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;
- }
- }
- return SCALE_FACTOR_NONE;
-}
-
-
-/// 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 Endgame<KQKRPs>::operator()(const Position& pos) const {
-
- assert(pos.non_pawn_material(strongerSide) == QueenValueMg);
- 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(weakerSide, ROOK) & rank_bb(relative_rank(weakerSide, RANK_3)))
- && (pos.pieces(weakerSide, PAWN) & rank_bb(relative_rank(weakerSide, RANK_2)))
- && (pos.attacks_from<KING>(kingSq) & pos.pieces(weakerSide, PAWN)))
- {
- Square rsq = pos.piece_list(weakerSide, ROOK)[0];
- if (pos.attacks_from<PAWN>(rsq, strongerSide) & pos.pieces(weakerSide, PAWN))
- return SCALE_FACTOR_DRAW;
- }
- return SCALE_FACTOR_NONE;
-}
-
-
-/// K, rook and one pawn vs K and a rook. This function knows a handful of the
-/// most important classes of drawn positions, but is far from perfect. It would
-/// probably be a good idea to add more knowledge in the future.
-///
-/// 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 Endgame<KRPKR>::operator()(const Position& pos) const {
-
- assert(pos.non_pawn_material(strongerSide) == RookValueMg);
- assert(pos.piece_count(strongerSide, PAWN) == 1);
- assert(pos.non_pawn_material(weakerSide) == RookValueMg);
- 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 = ~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);
- }
-
- File f = file_of(wpsq);
- Rank r = rank_of(wpsq);
- Square queeningSq = f | RANK_8;
- int tempo = (pos.side_to_move() == strongerSide);
-
- // 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
- && (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
- && 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
- && rank_of(brsq) == RANK_1
- && (!tempo || square_distance(wksq, wpsq) >= 2))
- return SCALE_FACTOR_DRAW;
-
- // White pawn on a7 and rook on a8 is a draw if black's king is on g7 or h7
- // 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))
- 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 + DELTA_N
- && square_distance(wksq, wpsq) - tempo >= 2
- && square_distance(wksq, brsq) - 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
- && (square_distance(wksq, queeningSq) < square_distance(bksq, queeningSq) - 2 + tempo)
- && (square_distance(wksq, queeningSq) < square_distance(bksq, wrsq) + tempo))
- return ScaleFactor(SCALE_FACTOR_MAX - 2 * square_distance(wksq, queeningSq));
-
- // Similar to the above, but with the pawn further back
- if ( f != FILE_A
- && file_of(wrsq) == f
- && wrsq < wpsq
- && (square_distance(wksq, queeningSq) < square_distance(bksq, queeningSq) - 2 + tempo)
- && (square_distance(wksq, wpsq + DELTA_N) < square_distance(bksq, wpsq + DELTA_N) - 2 + tempo)
- && ( square_distance(bksq, wrsq) + tempo >= 3
- || ( square_distance(wksq, queeningSq) < square_distance(bksq, wrsq) + tempo
- && (square_distance(wksq, wpsq + DELTA_N) < square_distance(bksq, wrsq) + tempo))))
- return ScaleFactor( SCALE_FACTOR_MAX
- - 8 * square_distance(wpsq, queeningSq)
- - 2 * square_distance(wksq, queeningSq));
-
- // If the pawn is not far advanced, and the defending king is somewhere in
- // the pawn's path, it's probably a draw.
- if (r <= RANK_4 && bksq > wpsq)
- {
- if (file_of(bksq) == file_of(wpsq))
- return ScaleFactor(10);
- if ( abs(file_of(bksq) - file_of(wpsq)) == 1
- && square_distance(wksq, bksq) > 2)
- return ScaleFactor(24 - 2 * square_distance(wksq, bksq));
- }
- 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 Endgame<KRPPKRP>::operator()(const Position& pos) const {
-
- assert(pos.non_pawn_material(strongerSide) == RookValueMg);
- assert(pos.piece_count(strongerSide, PAWN) == 2);
- assert(pos.non_pawn_material(weakerSide) == RookValueMg);
- assert(pos.piece_count(weakerSide, PAWN) == 1);
-
- Square wpsq1 = pos.piece_list(strongerSide, PAWN)[0];
- Square wpsq2 = pos.piece_list(strongerSide, PAWN)[1];
- Square bksq = pos.king_square(weakerSide);
-
- // Does the stronger side have a passed pawn?
- if ( pos.pawn_is_passed(strongerSide, wpsq1)
- || pos.pawn_is_passed(strongerSide, wpsq2))
- return SCALE_FACTOR_NONE;
-
- Rank r = std::max(relative_rank(strongerSide, wpsq1), relative_rank(strongerSide, wpsq2));
-
- if ( file_distance(bksq, wpsq1) <= 1
- && file_distance(bksq, wpsq2) <= 1
- && relative_rank(strongerSide, bksq) > r)
- {
- switch (r) {
- case RANK_2: return ScaleFactor(10);
- case RANK_3: return ScaleFactor(10);
- case RANK_4: return ScaleFactor(15);
- case RANK_5: return ScaleFactor(20);
- case RANK_6: return ScaleFactor(40);
- default: assert(false);
- }
- }
- return SCALE_FACTOR_NONE;
-}
-
-
-/// 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<KPsK>::operator()(const Position& pos) const {
-
- assert(pos.non_pawn_material(strongerSide) == VALUE_ZERO);
- assert(pos.piece_count(strongerSide, PAWN) >= 2);
- assert(pos.non_pawn_material(weakerSide) == VALUE_ZERO);
- assert(pos.piece_count(weakerSide, PAWN) == 0);
-
- Square ksq = pos.king_square(weakerSide);
- Bitboard pawns = pos.pieces(strongerSide, PAWN);
-
- // 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, 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, ksq) & pawns))
- return SCALE_FACTOR_DRAW;
- }
- return SCALE_FACTOR_NONE;
-}
-
-
-/// K, bishop and a pawn vs K and a bishop. There are two rules: If the defending
-/// king is somewhere along the path of the pawn, and the square of the king is
-/// not of the same color as the stronger side's bishop, it's a draw. If the two
-/// bishops have opposite color, it's almost always a draw.
-template<>
-ScaleFactor Endgame<KBPKB>::operator()(const Position& pos) const {
-
- assert(pos.non_pawn_material(strongerSide) == BishopValueMg);
- assert(pos.piece_count(strongerSide, BISHOP) == 1);
- assert(pos.piece_count(strongerSide, PAWN) == 1);
- assert(pos.non_pawn_material(weakerSide) == BishopValueMg);
- assert(pos.piece_count(weakerSide, BISHOP) == 1);
- assert(pos.piece_count(weakerSide, PAWN) == 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);
-
- // 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))
- return SCALE_FACTOR_DRAW;
-
- // Case 2: Opposite colored bishops
- if (opposite_colors(strongerBishopSq, weakerBishopSq))
- {
- // We assume that the position is drawn in the following three situations:
- //
- // a. The pawn is on rank 5 or further back.
- // b. The defending king is somewhere in the pawn's path.
- // c. The defending bishop attacks some square along the pawn's path,
- // and is at least three squares away from the pawn.
- //
- // These rules are probably not perfect, but in practice they work
- // reasonably well.
-
- if (relative_rank(strongerSide, pawnSq) <= RANK_5)
- return SCALE_FACTOR_DRAW;
- else
- {
- Bitboard path = forward_bb(strongerSide, pawnSq);
-
- if (path & pos.pieces(weakerSide, KING))
- return SCALE_FACTOR_DRAW;
-
- if ( (pos.attacks_from<BISHOP>(weakerBishopSq) & path)
- && square_distance(weakerBishopSq, pawnSq) >= 3)
- return SCALE_FACTOR_DRAW;
- }
- }
- return SCALE_FACTOR_NONE;
-}
-
-
-/// K, bishop and two pawns vs K and bishop. It detects a few basic draws with
-/// opposite-colored bishops.
-template<>
-ScaleFactor Endgame<KBPPKB>::operator()(const Position& pos) const {
-
- assert(pos.non_pawn_material(strongerSide) == BishopValueMg);
- assert(pos.piece_count(strongerSide, BISHOP) == 1);
- assert(pos.piece_count(strongerSide, PAWN) == 2);
- assert(pos.non_pawn_material(weakerSide) == BishopValueMg);
- assert(pos.piece_count(weakerSide, BISHOP) == 1);
- assert(pos.piece_count(weakerSide, PAWN) == 0);
-
- Square wbsq = pos.piece_list(strongerSide, BISHOP)[0];
- Square bbsq = pos.piece_list(weakerSide, BISHOP)[0];
-
- 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 = rank_of(psq1);
- Rank r2 = rank_of(psq2);
- Square blockSq1, blockSq2;
-
- if (relative_rank(strongerSide, psq1) > relative_rank(strongerSide, psq2))
- {
- blockSq1 = psq1 + pawn_push(strongerSide);
- blockSq2 = file_of(psq2) | rank_of(psq1);
- }
- else
- {
- blockSq1 = psq2 + pawn_push(strongerSide);
- blockSq2 = file_of(psq1) | rank_of(psq2);
- }
-
- switch (file_distance(psq1, psq2))
- {
- case 0:
- // Both pawns are on the same file. Easy draw if defender firmly controls
- // some square in the frontmost pawn's path.
- if ( file_of(ksq) == file_of(blockSq1)
- && relative_rank(strongerSide, ksq) >= relative_rank(strongerSide, blockSq1)
- && opposite_colors(ksq, wbsq))
- return SCALE_FACTOR_DRAW;
- else
- return SCALE_FACTOR_NONE;
-
- case 1:
- // Pawns on adjacent files. Draw if defender firmly controls the square
- // in front of the frontmost pawn's path, and the square diagonally behind
- // this square on the file of the other pawn.
- if ( ksq == blockSq1
- && opposite_colors(ksq, wbsq)
- && ( bbsq == blockSq2
- || (pos.attacks_from<BISHOP>(blockSq2) & pos.pieces(weakerSide, BISHOP))
- || abs(r1 - r2) >= 2))
- return SCALE_FACTOR_DRAW;
-
- else if ( ksq == blockSq2
- && opposite_colors(ksq, wbsq)
- && ( bbsq == blockSq1
- || (pos.attacks_from<BISHOP>(blockSq1) & pos.pieces(weakerSide, BISHOP))))
- return SCALE_FACTOR_DRAW;
- else
- return SCALE_FACTOR_NONE;
-
- default:
- // The pawns are not on the same file or adjacent files. No scaling.
- return SCALE_FACTOR_NONE;
- }
-}
-
-
-/// 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 Endgame<KBPKN>::operator()(const Position& pos) const {
-
- assert(pos.non_pawn_material(strongerSide) == BishopValueMg);
- assert(pos.piece_count(strongerSide, BISHOP) == 1);
- assert(pos.piece_count(strongerSide, PAWN) == 1);
- assert(pos.non_pawn_material(weakerSide) == KnightValueMg);
- assert(pos.piece_count(weakerSide, KNIGHT) == 1);
- assert(pos.piece_count(weakerSide, PAWN) == 0);
-
- Square pawnSq = pos.piece_list(strongerSide, PAWN)[0];
- Square strongerBishopSq = pos.piece_list(strongerSide, BISHOP)[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))
- return SCALE_FACTOR_DRAW;
-
- return SCALE_FACTOR_NONE;
-}
-
-
-/// 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 Endgame<KNPK>::operator()(const Position& pos) const {
-
- assert(pos.non_pawn_material(strongerSide) == KnightValueMg);
- assert(pos.piece_count(strongerSide, KNIGHT) == 1);
- assert(pos.piece_count(strongerSide, PAWN) == 1);
- assert(pos.non_pawn_material(weakerSide) == VALUE_ZERO);
- assert(pos.piece_count(weakerSide, PAWN) == 0);
-
- Square pawnSq = pos.piece_list(strongerSide, PAWN)[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;
-
- if ( pawnSq == relative_square(strongerSide, SQ_H7)
- && square_distance(weakerKingSq, relative_square(strongerSide, SQ_H8)) <= 1)
- return SCALE_FACTOR_DRAW;
-
- return SCALE_FACTOR_NONE;
-}
-
-
-/// K and a pawn vs K and a pawn. This is done by removing the weakest side's
-/// pawn and probing the KP vs K bitbase: If the weakest side has a draw without
-/// the pawn, she probably has at least a draw with the pawn as well. The exception
-/// is when the stronger side's pawn is far advanced and not on a rook file; in
-/// this case it is often possible to win (e.g. 8/4k3/3p4/3P4/6K1/8/8/8 w - - 0 1).
-template<>
-ScaleFactor Endgame<KPKP>::operator()(const Position& pos) const {
-
- assert(pos.non_pawn_material(strongerSide) == VALUE_ZERO);
- assert(pos.non_pawn_material(weakerSide) == VALUE_ZERO);
- assert(pos.piece_count(WHITE, PAWN) == 1);
- assert(pos.piece_count(BLACK, PAWN) == 1);
-
- Square wksq = pos.king_square(strongerSide);
- Square bksq = pos.king_square(weakerSide);
- Square wpsq = pos.piece_list(strongerSide, PAWN)[0];
- Color stm = pos.side_to_move();
-
- if (strongerSide == BLACK)
- {
- wksq = ~wksq;
- bksq = ~bksq;
- wpsq = ~wpsq;
- stm = ~stm;
- }
-
- if (file_of(wpsq) >= FILE_E)
- {
- wksq = mirror(wksq);
- bksq = mirror(bksq);
- wpsq = mirror(wpsq);
- }
-
- // 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)
- 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, stm) ? SCALE_FACTOR_NONE : SCALE_FACTOR_DRAW;
-}
projects / stockfish / blobdiff