2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2023 The Stockfish developers (see AUTHORS file)
5 Stockfish is free software: you can redistribute it and/or modify
6 it under the terms of the GNU General Public License as published by
7 the Free Software Foundation, either version 3 of the License, or
8 (at your option) any later version.
10 Stockfish is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 GNU General Public License for more details.
15 You should have received a copy of the GNU General Public License
16 along with this program. If not, see <http://www.gnu.org/licenses/>.
19 #ifndef POSITION_H_INCLUDED
20 #define POSITION_H_INCLUDED
29 #include "nnue/nnue_accumulator.h"
34 // StateInfo struct stores information needed to restore a Position object to
35 // its previous state when we retract a move. Whenever a move is made on the
36 // board (by calling Position::do_move), a StateInfo object must be passed.
40 // Copied when making a move
42 Value nonPawnMaterial[COLOR_NB];
48 // Not copied when making a move (will be recomputed anyhow)
52 Bitboard blockersForKing[COLOR_NB];
53 Bitboard pinners[COLOR_NB];
54 Bitboard checkSquares[PIECE_TYPE_NB];
59 Eval::NNUE::Accumulator accumulator;
60 DirtyPiece dirtyPiece;
64 // A list to keep track of the position states along the setup moves (from the
65 // start position to the position just before the search starts). Needed by
66 // 'draw by repetition' detection. Use a std::deque because pointers to
67 // elements are not invalidated upon list resizing.
68 using StateListPtr = std::unique_ptr<std::deque<StateInfo>>;
71 // Position class stores information regarding the board representation as
72 // pieces, side to move, hash keys, castling info, etc. Important methods are
73 // do_move() and undo_move(), used by the search to update node info when
74 // traversing the search tree.
82 Position(const Position&) = delete;
83 Position& operator=(const Position&) = delete;
85 // FEN string input/output
86 Position& set(const std::string& fenStr, bool isChess960, StateInfo* si, Thread* th);
87 Position& set(const std::string& code, Color c, StateInfo* si);
88 std::string fen() const;
90 // Position representation
91 Bitboard pieces(PieceType pt = ALL_PIECES) const;
92 template<typename... PieceTypes>
93 Bitboard pieces(PieceType pt, PieceTypes... pts) const;
94 Bitboard pieces(Color c) const;
95 template<typename... PieceTypes>
96 Bitboard pieces(Color c, PieceTypes... pts) const;
97 Piece piece_on(Square s) const;
98 Square ep_square() const;
99 bool empty(Square s) const;
100 template<PieceType Pt>
101 int count(Color c) const;
102 template<PieceType Pt>
104 template<PieceType Pt>
105 Square square(Color c) const;
108 CastlingRights castling_rights(Color c) const;
109 bool can_castle(CastlingRights cr) const;
110 bool castling_impeded(CastlingRights cr) const;
111 Square castling_rook_square(CastlingRights cr) const;
114 Bitboard checkers() const;
115 Bitboard blockers_for_king(Color c) const;
116 Bitboard check_squares(PieceType pt) const;
117 Bitboard pinners(Color c) const;
119 // Attacks to/from a given square
120 Bitboard attackers_to(Square s) const;
121 Bitboard attackers_to(Square s, Bitboard occupied) const;
122 void update_slider_blockers(Color c) const;
123 template<PieceType Pt>
124 Bitboard attacks_by(Color c) const;
126 // Properties of moves
127 bool legal(Move m) const;
128 bool pseudo_legal(const Move m) const;
129 bool capture(Move m) const;
130 bool capture_stage(Move m) const;
131 bool gives_check(Move m) const;
132 Piece moved_piece(Move m) const;
133 Piece captured_piece() const;
135 // Doing and undoing moves
136 void do_move(Move m, StateInfo& newSt);
137 void do_move(Move m, StateInfo& newSt, bool givesCheck);
138 void undo_move(Move m);
139 void do_null_move(StateInfo& newSt);
140 void undo_null_move();
142 // Static Exchange Evaluation
143 bool see_ge(Move m, Value threshold = VALUE_ZERO) const;
145 // Accessing hash keys
147 Key key_after(Move m) const;
148 Key material_key() const;
150 // Other properties of the position
151 Color side_to_move() const;
152 int game_ply() const;
153 bool is_chess960() const;
154 Thread* this_thread() const;
155 bool is_draw(int ply) const;
156 bool has_game_cycle(int ply) const;
157 bool has_repeated() const;
158 int rule50_count() const;
159 Value non_pawn_material(Color c) const;
160 Value non_pawn_material() const;
162 // Position consistency check, for debugging
163 bool pos_is_ok() const;
167 StateInfo* state() const;
169 void put_piece(Piece pc, Square s);
170 void remove_piece(Square s);
173 // Initialization helpers (used while setting up a position)
174 void set_castling_right(Color c, Square rfrom);
175 void set_state() const;
176 void set_check_info() const;
179 void move_piece(Square from, Square to);
181 void do_castling(Color us, Square from, Square& to, Square& rfrom, Square& rto);
182 template<bool AfterMove>
183 Key adjust_key50(Key k) const;
186 Piece board[SQUARE_NB];
187 Bitboard byTypeBB[PIECE_TYPE_NB];
188 Bitboard byColorBB[COLOR_NB];
189 int pieceCount[PIECE_NB];
190 int castlingRightsMask[SQUARE_NB];
191 Square castlingRookSquare[CASTLING_RIGHT_NB];
192 Bitboard castlingPath[CASTLING_RIGHT_NB];
200 std::ostream& operator<<(std::ostream& os, const Position& pos);
202 inline Color Position::side_to_move() const { return sideToMove; }
204 inline Piece Position::piece_on(Square s) const {
209 inline bool Position::empty(Square s) const { return piece_on(s) == NO_PIECE; }
211 inline Piece Position::moved_piece(Move m) const { return piece_on(from_sq(m)); }
213 inline Bitboard Position::pieces(PieceType pt) const { return byTypeBB[pt]; }
215 template<typename... PieceTypes>
216 inline Bitboard Position::pieces(PieceType pt, PieceTypes... pts) const {
217 return pieces(pt) | pieces(pts...);
220 inline Bitboard Position::pieces(Color c) const { return byColorBB[c]; }
222 template<typename... PieceTypes>
223 inline Bitboard Position::pieces(Color c, PieceTypes... pts) const {
224 return pieces(c) & pieces(pts...);
227 template<PieceType Pt>
228 inline int Position::count(Color c) const {
229 return pieceCount[make_piece(c, Pt)];
232 template<PieceType Pt>
233 inline int Position::count() const {
234 return count<Pt>(WHITE) + count<Pt>(BLACK);
237 template<PieceType Pt>
238 inline Square Position::square(Color c) const {
239 assert(count<Pt>(c) == 1);
240 return lsb(pieces(c, Pt));
243 inline Square Position::ep_square() const { return st->epSquare; }
245 inline bool Position::can_castle(CastlingRights cr) const { return st->castlingRights & cr; }
247 inline CastlingRights Position::castling_rights(Color c) const {
248 return c & CastlingRights(st->castlingRights);
251 inline bool Position::castling_impeded(CastlingRights cr) const {
252 assert(cr == WHITE_OO || cr == WHITE_OOO || cr == BLACK_OO || cr == BLACK_OOO);
254 return pieces() & castlingPath[cr];
257 inline Square Position::castling_rook_square(CastlingRights cr) const {
258 assert(cr == WHITE_OO || cr == WHITE_OOO || cr == BLACK_OO || cr == BLACK_OOO);
260 return castlingRookSquare[cr];
263 inline Bitboard Position::attackers_to(Square s) const { return attackers_to(s, pieces()); }
265 template<PieceType Pt>
266 inline Bitboard Position::attacks_by(Color c) const {
268 if constexpr (Pt == PAWN)
269 return c == WHITE ? pawn_attacks_bb<WHITE>(pieces(WHITE, PAWN))
270 : pawn_attacks_bb<BLACK>(pieces(BLACK, PAWN));
273 Bitboard threats = 0;
274 Bitboard attackers = pieces(c, Pt);
276 threats |= attacks_bb<Pt>(pop_lsb(attackers), pieces());
281 inline Bitboard Position::checkers() const { return st->checkersBB; }
283 inline Bitboard Position::blockers_for_king(Color c) const { return st->blockersForKing[c]; }
285 inline Bitboard Position::pinners(Color c) const { return st->pinners[c]; }
287 inline Bitboard Position::check_squares(PieceType pt) const { return st->checkSquares[pt]; }
289 inline Key Position::key() const { return adjust_key50<false>(st->key); }
291 template<bool AfterMove>
292 inline Key Position::adjust_key50(Key k) const {
293 return st->rule50 < 14 - AfterMove ? k : k ^ make_key((st->rule50 - (14 - AfterMove)) / 8);
296 inline Key Position::material_key() const { return st->materialKey; }
298 inline Value Position::non_pawn_material(Color c) const { return st->nonPawnMaterial[c]; }
300 inline Value Position::non_pawn_material() const {
301 return non_pawn_material(WHITE) + non_pawn_material(BLACK);
304 inline int Position::game_ply() const { return gamePly; }
306 inline int Position::rule50_count() const { return st->rule50; }
308 inline bool Position::is_chess960() const { return chess960; }
310 inline bool Position::capture(Move m) const {
312 return (!empty(to_sq(m)) && type_of(m) != CASTLING) || type_of(m) == EN_PASSANT;
315 // Returns true if a move is generated from the capture stage, having also
316 // queen promotions covered, i.e. consistency with the capture stage move generation
317 // is needed to avoid the generation of duplicate moves.
318 inline bool Position::capture_stage(Move m) const {
320 return capture(m) || promotion_type(m) == QUEEN;
323 inline Piece Position::captured_piece() const { return st->capturedPiece; }
325 inline Thread* Position::this_thread() const { return thisThread; }
327 inline void Position::put_piece(Piece pc, Square s) {
330 byTypeBB[ALL_PIECES] |= byTypeBB[type_of(pc)] |= s;
331 byColorBB[color_of(pc)] |= s;
333 pieceCount[make_piece(color_of(pc), ALL_PIECES)]++;
336 inline void Position::remove_piece(Square s) {
339 byTypeBB[ALL_PIECES] ^= s;
340 byTypeBB[type_of(pc)] ^= s;
341 byColorBB[color_of(pc)] ^= s;
344 pieceCount[make_piece(color_of(pc), ALL_PIECES)]--;
347 inline void Position::move_piece(Square from, Square to) {
349 Piece pc = board[from];
350 Bitboard fromTo = from | to;
351 byTypeBB[ALL_PIECES] ^= fromTo;
352 byTypeBB[type_of(pc)] ^= fromTo;
353 byColorBB[color_of(pc)] ^= fromTo;
354 board[from] = NO_PIECE;
358 inline void Position::do_move(Move m, StateInfo& newSt) { do_move(m, newSt, gives_check(m)); }
360 inline StateInfo* Position::state() const { return st; }
362 } // namespace Stockfish
364 #endif // #ifndef POSITION_H_INCLUDED