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> Bitboard pieces(PieceType pt, PieceTypes... pts) const;
93 Bitboard pieces(Color c) const;
94 template<typename ...PieceTypes> Bitboard pieces(Color c, PieceTypes... pts) const;
95 Piece piece_on(Square s) const;
96 Square ep_square() const;
97 bool empty(Square s) const;
98 template<PieceType Pt> int count(Color c) const;
99 template<PieceType Pt> int count() const;
100 template<PieceType Pt> Square square(Color c) const;
103 CastlingRights castling_rights(Color c) const;
104 bool can_castle(CastlingRights cr) const;
105 bool castling_impeded(CastlingRights cr) const;
106 Square castling_rook_square(CastlingRights cr) const;
109 Bitboard checkers() const;
110 Bitboard blockers_for_king(Color c) const;
111 Bitboard check_squares(PieceType pt) const;
112 Bitboard pinners(Color c) const;
114 // Attacks to/from a given square
115 Bitboard attackers_to(Square s) const;
116 Bitboard attackers_to(Square s, Bitboard occupied) const;
117 void update_slider_blockers(Color c) const;
118 template<PieceType Pt> Bitboard attacks_by(Color c) const;
120 // Properties of moves
121 bool legal(Move m) const;
122 bool pseudo_legal(const Move m) const;
123 bool capture(Move m) const;
124 bool capture_stage(Move m) const;
125 bool gives_check(Move m) const;
126 Piece moved_piece(Move m) const;
127 Piece captured_piece() const;
129 // Doing and undoing moves
130 void do_move(Move m, StateInfo& newSt);
131 void do_move(Move m, StateInfo& newSt, bool givesCheck);
132 void undo_move(Move m);
133 void do_null_move(StateInfo& newSt);
134 void undo_null_move();
136 // Static Exchange Evaluation
137 bool see_ge(Move m, Value threshold = VALUE_ZERO) const;
138 bool see_ge(Move m, Bitboard& occupied, Value threshold = VALUE_ZERO) const;
140 // Accessing hash keys
142 Key key_after(Move m) const;
143 Key material_key() const;
145 // Other properties of the position
146 Color side_to_move() const;
147 int game_ply() const;
148 bool is_chess960() const;
149 Thread* this_thread() const;
150 bool is_draw(int ply) const;
151 bool has_game_cycle(int ply) const;
152 bool has_repeated() const;
153 int rule50_count() const;
154 Value non_pawn_material(Color c) const;
155 Value non_pawn_material() const;
157 // Position consistency check, for debugging
158 bool pos_is_ok() const;
162 StateInfo* state() const;
164 void put_piece(Piece pc, Square s);
165 void remove_piece(Square s);
168 // Initialization helpers (used while setting up a position)
169 void set_castling_right(Color c, Square rfrom);
170 void set_state() const;
171 void set_check_info() const;
174 void move_piece(Square from, Square to);
176 void do_castling(Color us, Square from, Square& to, Square& rfrom, Square& rto);
177 template<bool AfterMove>
178 Key adjust_key50(Key k) const;
181 Piece board[SQUARE_NB];
182 Bitboard byTypeBB[PIECE_TYPE_NB];
183 Bitboard byColorBB[COLOR_NB];
184 int pieceCount[PIECE_NB];
185 int castlingRightsMask[SQUARE_NB];
186 Square castlingRookSquare[CASTLING_RIGHT_NB];
187 Bitboard castlingPath[CASTLING_RIGHT_NB];
195 std::ostream& operator<<(std::ostream& os, const Position& pos);
197 inline Color Position::side_to_move() const {
201 inline Piece Position::piece_on(Square s) const {
206 inline bool Position::empty(Square s) const {
207 return piece_on(s) == NO_PIECE;
210 inline Piece Position::moved_piece(Move m) const {
211 return piece_on(from_sq(m));
214 inline Bitboard Position::pieces(PieceType pt) const {
218 template<typename ...PieceTypes>
219 inline Bitboard Position::pieces(PieceType pt, PieceTypes... pts) const {
220 return pieces(pt) | pieces(pts...);
223 inline Bitboard Position::pieces(Color c) const {
227 template<typename ...PieceTypes>
228 inline Bitboard Position::pieces(Color c, PieceTypes... pts) const {
229 return pieces(c) & pieces(pts...);
232 template<PieceType Pt> inline int Position::count(Color c) const {
233 return pieceCount[make_piece(c, Pt)];
236 template<PieceType Pt> inline int Position::count() const {
237 return count<Pt>(WHITE) + count<Pt>(BLACK);
240 template<PieceType Pt> inline Square Position::square(Color c) const {
241 assert(count<Pt>(c) == 1);
242 return lsb(pieces(c, Pt));
245 inline Square Position::ep_square() const {
249 inline bool Position::can_castle(CastlingRights cr) const {
250 return st->castlingRights & cr;
253 inline CastlingRights Position::castling_rights(Color c) const {
254 return c & CastlingRights(st->castlingRights);
257 inline bool Position::castling_impeded(CastlingRights cr) const {
258 assert(cr == WHITE_OO || cr == WHITE_OOO || cr == BLACK_OO || cr == BLACK_OOO);
260 return pieces() & castlingPath[cr];
263 inline Square Position::castling_rook_square(CastlingRights cr) const {
264 assert(cr == WHITE_OO || cr == WHITE_OOO || cr == BLACK_OO || cr == BLACK_OOO);
266 return castlingRookSquare[cr];
269 inline Bitboard Position::attackers_to(Square s) const {
270 return attackers_to(s, pieces());
273 template<PieceType Pt>
274 inline Bitboard Position::attacks_by(Color c) const {
276 if constexpr (Pt == PAWN)
277 return c == WHITE ? pawn_attacks_bb<WHITE>(pieces(WHITE, PAWN))
278 : pawn_attacks_bb<BLACK>(pieces(BLACK, PAWN));
281 Bitboard threats = 0;
282 Bitboard attackers = pieces(c, Pt);
284 threats |= attacks_bb<Pt>(pop_lsb(attackers), pieces());
289 inline Bitboard Position::checkers() const {
290 return st->checkersBB;
293 inline Bitboard Position::blockers_for_king(Color c) const {
294 return st->blockersForKing[c];
297 inline Bitboard Position::pinners(Color c) const {
298 return st->pinners[c];
301 inline Bitboard Position::check_squares(PieceType pt) const {
302 return st->checkSquares[pt];
305 inline Key Position::key() const {
306 return adjust_key50<false>(st->key);
309 template<bool AfterMove>
310 inline Key Position::adjust_key50(Key k) const
312 return st->rule50 < 14 - AfterMove
313 ? k : k ^ make_key((st->rule50 - (14 - AfterMove)) / 8);
316 inline Key Position::material_key() const {
317 return st->materialKey;
320 inline Value Position::non_pawn_material(Color c) const {
321 return st->nonPawnMaterial[c];
324 inline Value Position::non_pawn_material() const {
325 return non_pawn_material(WHITE) + non_pawn_material(BLACK);
328 inline int Position::game_ply() const {
332 inline int Position::rule50_count() const {
336 inline bool Position::is_chess960() const {
340 inline bool Position::capture(Move m) const {
342 return (!empty(to_sq(m)) && type_of(m) != CASTLING)
343 || type_of(m) == EN_PASSANT;
346 // returns true if a move is generated from the capture stage
347 // having also queen promotions covered, i.e. consistency with the capture stage move generation
348 // is needed to avoid the generation of duplicate moves.
349 inline bool Position::capture_stage(Move m) const {
351 return capture(m) || promotion_type(m) == QUEEN;
354 inline Piece Position::captured_piece() const {
355 return st->capturedPiece;
358 inline Thread* Position::this_thread() const {
362 inline void Position::put_piece(Piece pc, Square s) {
365 byTypeBB[ALL_PIECES] |= byTypeBB[type_of(pc)] |= s;
366 byColorBB[color_of(pc)] |= s;
368 pieceCount[make_piece(color_of(pc), ALL_PIECES)]++;
371 inline void Position::remove_piece(Square s) {
374 byTypeBB[ALL_PIECES] ^= s;
375 byTypeBB[type_of(pc)] ^= s;
376 byColorBB[color_of(pc)] ^= s;
379 pieceCount[make_piece(color_of(pc), ALL_PIECES)]--;
382 inline void Position::move_piece(Square from, Square to) {
384 Piece pc = board[from];
385 Bitboard fromTo = from | to;
386 byTypeBB[ALL_PIECES] ^= fromTo;
387 byTypeBB[type_of(pc)] ^= fromTo;
388 byColorBB[color_of(pc)] ^= fromTo;
389 board[from] = NO_PIECE;
393 inline void Position::do_move(Move m, StateInfo& newSt) {
394 do_move(m, newSt, gives_check(m));
397 inline StateInfo* Position::state() const {
402 } // namespace Stockfish
404 #endif // #ifndef POSITION_H_INCLUDED