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
24 #include <memory> // For std::unique_ptr
31 #include "nnue/nnue_accumulator.h"
35 /// StateInfo struct stores information needed to restore a Position object to
36 /// its previous state when we retract a move. Whenever a move is made on the
37 /// board (by calling Position::do_move), a StateInfo object must be passed.
41 // Copied when making a move
43 Value nonPawnMaterial[COLOR_NB];
49 // Not copied when making a move (will be recomputed anyhow)
53 Bitboard blockersForKing[COLOR_NB];
54 Bitboard pinners[COLOR_NB];
55 Bitboard checkSquares[PIECE_TYPE_NB];
60 Eval::NNUE::Accumulator accumulator;
61 DirtyPiece dirtyPiece;
65 /// A list to keep track of the position states along the setup moves (from the
66 /// start position to the position just before the search starts). Needed by
67 /// 'draw by repetition' detection. Use a std::deque because pointers to
68 /// elements are not invalidated upon list resizing.
69 using StateListPtr = std::unique_ptr<std::deque<StateInfo>>;
72 /// Position class stores information regarding the board representation as
73 /// pieces, side to move, hash keys, castling info, etc. Important methods are
74 /// do_move() and undo_move(), used by the search to update node info when
75 /// traversing the search tree.
83 Position(const Position&) = delete;
84 Position& operator=(const Position&) = delete;
86 // FEN string input/output
87 Position& set(const std::string& fenStr, bool isChess960, StateInfo* si, Thread* th);
88 Position& set(const std::string& code, Color c, StateInfo* si);
89 std::string fen() const;
91 // Position representation
92 Bitboard pieces(PieceType pt = ALL_PIECES) const;
93 template<typename ...PieceTypes> Bitboard pieces(PieceType pt, PieceTypes... pts) const;
94 Bitboard pieces(Color c) const;
95 template<typename ...PieceTypes> Bitboard pieces(Color c, PieceTypes... pts) const;
96 Piece piece_on(Square s) const;
97 Square ep_square() const;
98 bool empty(Square s) const;
99 template<PieceType Pt> int count(Color c) const;
100 template<PieceType Pt> int count() const;
101 template<PieceType Pt> Square square(Color c) const;
104 CastlingRights castling_rights(Color c) const;
105 bool can_castle(CastlingRights cr) const;
106 bool castling_impeded(CastlingRights cr) const;
107 Square castling_rook_square(CastlingRights cr) const;
110 Bitboard checkers() const;
111 Bitboard blockers_for_king(Color c) const;
112 Bitboard check_squares(PieceType pt) const;
113 Bitboard pinners(Color c) const;
115 // Attacks to/from a given square
116 Bitboard attackers_to(Square s) const;
117 Bitboard attackers_to(Square s, Bitboard occupied) const;
118 Bitboard slider_blockers(Bitboard sliders, Square s, Bitboard& pinners) const;
119 template<PieceType Pt> Bitboard attacks_by(Color c) const;
121 // Properties of moves
122 bool legal(Move m) const;
123 bool pseudo_legal(const Move m) const;
124 bool capture(Move m) const;
125 bool capture_stage(Move m) const;
126 bool gives_check(Move m) const;
127 Piece moved_piece(Move m) const;
128 Piece captured_piece() const;
130 // Doing and undoing moves
131 void do_move(Move m, StateInfo& newSt);
132 void do_move(Move m, StateInfo& newSt, bool givesCheck);
133 void undo_move(Move m);
134 void do_null_move(StateInfo& newSt);
135 void undo_null_move();
137 // Static Exchange Evaluation
138 bool see_ge(Move m, Value threshold = VALUE_ZERO) const;
139 bool see_ge(Move m, Bitboard& occupied, Value threshold = VALUE_ZERO) const;
141 // Accessing hash keys
143 Key key_after(Move m) const;
144 Key material_key() const;
146 // Other properties of the position
147 Color side_to_move() const;
148 int game_ply() const;
149 bool is_chess960() const;
150 Thread* this_thread() const;
151 bool is_draw(int ply) const;
152 bool has_game_cycle(int ply) const;
153 bool has_repeated() const;
154 int rule50_count() const;
155 Value non_pawn_material(Color c) const;
156 Value non_pawn_material() const;
158 // Position consistency check, for debugging
159 bool pos_is_ok() const;
163 StateInfo* state() const;
165 void put_piece(Piece pc, Square s);
166 void remove_piece(Square s);
169 // Initialization helpers (used while setting up a position)
170 void set_castling_right(Color c, Square rfrom);
171 void set_state() const;
172 void set_check_info() const;
175 void move_piece(Square from, Square to);
177 void do_castling(Color us, Square from, Square& to, Square& rfrom, Square& rto);
178 template<bool AfterMove>
179 Key adjust_key50(Key k) const;
182 Piece board[SQUARE_NB];
183 Bitboard byTypeBB[PIECE_TYPE_NB];
184 Bitboard byColorBB[COLOR_NB];
185 int pieceCount[PIECE_NB];
186 int castlingRightsMask[SQUARE_NB];
187 Square castlingRookSquare[CASTLING_RIGHT_NB];
188 Bitboard castlingPath[CASTLING_RIGHT_NB];
196 std::ostream& operator<<(std::ostream& os, const Position& pos);
198 inline Color Position::side_to_move() const {
202 inline Piece Position::piece_on(Square s) const {
207 inline bool Position::empty(Square s) const {
208 return piece_on(s) == NO_PIECE;
211 inline Piece Position::moved_piece(Move m) const {
212 return piece_on(from_sq(m));
215 inline Bitboard Position::pieces(PieceType pt) const {
219 template<typename ...PieceTypes>
220 inline Bitboard Position::pieces(PieceType pt, PieceTypes... pts) const {
221 return pieces(pt) | pieces(pts...);
224 inline Bitboard Position::pieces(Color c) const {
228 template<typename ...PieceTypes>
229 inline Bitboard Position::pieces(Color c, PieceTypes... pts) const {
230 return pieces(c) & pieces(pts...);
233 template<PieceType Pt> inline int Position::count(Color c) const {
234 return pieceCount[make_piece(c, Pt)];
237 template<PieceType Pt> inline int Position::count() const {
238 return count<Pt>(WHITE) + count<Pt>(BLACK);
241 template<PieceType Pt> inline Square Position::square(Color c) const {
242 assert(count<Pt>(c) == 1);
243 return lsb(pieces(c, Pt));
246 inline Square Position::ep_square() const {
250 inline bool Position::can_castle(CastlingRights cr) const {
251 return st->castlingRights & cr;
254 inline CastlingRights Position::castling_rights(Color c) const {
255 return c & CastlingRights(st->castlingRights);
258 inline bool Position::castling_impeded(CastlingRights cr) const {
259 assert(cr == WHITE_OO || cr == WHITE_OOO || cr == BLACK_OO || cr == BLACK_OOO);
261 return pieces() & castlingPath[cr];
264 inline Square Position::castling_rook_square(CastlingRights cr) const {
265 assert(cr == WHITE_OO || cr == WHITE_OOO || cr == BLACK_OO || cr == BLACK_OOO);
267 return castlingRookSquare[cr];
270 inline Bitboard Position::attackers_to(Square s) const {
271 return attackers_to(s, pieces());
274 template<PieceType Pt>
275 inline Bitboard Position::attacks_by(Color c) const {
277 if constexpr (Pt == PAWN)
278 return c == WHITE ? pawn_attacks_bb<WHITE>(pieces(WHITE, PAWN))
279 : pawn_attacks_bb<BLACK>(pieces(BLACK, PAWN));
282 Bitboard threats = 0;
283 Bitboard attackers = pieces(c, Pt);
285 threats |= attacks_bb<Pt>(pop_lsb(attackers), pieces());
290 inline Bitboard Position::checkers() const {
291 return st->checkersBB;
294 inline Bitboard Position::blockers_for_king(Color c) const {
295 return st->blockersForKing[c];
298 inline Bitboard Position::pinners(Color c) const {
299 return st->pinners[c];
302 inline Bitboard Position::check_squares(PieceType pt) const {
303 return st->checkSquares[pt];
306 inline Key Position::key() const {
307 return adjust_key50<false>(st->key);
310 template<bool AfterMove>
311 inline Key Position::adjust_key50(Key k) const
313 return st->rule50 < 14 - AfterMove
314 ? k : k ^ make_key((st->rule50 - (14 - AfterMove)) / 8);
317 inline Key Position::material_key() const {
318 return st->materialKey;
321 inline Value Position::non_pawn_material(Color c) const {
322 return st->nonPawnMaterial[c];
325 inline Value Position::non_pawn_material() const {
326 return non_pawn_material(WHITE) + non_pawn_material(BLACK);
329 inline int Position::game_ply() const {
333 inline int Position::rule50_count() const {
337 inline bool Position::is_chess960() const {
341 inline bool Position::capture(Move m) const {
343 return (!empty(to_sq(m)) && type_of(m) != CASTLING)
344 || type_of(m) == EN_PASSANT;
347 // returns true if a move is generated from the capture stage
348 // having also queen promotions covered, i.e. consistency with the capture stage move generation
349 // is needed to avoid the generation of duplicate moves.
350 inline bool Position::capture_stage(Move m) const {
352 return capture(m) || promotion_type(m) == QUEEN;
355 inline Piece Position::captured_piece() const {
356 return st->capturedPiece;
359 inline Thread* Position::this_thread() const {
363 inline void Position::put_piece(Piece pc, Square s) {
366 byTypeBB[ALL_PIECES] |= byTypeBB[type_of(pc)] |= s;
367 byColorBB[color_of(pc)] |= s;
369 pieceCount[make_piece(color_of(pc), ALL_PIECES)]++;
372 inline void Position::remove_piece(Square s) {
375 byTypeBB[ALL_PIECES] ^= s;
376 byTypeBB[type_of(pc)] ^= s;
377 byColorBB[color_of(pc)] ^= s;
380 pieceCount[make_piece(color_of(pc), ALL_PIECES)]--;
383 inline void Position::move_piece(Square from, Square to) {
385 Piece pc = board[from];
386 Bitboard fromTo = from | to;
387 byTypeBB[ALL_PIECES] ^= fromTo;
388 byTypeBB[type_of(pc)] ^= fromTo;
389 byColorBB[color_of(pc)] ^= fromTo;
390 board[from] = NO_PIECE;
394 inline void Position::do_move(Move m, StateInfo& newSt) {
395 do_move(m, newSt, gives_check(m));
398 inline StateInfo* Position::state() const {
403 } // namespace Stockfish
405 #endif // #ifndef POSITION_H_INCLUDED