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
32 #include "nnue/nnue_accumulator.h"
36 /// StateInfo struct stores information needed to restore a Position object to
37 /// its previous state when we retract a move. Whenever a move is made on the
38 /// board (by calling Position::do_move), a StateInfo object must be passed.
42 // Copied when making a move
44 Value nonPawnMaterial[COLOR_NB];
50 // Not copied when making a move (will be recomputed anyhow)
54 Bitboard blockersForKing[COLOR_NB];
55 Bitboard pinners[COLOR_NB];
56 Bitboard checkSquares[PIECE_TYPE_NB];
61 Eval::NNUE::Accumulator accumulator;
62 DirtyPiece dirtyPiece;
66 /// A list to keep track of the position states along the setup moves (from the
67 /// start position to the position just before the search starts). Needed by
68 /// 'draw by repetition' detection. Use a std::deque because pointers to
69 /// elements are not invalidated upon list resizing.
70 using StateListPtr = std::unique_ptr<std::deque<StateInfo>>;
73 /// Position class stores information regarding the board representation as
74 /// pieces, side to move, hash keys, castling info, etc. Important methods are
75 /// do_move() and undo_move(), used by the search to update node info when
76 /// traversing the search tree.
84 Position(const Position&) = delete;
85 Position& operator=(const Position&) = delete;
87 // FEN string input/output
88 Position& set(const std::string& fenStr, bool isChess960, StateInfo* si, Thread* th);
89 Position& set(const std::string& code, Color c, StateInfo* si);
90 std::string fen() const;
92 // Position representation
93 Bitboard pieces(PieceType pt = ALL_PIECES) const;
94 template<typename ...PieceTypes> Bitboard pieces(PieceType pt, PieceTypes... pts) const;
95 Bitboard pieces(Color c) const;
96 template<typename ...PieceTypes> 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> int count(Color c) const;
101 template<PieceType Pt> int count() const;
102 template<PieceType Pt> Square square(Color c) const;
105 CastlingRights castling_rights(Color c) const;
106 bool can_castle(CastlingRights cr) const;
107 bool castling_impeded(CastlingRights cr) const;
108 Square castling_rook_square(CastlingRights cr) const;
111 Bitboard checkers() const;
112 Bitboard blockers_for_king(Color c) const;
113 Bitboard check_squares(PieceType pt) const;
114 Bitboard pinners(Color c) const;
116 // Attacks to/from a given square
117 Bitboard attackers_to(Square s) const;
118 Bitboard attackers_to(Square s, Bitboard occupied) const;
119 Bitboard slider_blockers(Bitboard sliders, Square s, Bitboard& pinners) const;
120 template<PieceType Pt> Bitboard attacks_by(Color c) const;
122 // Properties of moves
123 bool legal(Move m) const;
124 bool pseudo_legal(const Move m) const;
125 bool capture(Move m) const;
126 bool capture_stage(Move m) const;
127 bool gives_check(Move m) const;
128 Piece moved_piece(Move m) const;
129 Piece captured_piece() const;
131 // Doing and undoing moves
132 void do_move(Move m, StateInfo& newSt);
133 void do_move(Move m, StateInfo& newSt, bool givesCheck);
134 void undo_move(Move m);
135 void do_null_move(StateInfo& newSt);
136 void undo_null_move();
138 // Static Exchange Evaluation
139 bool see_ge(Move m, Value threshold = VALUE_ZERO) const;
140 bool see_ge(Move m, Bitboard& occupied, Value threshold = VALUE_ZERO) const;
142 // Accessing hash keys
144 Key key_after(Move m) const;
145 Key material_key() const;
147 // Other properties of the position
148 Color side_to_move() const;
149 int game_ply() const;
150 bool is_chess960() const;
151 Thread* this_thread() const;
152 bool is_draw(int ply) const;
153 bool has_game_cycle(int ply) const;
154 bool has_repeated() const;
155 int rule50_count() const;
156 Value psq_eg_stm() const;
157 Value non_pawn_material(Color c) const;
158 Value non_pawn_material() const;
160 // Position consistency check, for debugging
161 bool pos_is_ok() const;
165 StateInfo* state() const;
167 void put_piece(Piece pc, Square s);
168 void remove_piece(Square s);
171 // Initialization helpers (used while setting up a position)
172 void set_castling_right(Color c, Square rfrom);
173 void set_state() const;
174 void set_check_info() const;
177 void move_piece(Square from, Square to);
179 void do_castling(Color us, Square from, Square& to, Square& rfrom, Square& rto);
180 template<bool AfterMove>
181 Key adjust_key50(Key k) const;
184 Piece board[SQUARE_NB];
185 Bitboard byTypeBB[PIECE_TYPE_NB];
186 Bitboard byColorBB[COLOR_NB];
187 int pieceCount[PIECE_NB];
188 int castlingRightsMask[SQUARE_NB];
189 Square castlingRookSquare[CASTLING_RIGHT_NB];
190 Bitboard castlingPath[CASTLING_RIGHT_NB];
199 std::ostream& operator<<(std::ostream& os, const Position& pos);
201 inline Color Position::side_to_move() const {
205 inline Piece Position::piece_on(Square s) const {
210 inline bool Position::empty(Square s) const {
211 return piece_on(s) == NO_PIECE;
214 inline Piece Position::moved_piece(Move m) const {
215 return piece_on(from_sq(m));
218 inline Bitboard Position::pieces(PieceType pt) const {
222 template<typename ...PieceTypes>
223 inline Bitboard Position::pieces(PieceType pt, PieceTypes... pts) const {
224 return pieces(pt) | pieces(pts...);
227 inline Bitboard Position::pieces(Color c) const {
231 template<typename ...PieceTypes>
232 inline Bitboard Position::pieces(Color c, PieceTypes... pts) const {
233 return pieces(c) & pieces(pts...);
236 template<PieceType Pt> inline int Position::count(Color c) const {
237 return pieceCount[make_piece(c, Pt)];
240 template<PieceType Pt> inline int Position::count() const {
241 return count<Pt>(WHITE) + count<Pt>(BLACK);
244 template<PieceType Pt> inline Square Position::square(Color c) const {
245 assert(count<Pt>(c) == 1);
246 return lsb(pieces(c, Pt));
249 inline Square Position::ep_square() const {
253 inline bool Position::can_castle(CastlingRights cr) const {
254 return st->castlingRights & cr;
257 inline CastlingRights Position::castling_rights(Color c) const {
258 return c & CastlingRights(st->castlingRights);
261 inline bool Position::castling_impeded(CastlingRights cr) const {
262 assert(cr == WHITE_OO || cr == WHITE_OOO || cr == BLACK_OO || cr == BLACK_OOO);
264 return pieces() & castlingPath[cr];
267 inline Square Position::castling_rook_square(CastlingRights cr) const {
268 assert(cr == WHITE_OO || cr == WHITE_OOO || cr == BLACK_OO || cr == BLACK_OOO);
270 return castlingRookSquare[cr];
273 inline Bitboard Position::attackers_to(Square s) const {
274 return attackers_to(s, pieces());
277 template<PieceType Pt>
278 inline Bitboard Position::attacks_by(Color c) const {
280 if constexpr (Pt == PAWN)
281 return c == WHITE ? pawn_attacks_bb<WHITE>(pieces(WHITE, PAWN))
282 : pawn_attacks_bb<BLACK>(pieces(BLACK, PAWN));
285 Bitboard threats = 0;
286 Bitboard attackers = pieces(c, Pt);
288 threats |= attacks_bb<Pt>(pop_lsb(attackers), pieces());
293 inline Bitboard Position::checkers() const {
294 return st->checkersBB;
297 inline Bitboard Position::blockers_for_king(Color c) const {
298 return st->blockersForKing[c];
301 inline Bitboard Position::pinners(Color c) const {
302 return st->pinners[c];
305 inline Bitboard Position::check_squares(PieceType pt) const {
306 return st->checkSquares[pt];
309 inline Key Position::key() const {
310 return adjust_key50<false>(st->key);
313 template<bool AfterMove>
314 inline Key Position::adjust_key50(Key k) const
316 return st->rule50 < 14 - AfterMove
317 ? k : k ^ make_key((st->rule50 - (14 - AfterMove)) / 8);
320 inline Key Position::material_key() const {
321 return st->materialKey;
324 inline Value Position::psq_eg_stm() const {
325 return (sideToMove == WHITE ? 1 : -1) * eg_value(psq);
328 inline Value Position::non_pawn_material(Color c) const {
329 return st->nonPawnMaterial[c];
332 inline Value Position::non_pawn_material() const {
333 return non_pawn_material(WHITE) + non_pawn_material(BLACK);
336 inline int Position::game_ply() const {
340 inline int Position::rule50_count() const {
344 inline bool Position::is_chess960() const {
348 inline bool Position::capture(Move m) const {
350 return (!empty(to_sq(m)) && type_of(m) != CASTLING)
351 || type_of(m) == EN_PASSANT;
354 // returns true if a move is generated from the capture stage
355 // having also queen promotions covered, i.e. consistency with the capture stage move generation
356 // is needed to avoid the generation of duplicate moves.
357 inline bool Position::capture_stage(Move m) const {
359 return capture(m) || promotion_type(m) == QUEEN;
362 inline Piece Position::captured_piece() const {
363 return st->capturedPiece;
366 inline Thread* Position::this_thread() const {
370 inline void Position::put_piece(Piece pc, Square s) {
373 byTypeBB[ALL_PIECES] |= byTypeBB[type_of(pc)] |= s;
374 byColorBB[color_of(pc)] |= s;
376 pieceCount[make_piece(color_of(pc), ALL_PIECES)]++;
377 psq += PSQT::psq[pc][s];
380 inline void Position::remove_piece(Square s) {
383 byTypeBB[ALL_PIECES] ^= s;
384 byTypeBB[type_of(pc)] ^= s;
385 byColorBB[color_of(pc)] ^= s;
388 pieceCount[make_piece(color_of(pc), ALL_PIECES)]--;
389 psq -= PSQT::psq[pc][s];
392 inline void Position::move_piece(Square from, Square to) {
394 Piece pc = board[from];
395 Bitboard fromTo = from | to;
396 byTypeBB[ALL_PIECES] ^= fromTo;
397 byTypeBB[type_of(pc)] ^= fromTo;
398 byColorBB[color_of(pc)] ^= fromTo;
399 board[from] = NO_PIECE;
401 psq += PSQT::psq[pc][to] - PSQT::psq[pc][from];
404 inline void Position::do_move(Move m, StateInfo& newSt) {
405 do_move(m, newSt, gives_check(m));
408 inline StateInfo* Position::state() const {
413 } // namespace Stockfish
415 #endif // #ifndef POSITION_H_INCLUDED