2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
5 Copyright (C) 2015-2020 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
7 Stockfish is free software: you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation, either version 3 of the License, or
10 (at your option) any later version.
12 Stockfish is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with this program. If not, see <http://www.gnu.org/licenses/>.
21 #ifndef POSITION_H_INCLUDED
22 #define POSITION_H_INCLUDED
26 #include <memory> // For std::unique_ptr
33 /// StateInfo struct stores information needed to restore a Position object to
34 /// its previous state when we retract a move. Whenever a move is made on the
35 /// board (by calling Position::do_move), a StateInfo object must be passed.
39 // Copied when making a move
42 Value nonPawnMaterial[COLOR_NB];
48 // 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 /// A list to keep track of the position states along the setup moves (from the
61 /// start position to the position just before the search starts). Needed by
62 /// 'draw by repetition' detection. Use a std::deque because pointers to
63 /// elements are not invalidated upon list resizing.
64 typedef std::unique_ptr<std::deque<StateInfo>> StateListPtr;
67 /// Position class stores information regarding the board representation as
68 /// pieces, side to move, hash keys, castling info, etc. Important methods are
69 /// do_move() and undo_move(), used by the search to update node info when
70 /// traversing the search tree.
78 Position(const Position&) = delete;
79 Position& operator=(const Position&) = delete;
81 // FEN string input/output
82 Position& set(const std::string& fenStr, bool isChess960, StateInfo* si, Thread* th);
83 Position& set(const std::string& code, Color c, StateInfo* si);
84 const std::string fen() const;
86 // Position representation
87 Bitboard pieces(PieceType pt) const;
88 Bitboard pieces(PieceType pt1, PieceType pt2) const;
89 Bitboard pieces(Color c) const;
90 Bitboard pieces(Color c, PieceType pt) const;
91 Bitboard pieces(Color c, PieceType pt1, PieceType pt2) const;
92 Piece piece_on(Square s) const;
93 Square ep_square() const;
94 bool empty(Square s) const;
95 template<PieceType Pt> int count(Color c) const;
96 template<PieceType Pt> int count() const;
97 template<PieceType Pt> const Square* squares(Color c) const;
98 template<PieceType Pt> Square square(Color c) const;
99 bool is_on_semiopen_file(Color c, Square s) const;
102 CastlingRights castling_rights(Color c) const;
103 bool can_castle(CastlingRights cr) const;
104 bool castling_impeded(CastlingRights cr) const;
105 Square castling_rook_square(CastlingRights cr) const;
108 Bitboard checkers() const;
109 Bitboard blockers_for_king(Color c) const;
110 Bitboard check_squares(PieceType pt) const;
111 bool is_discovery_check_on_king(Color c, Move m) const;
113 // Attacks to/from a given square
114 Bitboard attackers_to(Square s) const;
115 Bitboard attackers_to(Square s, Bitboard occupied) const;
116 Bitboard slider_blockers(Bitboard sliders, Square s, Bitboard& pinners) const;
118 // Properties of moves
119 bool legal(Move m) const;
120 bool pseudo_legal(const Move m) const;
121 bool capture(Move m) const;
122 bool capture_or_promotion(Move m) const;
123 bool gives_check(Move m) const;
124 bool advanced_pawn_push(Move m) const;
125 Piece moved_piece(Move m) const;
126 Piece captured_piece() const;
129 bool pawn_passed(Color c, Square s) const;
130 bool opposite_bishops() const;
131 int pawns_on_same_color_squares(Color c, Square s) const;
133 // Doing and undoing moves
134 void do_move(Move m, StateInfo& newSt);
135 void do_move(Move m, StateInfo& newSt, bool givesCheck);
136 void undo_move(Move m);
137 void do_null_move(StateInfo& newSt);
138 void undo_null_move();
140 // Static Exchange Evaluation
141 bool see_ge(Move m, Value threshold = VALUE_ZERO) const;
143 // Accessing hash keys
145 Key key_after(Move m) const;
146 Key material_key() const;
147 Key pawn_key() const;
149 // Other properties of the position
150 Color side_to_move() const;
151 int game_ply() const;
152 bool is_chess960() const;
153 Thread* this_thread() const;
154 bool is_draw(int ply) const;
155 bool has_game_cycle(int ply) const;
156 bool has_repeated() const;
157 int rule50_count() const;
158 Score psq_score() 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 // Initialization helpers (used while setting up a position)
168 void set_castling_right(Color c, Square rfrom);
169 void set_state(StateInfo* si) const;
170 void set_check_info(StateInfo* si) const;
173 void put_piece(Piece pc, Square s);
174 void remove_piece(Square s);
175 void move_piece(Square from, Square to);
177 void do_castling(Color us, Square from, Square& to, Square& rfrom, Square& rto);
180 Piece board[SQUARE_NB];
181 Bitboard byTypeBB[PIECE_TYPE_NB];
182 Bitboard byColorBB[COLOR_NB];
183 int pieceCount[PIECE_NB];
184 Square pieceList[PIECE_NB][16];
185 int index[SQUARE_NB];
186 int castlingRightsMask[SQUARE_NB];
187 Square castlingRookSquare[CASTLING_RIGHT_NB];
188 Bitboard castlingPath[CASTLING_RIGHT_NB];
198 extern Score psq[PIECE_NB][SQUARE_NB];
201 extern std::ostream& operator<<(std::ostream& os, const Position& pos);
203 inline Color Position::side_to_move() const {
207 inline Piece Position::piece_on(Square s) const {
212 inline bool Position::empty(Square s) const {
213 return piece_on(s) == NO_PIECE;
216 inline Piece Position::moved_piece(Move m) const {
217 return piece_on(from_sq(m));
220 inline Bitboard Position::pieces(PieceType pt = ALL_PIECES) const {
224 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2) const {
225 return pieces(pt1) | pieces(pt2);
228 inline Bitboard Position::pieces(Color c) const {
232 inline Bitboard Position::pieces(Color c, PieceType pt) const {
233 return pieces(c) & pieces(pt);
236 inline Bitboard Position::pieces(Color c, PieceType pt1, PieceType pt2) const {
237 return pieces(c) & (pieces(pt1) | pieces(pt2));
240 template<PieceType Pt> inline int Position::count(Color c) const {
241 return pieceCount[make_piece(c, Pt)];
244 template<PieceType Pt> inline int Position::count() const {
245 return count<Pt>(WHITE) + count<Pt>(BLACK);
248 template<PieceType Pt> inline const Square* Position::squares(Color c) const {
249 return pieceList[make_piece(c, Pt)];
252 template<PieceType Pt> inline Square Position::square(Color c) const {
253 assert(pieceCount[make_piece(c, Pt)] == 1);
254 return squares<Pt>(c)[0];
257 inline Square Position::ep_square() const {
261 inline bool Position::is_on_semiopen_file(Color c, Square s) const {
262 return !(pieces(c, PAWN) & file_bb(s));
265 inline bool Position::can_castle(CastlingRights cr) const {
266 return st->castlingRights & cr;
269 inline CastlingRights Position::castling_rights(Color c) const {
270 return c & CastlingRights(st->castlingRights);
273 inline bool Position::castling_impeded(CastlingRights cr) const {
274 assert(cr == WHITE_OO || cr == WHITE_OOO || cr == BLACK_OO || cr == BLACK_OOO);
276 return pieces() & castlingPath[cr];
279 inline Square Position::castling_rook_square(CastlingRights cr) const {
280 assert(cr == WHITE_OO || cr == WHITE_OOO || cr == BLACK_OO || cr == BLACK_OOO);
282 return castlingRookSquare[cr];
285 inline Bitboard Position::attackers_to(Square s) const {
286 return attackers_to(s, 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::check_squares(PieceType pt) const {
298 return st->checkSquares[pt];
301 inline bool Position::is_discovery_check_on_king(Color c, Move m) const {
302 return st->blockersForKing[c] & from_sq(m);
305 inline bool Position::pawn_passed(Color c, Square s) const {
306 return !(pieces(~c, PAWN) & passed_pawn_span(c, s));
309 inline bool Position::advanced_pawn_push(Move m) const {
310 return type_of(moved_piece(m)) == PAWN
311 && relative_rank(sideToMove, to_sq(m)) > RANK_5;
314 inline int Position::pawns_on_same_color_squares(Color c, Square s) const {
315 return popcount(pieces(c, PAWN) & ((DarkSquares & s) ? DarkSquares : ~DarkSquares));
318 inline Key Position::key() const {
322 inline Key Position::pawn_key() const {
326 inline Key Position::material_key() const {
327 return st->materialKey;
330 inline Score Position::psq_score() const {
334 inline Value Position::non_pawn_material(Color c) const {
335 return st->nonPawnMaterial[c];
338 inline Value Position::non_pawn_material() const {
339 return non_pawn_material(WHITE) + non_pawn_material(BLACK);
342 inline int Position::game_ply() const {
346 inline int Position::rule50_count() const {
350 inline bool Position::opposite_bishops() const {
351 return count<BISHOP>(WHITE) == 1
352 && count<BISHOP>(BLACK) == 1
353 && opposite_colors(square<BISHOP>(WHITE), square<BISHOP>(BLACK));
356 inline bool Position::is_chess960() const {
360 inline bool Position::capture_or_promotion(Move m) const {
362 return type_of(m) != NORMAL ? type_of(m) != CASTLING : !empty(to_sq(m));
365 inline bool Position::capture(Move m) const {
367 // Castling is encoded as "king captures rook"
368 return (!empty(to_sq(m)) && type_of(m) != CASTLING) || type_of(m) == ENPASSANT;
371 inline Piece Position::captured_piece() const {
372 return st->capturedPiece;
375 inline Thread* Position::this_thread() const {
379 inline void Position::put_piece(Piece pc, Square s) {
382 byTypeBB[ALL_PIECES] |= byTypeBB[type_of(pc)] |= s;
383 byColorBB[color_of(pc)] |= s;
384 index[s] = pieceCount[pc]++;
385 pieceList[pc][index[s]] = s;
386 pieceCount[make_piece(color_of(pc), ALL_PIECES)]++;
387 psq += PSQT::psq[pc][s];
390 inline void Position::remove_piece(Square s) {
392 // WARNING: This is not a reversible operation. If we remove a piece in
393 // do_move() and then replace it in undo_move() we will put it at the end of
394 // the list and not in its original place, it means index[] and pieceList[]
395 // are not invariant to a do_move() + undo_move() sequence.
397 byTypeBB[ALL_PIECES] ^= s;
398 byTypeBB[type_of(pc)] ^= s;
399 byColorBB[color_of(pc)] ^= s;
400 /* board[s] = NO_PIECE; Not needed, overwritten by the capturing one */
401 Square lastSquare = pieceList[pc][--pieceCount[pc]];
402 index[lastSquare] = index[s];
403 pieceList[pc][index[lastSquare]] = lastSquare;
404 pieceList[pc][pieceCount[pc]] = SQ_NONE;
405 pieceCount[make_piece(color_of(pc), ALL_PIECES)]--;
406 psq -= PSQT::psq[pc][s];
409 inline void Position::move_piece(Square from, Square to) {
411 // index[from] is not updated and becomes stale. This works as long as index[]
412 // is accessed just by known occupied squares.
413 Piece pc = board[from];
414 Bitboard fromTo = from | to;
415 byTypeBB[ALL_PIECES] ^= fromTo;
416 byTypeBB[type_of(pc)] ^= fromTo;
417 byColorBB[color_of(pc)] ^= fromTo;
418 board[from] = NO_PIECE;
420 index[to] = index[from];
421 pieceList[pc][index[to]] = to;
422 psq += PSQT::psq[pc][to] - PSQT::psq[pc][from];
425 inline void Position::do_move(Move m, StateInfo& newSt) {
426 do_move(m, newSt, gives_check(m));
429 #endif // #ifndef POSITION_H_INCLUDED