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];
59 /// A list to keep track of the position states along the setup moves (from the
60 /// start position to the position just before the search starts). Needed by
61 /// 'draw by repetition' detection. Use a std::deque because pointers to
62 /// elements are not invalidated upon list resizing.
63 typedef std::unique_ptr<std::deque<StateInfo>> StateListPtr;
66 /// Position class stores information regarding the board representation as
67 /// pieces, side to move, hash keys, castling info, etc. Important methods are
68 /// do_move() and undo_move(), used by the search to update node info when
69 /// traversing the search tree.
77 Position(const Position&) = delete;
78 Position& operator=(const Position&) = delete;
80 // FEN string input/output
81 Position& set(const std::string& fenStr, bool isChess960, StateInfo* si, Thread* th);
82 Position& set(const std::string& code, Color c, StateInfo* si);
83 const std::string fen() const;
85 // Position representation
86 Bitboard pieces(PieceType pt) const;
87 Bitboard pieces(PieceType pt1, PieceType pt2) const;
88 Bitboard pieces(Color c) const;
89 Bitboard pieces(Color c, PieceType pt) const;
90 Bitboard pieces(Color c, PieceType pt1, PieceType pt2) const;
91 Piece piece_on(Square s) const;
92 Square ep_square() const;
93 bool empty(Square s) const;
94 template<PieceType Pt> int count(Color c) const;
95 template<PieceType Pt> int count() const;
96 template<PieceType Pt> const Square* squares(Color c) const;
97 template<PieceType Pt> Square square(Color c) const;
98 bool is_on_semiopen_file(Color c, Square s) const;
101 int castling_rights(Color c) const;
102 bool can_castle(CastlingRights cr) const;
103 bool castling_impeded(CastlingRights cr) const;
104 Square castling_rook_square(CastlingRights cr) const;
107 Bitboard checkers() const;
108 Bitboard blockers_for_king(Color c) const;
109 Bitboard check_squares(PieceType pt) const;
110 bool is_discovery_check_on_king(Color c, Move m) const;
112 // Attacks to/from a given square
113 Bitboard attackers_to(Square s) const;
114 Bitboard attackers_to(Square s, Bitboard occupied) const;
115 Bitboard attacks_from(PieceType pt, Square s) const;
116 template<PieceType> Bitboard attacks_from(Square s) const;
117 template<PieceType> Bitboard attacks_from(Square s, Color c) const;
118 Bitboard slider_blockers(Bitboard sliders, Square s, Bitboard& pinners) 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_or_promotion(Move m) const;
125 bool gives_check(Move m) const;
126 bool advanced_pawn_push(Move m) const;
127 Piece moved_piece(Move m) const;
128 Piece captured_piece() const;
131 bool pawn_passed(Color c, Square s) const;
132 bool opposite_bishops() const;
133 int pawns_on_same_color_squares(Color c, Square s) 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;
149 Key pawn_key() const;
151 // Other properties of the position
152 Color side_to_move() const;
153 int game_ply() const;
154 bool is_chess960() const;
155 Thread* this_thread() const;
156 bool is_draw(int ply) const;
157 bool has_game_cycle(int ply) const;
158 bool has_repeated() const;
159 int rule50_count() const;
160 Score psq_score() const;
161 Value non_pawn_material(Color c) const;
162 Value non_pawn_material() const;
164 // Position consistency check, for debugging
165 bool pos_is_ok() const;
169 // Initialization helpers (used while setting up a position)
170 void set_castling_right(Color c, Square rfrom);
171 void set_state(StateInfo* si) const;
172 void set_check_info(StateInfo* si) const;
175 void put_piece(Piece pc, Square s);
176 void remove_piece(Square s);
177 void move_piece(Square from, Square to);
179 void do_castling(Color us, Square from, Square& to, Square& rfrom, Square& rto);
182 Piece board[SQUARE_NB];
183 Bitboard byTypeBB[PIECE_TYPE_NB];
184 Bitboard byColorBB[COLOR_NB];
185 int pieceCount[PIECE_NB];
186 Square pieceList[PIECE_NB][16];
187 int index[SQUARE_NB];
188 int castlingRightsMask[SQUARE_NB];
189 Square castlingRookSquare[CASTLING_RIGHT_NB];
190 Bitboard castlingPath[CASTLING_RIGHT_NB];
200 extern Score psq[PIECE_NB][SQUARE_NB];
203 extern std::ostream& operator<<(std::ostream& os, const Position& pos);
205 inline Color Position::side_to_move() const {
209 inline Piece Position::piece_on(Square s) const {
214 inline bool Position::empty(Square s) const {
215 return piece_on(s) == NO_PIECE;
218 inline Piece Position::moved_piece(Move m) const {
219 return piece_on(from_sq(m));
222 inline Bitboard Position::pieces(PieceType pt = ALL_PIECES) const {
226 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2) const {
227 return pieces(pt1) | pieces(pt2);
230 inline Bitboard Position::pieces(Color c) const {
234 inline Bitboard Position::pieces(Color c, PieceType pt) const {
235 return pieces(c) & pieces(pt);
238 inline Bitboard Position::pieces(Color c, PieceType pt1, PieceType pt2) const {
239 return pieces(c) & (pieces(pt1) | pieces(pt2));
242 template<PieceType Pt> inline int Position::count(Color c) const {
243 return pieceCount[make_piece(c, Pt)];
246 template<PieceType Pt> inline int Position::count() const {
247 return count<Pt>(WHITE) + count<Pt>(BLACK);
250 template<PieceType Pt> inline const Square* Position::squares(Color c) const {
251 return pieceList[make_piece(c, Pt)];
254 template<PieceType Pt> inline Square Position::square(Color c) const {
255 assert(pieceCount[make_piece(c, Pt)] == 1);
256 return squares<Pt>(c)[0];
259 inline Square Position::ep_square() const {
263 inline bool Position::is_on_semiopen_file(Color c, Square s) const {
264 return !(pieces(c, PAWN) & file_bb(s));
267 inline bool Position::can_castle(CastlingRights cr) const {
268 return st->castlingRights & cr;
271 inline int Position::castling_rights(Color c) const {
272 return st->castlingRights & (c == WHITE ? WHITE_CASTLING : BLACK_CASTLING);
275 inline bool Position::castling_impeded(CastlingRights cr) const {
276 assert(cr == WHITE_OO || cr == WHITE_OOO || cr == BLACK_OO || cr == BLACK_OOO);
278 return pieces() & castlingPath[cr];
281 inline Square Position::castling_rook_square(CastlingRights cr) const {
282 assert(cr == WHITE_OO || cr == WHITE_OOO || cr == BLACK_OO || cr == BLACK_OOO);
284 return castlingRookSquare[cr];
287 template<PieceType Pt>
288 inline Bitboard Position::attacks_from(Square s) const {
289 static_assert(Pt != PAWN, "Pawn attacks need color");
291 return Pt == BISHOP || Pt == ROOK ? attacks_bb<Pt>(s, pieces())
292 : Pt == QUEEN ? attacks_from<ROOK>(s) | attacks_from<BISHOP>(s)
293 : PseudoAttacks[Pt][s];
297 inline Bitboard Position::attacks_from<PAWN>(Square s, Color c) const {
298 return PawnAttacks[c][s];
301 inline Bitboard Position::attacks_from(PieceType pt, Square s) const {
302 return attacks_bb(pt, s, pieces());
305 inline Bitboard Position::attackers_to(Square s) const {
306 return attackers_to(s, pieces());
309 inline Bitboard Position::checkers() const {
310 return st->checkersBB;
313 inline Bitboard Position::blockers_for_king(Color c) const {
314 return st->blockersForKing[c];
317 inline Bitboard Position::check_squares(PieceType pt) const {
318 return st->checkSquares[pt];
321 inline bool Position::is_discovery_check_on_king(Color c, Move m) const {
322 return st->blockersForKing[c] & from_sq(m);
325 inline bool Position::pawn_passed(Color c, Square s) const {
326 return !(pieces(~c, PAWN) & passed_pawn_span(c, s));
329 inline bool Position::advanced_pawn_push(Move m) const {
330 return type_of(moved_piece(m)) == PAWN
331 && relative_rank(sideToMove, to_sq(m)) > RANK_5;
334 inline int Position::pawns_on_same_color_squares(Color c, Square s) const {
335 return popcount(pieces(c, PAWN) & ((DarkSquares & s) ? DarkSquares : ~DarkSquares));
338 inline Key Position::key() const {
342 inline Key Position::pawn_key() const {
346 inline Key Position::material_key() const {
347 return st->materialKey;
350 inline Score Position::psq_score() const {
354 inline Value Position::non_pawn_material(Color c) const {
355 return st->nonPawnMaterial[c];
358 inline Value Position::non_pawn_material() const {
359 return non_pawn_material(WHITE) + non_pawn_material(BLACK);
362 inline int Position::game_ply() const {
366 inline int Position::rule50_count() const {
370 inline bool Position::opposite_bishops() const {
371 return count<BISHOP>(WHITE) == 1
372 && count<BISHOP>(BLACK) == 1
373 && opposite_colors(square<BISHOP>(WHITE), square<BISHOP>(BLACK));
376 inline bool Position::is_chess960() const {
380 inline bool Position::capture_or_promotion(Move m) const {
382 return type_of(m) != NORMAL ? type_of(m) != CASTLING : !empty(to_sq(m));
385 inline bool Position::capture(Move m) const {
387 // Castling is encoded as "king captures rook"
388 return (!empty(to_sq(m)) && type_of(m) != CASTLING) || type_of(m) == ENPASSANT;
391 inline Piece Position::captured_piece() const {
392 return st->capturedPiece;
395 inline Thread* Position::this_thread() const {
399 inline void Position::put_piece(Piece pc, Square s) {
402 byTypeBB[ALL_PIECES] |= s;
403 byTypeBB[type_of(pc)] |= s;
404 byColorBB[color_of(pc)] |= s;
405 index[s] = pieceCount[pc]++;
406 pieceList[pc][index[s]] = s;
407 pieceCount[make_piece(color_of(pc), ALL_PIECES)]++;
408 psq += PSQT::psq[pc][s];
411 inline void Position::remove_piece(Square s) {
413 // WARNING: This is not a reversible operation. If we remove a piece in
414 // do_move() and then replace it in undo_move() we will put it at the end of
415 // the list and not in its original place, it means index[] and pieceList[]
416 // are not invariant to a do_move() + undo_move() sequence.
418 byTypeBB[ALL_PIECES] ^= s;
419 byTypeBB[type_of(pc)] ^= s;
420 byColorBB[color_of(pc)] ^= s;
421 /* board[s] = NO_PIECE; Not needed, overwritten by the capturing one */
422 Square lastSquare = pieceList[pc][--pieceCount[pc]];
423 index[lastSquare] = index[s];
424 pieceList[pc][index[lastSquare]] = lastSquare;
425 pieceList[pc][pieceCount[pc]] = SQ_NONE;
426 pieceCount[make_piece(color_of(pc), ALL_PIECES)]--;
427 psq -= PSQT::psq[pc][s];
430 inline void Position::move_piece(Square from, Square to) {
432 // index[from] is not updated and becomes stale. This works as long as index[]
433 // is accessed just by known occupied squares.
434 Piece pc = board[from];
435 Bitboard fromTo = from | to;
436 byTypeBB[ALL_PIECES] ^= fromTo;
437 byTypeBB[type_of(pc)] ^= fromTo;
438 byColorBB[color_of(pc)] ^= fromTo;
439 board[from] = NO_PIECE;
441 index[to] = index[from];
442 pieceList[pc][index[to]] = to;
443 psq += PSQT::psq[pc][to] - PSQT::psq[pc][from];
446 inline void Position::do_move(Move m, StateInfo& newSt) {
447 do_move(m, newSt, gives_check(m));
450 #endif // #ifndef POSITION_H_INCLUDED