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
6 Stockfish is free software: you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation, either version 3 of the License, or
9 (at your option) any later version.
11 Stockfish is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with this program. If not, see <http://www.gnu.org/licenses/>.
20 #ifndef POSITION_H_INCLUDED
21 #define POSITION_H_INCLUDED
24 #include <cstddef> // For offsetof()
33 /// CheckInfo struct is initialized at c'tor time and keeps info used to detect
34 /// if a move gives check.
38 explicit CheckInfo(const Position&);
40 Bitboard dcCandidates;
42 Bitboard checkSq[PIECE_TYPE_NB];
47 /// StateInfo struct stores information needed to restore a Position object to
48 /// its previous state when we retract a move. Whenever a move is made on the
49 /// board (by calling Position::do_move), a StateInfo object must be passed.
53 // Copied when making a move
56 Value nonPawnMaterial[COLOR_NB];
63 // Not copied when making a move
66 PieceType capturedType;
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.
78 friend std::ostream& operator<<(std::ostream&, const Position&);
83 Position() = default; // To define the global object RootPos
84 Position(const Position&) = delete;
85 Position(const Position& pos, Thread* th) { *this = pos; thisThread = th; }
86 Position(const std::string& f, bool c960, Thread* th) { set(f, c960, th); }
87 Position& operator=(const Position&); // To assign RootPos from UCI
89 // FEN string input/output
90 void set(const std::string& fenStr, bool isChess960, Thread* th);
91 const std::string fen() const;
93 // Position representation
94 Bitboard pieces() const;
95 Bitboard pieces(PieceType pt) const;
96 Bitboard pieces(PieceType pt1, PieceType pt2) const;
97 Bitboard pieces(Color c) const;
98 Bitboard pieces(Color c, PieceType pt) const;
99 Bitboard pieces(Color c, PieceType pt1, PieceType pt2) const;
100 Piece piece_on(Square s) const;
101 Square king_square(Color c) const;
102 Square ep_square() const;
103 bool empty(Square s) const;
104 template<PieceType Pt> int count(Color c) const;
105 template<PieceType Pt> const Square* list(Color c) const;
108 int can_castle(Color c) const;
109 int can_castle(CastlingRight cr) const;
110 bool castling_impeded(CastlingRight cr) const;
111 Square castling_rook_square(CastlingRight cr) const;
114 Bitboard checkers() const;
115 Bitboard discovered_check_candidates() const;
116 Bitboard pinned_pieces(Color c) const;
118 // Attacks to/from a given square
119 Bitboard attackers_to(Square s) const;
120 Bitboard attackers_to(Square s, Bitboard occupied) const;
121 Bitboard attacks_from(Piece pc, Square s) const;
122 template<PieceType> Bitboard attacks_from(Square s) const;
123 template<PieceType> Bitboard attacks_from(Square s, Color c) const;
125 // Properties of moves
126 bool legal(Move m, Bitboard pinned) const;
127 bool pseudo_legal(const Move m) const;
128 bool capture(Move m) const;
129 bool capture_or_promotion(Move m) const;
130 bool gives_check(Move m, const CheckInfo& ci) const;
131 bool advanced_pawn_push(Move m) const;
132 Piece moved_piece(Move m) const;
133 PieceType captured_piece_type() const;
136 bool pawn_passed(Color c, Square s) const;
137 bool pawn_on_7th(Color c) const;
138 bool opposite_bishops() const;
140 // Doing and undoing moves
141 void do_move(Move m, StateInfo& st);
142 void do_move(Move m, StateInfo& st, const CheckInfo& ci, bool givesCheck);
143 void undo_move(Move m);
144 void do_null_move(StateInfo& st);
145 void undo_null_move();
147 // Static exchange evaluation
148 Value see(Move m) const;
149 Value see_sign(Move m) const;
151 // Accessing hash keys
153 Key key_after(Move m) const;
154 Key exclusion_key() const;
155 Key material_key() const;
156 Key pawn_key() const;
158 // Other properties of the position
159 Color side_to_move() const;
160 Phase game_phase() const;
161 int game_ply() const;
162 bool is_chess960() const;
163 Thread* this_thread() const;
164 uint64_t nodes_searched() const;
165 void set_nodes_searched(uint64_t n);
166 bool is_draw() const;
167 int rule50_count() const;
168 Score psq_score() const;
169 Value non_pawn_material(Color c) const;
171 // Position consistency check, for debugging
172 bool pos_is_ok(int* failedStep = nullptr) const;
176 // Initialization helpers (used while setting up a position)
178 void set_castling_right(Color c, Square rfrom);
179 void set_state(StateInfo* si) const;
182 Bitboard check_blockers(Color c, Color kingColor) const;
183 void put_piece(Color c, PieceType pt, Square s);
184 void remove_piece(Color c, PieceType pt, Square s);
185 void move_piece(Color c, PieceType pt, Square from, Square to);
187 void do_castling(Color us, Square from, Square& to, Square& rfrom, Square& rto);
190 Piece board[SQUARE_NB];
191 Bitboard byTypeBB[PIECE_TYPE_NB];
192 Bitboard byColorBB[COLOR_NB];
193 int pieceCount[COLOR_NB][PIECE_TYPE_NB];
194 Square pieceList[COLOR_NB][PIECE_TYPE_NB][16];
195 int index[SQUARE_NB];
196 int castlingRightsMask[SQUARE_NB];
197 Square castlingRookSquare[CASTLING_RIGHT_NB];
198 Bitboard castlingPath[CASTLING_RIGHT_NB];
199 StateInfo startState;
208 inline Color Position::side_to_move() const {
212 inline bool Position::empty(Square s) const {
213 return board[s] == NO_PIECE;
216 inline Piece Position::piece_on(Square s) const {
220 inline Piece Position::moved_piece(Move m) const {
221 return board[from_sq(m)];
224 inline Bitboard Position::pieces() const {
225 return byTypeBB[ALL_PIECES];
228 inline Bitboard Position::pieces(PieceType pt) const {
232 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2) const {
233 return byTypeBB[pt1] | byTypeBB[pt2];
236 inline Bitboard Position::pieces(Color c) const {
240 inline Bitboard Position::pieces(Color c, PieceType pt) const {
241 return byColorBB[c] & byTypeBB[pt];
244 inline Bitboard Position::pieces(Color c, PieceType pt1, PieceType pt2) const {
245 return byColorBB[c] & (byTypeBB[pt1] | byTypeBB[pt2]);
248 template<PieceType Pt> inline int Position::count(Color c) const {
249 return pieceCount[c][Pt];
252 template<PieceType Pt> inline const Square* Position::list(Color c) const {
253 return pieceList[c][Pt];
256 inline Square Position::king_square(Color c) const {
257 return pieceList[c][KING][0];
260 inline Square Position::ep_square() const {
264 inline int Position::can_castle(CastlingRight cr) const {
265 return st->castlingRights & cr;
268 inline int Position::can_castle(Color c) const {
269 return st->castlingRights & ((WHITE_OO | WHITE_OOO) << (2 * c));
272 inline bool Position::castling_impeded(CastlingRight cr) const {
273 return byTypeBB[ALL_PIECES] & castlingPath[cr];
276 inline Square Position::castling_rook_square(CastlingRight cr) const {
277 return castlingRookSquare[cr];
280 template<PieceType Pt>
281 inline Bitboard Position::attacks_from(Square s) const {
282 return Pt == BISHOP || Pt == ROOK ? attacks_bb<Pt>(s, byTypeBB[ALL_PIECES])
283 : Pt == QUEEN ? attacks_from<ROOK>(s) | attacks_from<BISHOP>(s)
284 : StepAttacksBB[Pt][s];
288 inline Bitboard Position::attacks_from<PAWN>(Square s, Color c) const {
289 return StepAttacksBB[make_piece(c, PAWN)][s];
292 inline Bitboard Position::attacks_from(Piece pc, Square s) const {
293 return attacks_bb(pc, s, byTypeBB[ALL_PIECES]);
296 inline Bitboard Position::attackers_to(Square s) const {
297 return attackers_to(s, byTypeBB[ALL_PIECES]);
300 inline Bitboard Position::checkers() const {
301 return st->checkersBB;
304 inline Bitboard Position::discovered_check_candidates() const {
305 return check_blockers(sideToMove, ~sideToMove);
308 inline Bitboard Position::pinned_pieces(Color c) const {
309 return check_blockers(c, c);
312 inline bool Position::pawn_passed(Color c, Square s) const {
313 return !(pieces(~c, PAWN) & passed_pawn_mask(c, s));
316 inline bool Position::advanced_pawn_push(Move m) const {
317 return type_of(moved_piece(m)) == PAWN
318 && relative_rank(sideToMove, from_sq(m)) > RANK_4;
321 inline Key Position::key() const {
325 inline Key Position::pawn_key() const {
329 inline Key Position::material_key() const {
330 return st->materialKey;
333 inline Score Position::psq_score() const {
337 inline Value Position::non_pawn_material(Color c) const {
338 return st->nonPawnMaterial[c];
341 inline int Position::game_ply() const {
345 inline int Position::rule50_count() const {
349 inline uint64_t Position::nodes_searched() const {
353 inline void Position::set_nodes_searched(uint64_t n) {
357 inline bool Position::opposite_bishops() const {
358 return pieceCount[WHITE][BISHOP] == 1
359 && pieceCount[BLACK][BISHOP] == 1
360 && opposite_colors(pieceList[WHITE][BISHOP][0], pieceList[BLACK][BISHOP][0]);
363 inline bool Position::pawn_on_7th(Color c) const {
364 return pieces(c, PAWN) & rank_bb(relative_rank(c, RANK_7));
367 inline bool Position::is_chess960() const {
371 inline bool Position::capture_or_promotion(Move m) const {
374 return type_of(m) != NORMAL ? type_of(m) != CASTLING : !empty(to_sq(m));
377 inline bool Position::capture(Move m) const {
379 // Castling is encoded as "king captures the rook"
381 return (!empty(to_sq(m)) && type_of(m) != CASTLING) || type_of(m) == ENPASSANT;
384 inline PieceType Position::captured_piece_type() const {
385 return st->capturedType;
388 inline Thread* Position::this_thread() const {
392 inline void Position::put_piece(Color c, PieceType pt, Square s) {
394 board[s] = make_piece(c, pt);
395 byTypeBB[ALL_PIECES] |= s;
398 index[s] = pieceCount[c][pt]++;
399 pieceList[c][pt][index[s]] = s;
400 pieceCount[c][ALL_PIECES]++;
403 inline void Position::remove_piece(Color c, PieceType pt, Square s) {
405 // WARNING: This is not a reversible operation. If we remove a piece in
406 // do_move() and then replace it in undo_move() we will put it at the end of
407 // the list and not in its original place, it means index[] and pieceList[]
408 // are not guaranteed to be invariant to a do_move() + undo_move() sequence.
409 byTypeBB[ALL_PIECES] ^= s;
412 /* board[s] = NO_PIECE; Not needed, overwritten by the capturing one */
413 Square lastSquare = pieceList[c][pt][--pieceCount[c][pt]];
414 index[lastSquare] = index[s];
415 pieceList[c][pt][index[lastSquare]] = lastSquare;
416 pieceList[c][pt][pieceCount[c][pt]] = SQ_NONE;
417 pieceCount[c][ALL_PIECES]--;
420 inline void Position::move_piece(Color c, PieceType pt, Square from, Square to) {
422 // index[from] is not updated and becomes stale. This works as long as index[]
423 // is accessed just by known occupied squares.
424 Bitboard from_to_bb = SquareBB[from] ^ SquareBB[to];
425 byTypeBB[ALL_PIECES] ^= from_to_bb;
426 byTypeBB[pt] ^= from_to_bb;
427 byColorBB[c] ^= from_to_bb;
428 board[from] = NO_PIECE;
429 board[to] = make_piece(c, pt);
430 index[to] = index[from];
431 pieceList[c][pt][index[to]] = to;
434 #endif // #ifndef POSITION_H_INCLUDED