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, bool givesCheck);
142 void undo_move(Move m);
143 void do_null_move(StateInfo& st);
144 void undo_null_move();
146 // Static exchange evaluation
147 Value see(Move m) const;
148 Value see_sign(Move m) const;
150 // Accessing hash keys
152 Key key_after(Move m) const;
153 Key exclusion_key() const;
154 Key material_key() const;
155 Key pawn_key() const;
157 // Other properties of the position
158 Color side_to_move() const;
159 Phase game_phase() const;
160 int game_ply() const;
161 bool is_chess960() const;
162 Thread* this_thread() const;
163 uint64_t nodes_searched() const;
164 void set_nodes_searched(uint64_t n);
165 bool is_draw() const;
166 int rule50_count() const;
167 Score psq_score() const;
168 Value non_pawn_material(Color c) const;
170 // Position consistency check, for debugging
171 bool pos_is_ok(int* failedStep = nullptr) const;
175 // Initialization helpers (used while setting up a position)
177 void set_castling_right(Color c, Square rfrom);
178 void set_state(StateInfo* si) const;
181 Bitboard check_blockers(Color c, Color kingColor) const;
182 void put_piece(Color c, PieceType pt, Square s);
183 void remove_piece(Color c, PieceType pt, Square s);
184 void move_piece(Color c, PieceType pt, Square from, Square to);
186 void do_castling(Color us, Square from, Square& to, Square& rfrom, Square& rto);
189 Piece board[SQUARE_NB];
190 Bitboard byTypeBB[PIECE_TYPE_NB];
191 Bitboard byColorBB[COLOR_NB];
192 int pieceCount[COLOR_NB][PIECE_TYPE_NB];
193 Square pieceList[COLOR_NB][PIECE_TYPE_NB][16];
194 int index[SQUARE_NB];
195 int castlingRightsMask[SQUARE_NB];
196 Square castlingRookSquare[CASTLING_RIGHT_NB];
197 Bitboard castlingPath[CASTLING_RIGHT_NB];
198 StateInfo startState;
207 inline Color Position::side_to_move() const {
211 inline bool Position::empty(Square s) const {
212 return board[s] == NO_PIECE;
215 inline Piece Position::piece_on(Square s) const {
219 inline Piece Position::moved_piece(Move m) const {
220 return board[from_sq(m)];
223 inline Bitboard Position::pieces() const {
224 return byTypeBB[ALL_PIECES];
227 inline Bitboard Position::pieces(PieceType pt) const {
231 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2) const {
232 return byTypeBB[pt1] | byTypeBB[pt2];
235 inline Bitboard Position::pieces(Color c) const {
239 inline Bitboard Position::pieces(Color c, PieceType pt) const {
240 return byColorBB[c] & byTypeBB[pt];
243 inline Bitboard Position::pieces(Color c, PieceType pt1, PieceType pt2) const {
244 return byColorBB[c] & (byTypeBB[pt1] | byTypeBB[pt2]);
247 template<PieceType Pt> inline int Position::count(Color c) const {
248 return pieceCount[c][Pt];
251 template<PieceType Pt> inline const Square* Position::list(Color c) const {
252 return pieceList[c][Pt];
255 inline Square Position::king_square(Color c) const {
256 return pieceList[c][KING][0];
259 inline Square Position::ep_square() const {
263 inline int Position::can_castle(CastlingRight cr) const {
264 return st->castlingRights & cr;
267 inline int Position::can_castle(Color c) const {
268 return st->castlingRights & ((WHITE_OO | WHITE_OOO) << (2 * c));
271 inline bool Position::castling_impeded(CastlingRight cr) const {
272 return byTypeBB[ALL_PIECES] & castlingPath[cr];
275 inline Square Position::castling_rook_square(CastlingRight cr) const {
276 return castlingRookSquare[cr];
279 template<PieceType Pt>
280 inline Bitboard Position::attacks_from(Square s) const {
281 return Pt == BISHOP || Pt == ROOK ? attacks_bb<Pt>(s, byTypeBB[ALL_PIECES])
282 : Pt == QUEEN ? attacks_from<ROOK>(s) | attacks_from<BISHOP>(s)
283 : StepAttacksBB[Pt][s];
287 inline Bitboard Position::attacks_from<PAWN>(Square s, Color c) const {
288 return StepAttacksBB[make_piece(c, PAWN)][s];
291 inline Bitboard Position::attacks_from(Piece pc, Square s) const {
292 return attacks_bb(pc, s, byTypeBB[ALL_PIECES]);
295 inline Bitboard Position::attackers_to(Square s) const {
296 return attackers_to(s, byTypeBB[ALL_PIECES]);
299 inline Bitboard Position::checkers() const {
300 return st->checkersBB;
303 inline Bitboard Position::discovered_check_candidates() const {
304 return check_blockers(sideToMove, ~sideToMove);
307 inline Bitboard Position::pinned_pieces(Color c) const {
308 return check_blockers(c, c);
311 inline bool Position::pawn_passed(Color c, Square s) const {
312 return !(pieces(~c, PAWN) & passed_pawn_mask(c, s));
315 inline bool Position::advanced_pawn_push(Move m) const {
316 return type_of(moved_piece(m)) == PAWN
317 && relative_rank(sideToMove, from_sq(m)) > RANK_4;
320 inline Key Position::key() const {
324 inline Key Position::pawn_key() const {
328 inline Key Position::material_key() const {
329 return st->materialKey;
332 inline Score Position::psq_score() const {
336 inline Value Position::non_pawn_material(Color c) const {
337 return st->nonPawnMaterial[c];
340 inline int Position::game_ply() const {
344 inline int Position::rule50_count() const {
348 inline uint64_t Position::nodes_searched() const {
352 inline void Position::set_nodes_searched(uint64_t n) {
356 inline bool Position::opposite_bishops() const {
357 return pieceCount[WHITE][BISHOP] == 1
358 && pieceCount[BLACK][BISHOP] == 1
359 && opposite_colors(pieceList[WHITE][BISHOP][0], pieceList[BLACK][BISHOP][0]);
362 inline bool Position::pawn_on_7th(Color c) const {
363 return pieces(c, PAWN) & rank_bb(relative_rank(c, RANK_7));
366 inline bool Position::is_chess960() const {
370 inline bool Position::capture_or_promotion(Move m) const {
373 return type_of(m) != NORMAL ? type_of(m) != CASTLING : !empty(to_sq(m));
376 inline bool Position::capture(Move m) const {
378 // Castling is encoded as "king captures the rook"
380 return (!empty(to_sq(m)) && type_of(m) != CASTLING) || type_of(m) == ENPASSANT;
383 inline PieceType Position::captured_piece_type() const {
384 return st->capturedType;
387 inline Thread* Position::this_thread() const {
391 inline void Position::put_piece(Color c, PieceType pt, Square s) {
393 board[s] = make_piece(c, pt);
394 byTypeBB[ALL_PIECES] |= s;
397 index[s] = pieceCount[c][pt]++;
398 pieceList[c][pt][index[s]] = s;
399 pieceCount[c][ALL_PIECES]++;
402 inline void Position::remove_piece(Color c, PieceType pt, Square s) {
404 // WARNING: This is not a reversible operation. If we remove a piece in
405 // do_move() and then replace it in undo_move() we will put it at the end of
406 // the list and not in its original place, it means index[] and pieceList[]
407 // are not guaranteed to be invariant to a do_move() + undo_move() sequence.
408 byTypeBB[ALL_PIECES] ^= s;
411 /* board[s] = NO_PIECE; Not needed, overwritten by the capturing one */
412 Square lastSquare = pieceList[c][pt][--pieceCount[c][pt]];
413 index[lastSquare] = index[s];
414 pieceList[c][pt][index[lastSquare]] = lastSquare;
415 pieceList[c][pt][pieceCount[c][pt]] = SQ_NONE;
416 pieceCount[c][ALL_PIECES]--;
419 inline void Position::move_piece(Color c, PieceType pt, Square from, Square to) {
421 // index[from] is not updated and becomes stale. This works as long as index[]
422 // is accessed just by known occupied squares.
423 Bitboard from_to_bb = SquareBB[from] ^ SquareBB[to];
424 byTypeBB[ALL_PIECES] ^= from_to_bb;
425 byTypeBB[pt] ^= from_to_bb;
426 byColorBB[c] ^= from_to_bb;
427 board[from] = NO_PIECE;
428 board[to] = make_piece(c, pt);
429 index[to] = index[from];
430 pieceList[c][pt][index[to]] = to;
433 #endif // #ifndef POSITION_H_INCLUDED