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()
35 extern Score psq[COLOR_NB][PIECE_TYPE_NB][SQUARE_NB];
40 /// CheckInfo struct is initialized at c'tor time and keeps info used to detect
41 /// if a move gives check.
45 explicit CheckInfo(const Position&);
47 Bitboard dcCandidates;
49 Bitboard checkSquares[PIECE_TYPE_NB];
54 /// StateInfo struct stores information needed to restore a Position object to
55 /// its previous state when we retract a move. Whenever a move is made on the
56 /// board (by calling Position::do_move), a StateInfo object must be passed.
60 // Copied when making a move
63 Value nonPawnMaterial[COLOR_NB];
70 // Not copied when making a move
73 PieceType capturedType;
78 /// Position class stores information regarding the board representation as
79 /// pieces, side to move, hash keys, castling info, etc. Important methods are
80 /// do_move() and undo_move(), used by the search to update node info when
81 /// traversing the search tree.
85 friend std::ostream& operator<<(std::ostream&, const Position&);
90 Position() = default; // To define the global object RootPos
91 Position(const Position&) = delete;
92 Position(const Position& pos, Thread* th) { *this = pos; thisThread = th; }
93 Position(const std::string& f, bool c960, Thread* th) { set(f, c960, th); }
94 Position& operator=(const Position&); // To assign RootPos from UCI
96 // FEN string input/output
97 void set(const std::string& fenStr, bool isChess960, Thread* th);
98 const std::string fen() const;
100 // Position representation
101 Bitboard pieces() const;
102 Bitboard pieces(PieceType pt) const;
103 Bitboard pieces(PieceType pt1, PieceType pt2) const;
104 Bitboard pieces(Color c) const;
105 Bitboard pieces(Color c, PieceType pt) const;
106 Bitboard pieces(Color c, PieceType pt1, PieceType pt2) const;
107 Piece piece_on(Square s) const;
108 Square king_square(Color c) const;
109 Square ep_square() const;
110 bool empty(Square s) const;
111 template<PieceType Pt> int count(Color c) const;
112 template<PieceType Pt> const Square* list(Color c) const;
115 int can_castle(Color c) const;
116 int can_castle(CastlingRight cr) const;
117 bool castling_impeded(CastlingRight cr) const;
118 Square castling_rook_square(CastlingRight cr) const;
121 Bitboard checkers() const;
122 Bitboard discovered_check_candidates() const;
123 Bitboard pinned_pieces(Color c) const;
125 // Attacks to/from a given square
126 Bitboard attackers_to(Square s) const;
127 Bitboard attackers_to(Square s, Bitboard occupied) const;
128 Bitboard attacks_from(Piece pc, Square s) const;
129 template<PieceType> Bitboard attacks_from(Square s) const;
130 template<PieceType> Bitboard attacks_from(Square s, Color c) const;
132 // Properties of moves
133 bool legal(Move m, Bitboard pinned) const;
134 bool pseudo_legal(const Move m) const;
135 bool capture(Move m) const;
136 bool capture_or_promotion(Move m) const;
137 bool gives_check(Move m, const CheckInfo& ci) const;
138 bool advanced_pawn_push(Move m) const;
139 Piece moved_piece(Move m) const;
140 PieceType captured_piece_type() const;
143 bool pawn_passed(Color c, Square s) const;
144 bool opposite_bishops() const;
146 // Doing and undoing moves
147 void do_move(Move m, StateInfo& st, bool givesCheck);
148 void undo_move(Move m);
149 void do_null_move(StateInfo& st);
150 void undo_null_move();
152 // Static exchange evaluation
153 Value see(Move m) const;
154 Value see_sign(Move m) const;
156 // Accessing hash keys
158 Key key_after(Move m) const;
159 Key exclusion_key() const;
160 Key material_key() const;
161 Key pawn_key() const;
163 // Other properties of the position
164 Color side_to_move() const;
165 Phase game_phase() const;
166 int game_ply() const;
167 bool is_chess960() const;
168 Thread* this_thread() const;
169 uint64_t nodes_searched() const;
170 void set_nodes_searched(uint64_t n);
171 bool is_draw() const;
172 int rule50_count() const;
173 Score psq_score() const;
174 Value non_pawn_material(Color c) const;
176 // Position consistency check, for debugging
177 bool pos_is_ok(int* failedStep = nullptr) const;
181 // Initialization helpers (used while setting up a position)
183 void set_castling_right(Color c, Square rfrom);
184 void set_state(StateInfo* si) const;
187 Bitboard check_blockers(Color c, Color kingColor) const;
188 void put_piece(Color c, PieceType pt, Square s);
189 void remove_piece(Color c, PieceType pt, Square s);
190 void move_piece(Color c, PieceType pt, Square from, Square to);
192 void do_castling(Color us, Square from, Square& to, Square& rfrom, Square& rto);
195 Piece board[SQUARE_NB];
196 Bitboard byTypeBB[PIECE_TYPE_NB];
197 Bitboard byColorBB[COLOR_NB];
198 int pieceCount[COLOR_NB][PIECE_TYPE_NB];
199 Square pieceList[COLOR_NB][PIECE_TYPE_NB][16];
200 int index[SQUARE_NB];
201 int castlingRightsMask[SQUARE_NB];
202 Square castlingRookSquare[CASTLING_RIGHT_NB];
203 Bitboard castlingPath[CASTLING_RIGHT_NB];
204 StateInfo startState;
213 inline Color Position::side_to_move() const {
217 inline bool Position::empty(Square s) const {
218 return board[s] == NO_PIECE;
221 inline Piece Position::piece_on(Square s) const {
225 inline Piece Position::moved_piece(Move m) const {
226 return board[from_sq(m)];
229 inline Bitboard Position::pieces() const {
230 return byTypeBB[ALL_PIECES];
233 inline Bitboard Position::pieces(PieceType pt) const {
237 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2) const {
238 return byTypeBB[pt1] | byTypeBB[pt2];
241 inline Bitboard Position::pieces(Color c) const {
245 inline Bitboard Position::pieces(Color c, PieceType pt) const {
246 return byColorBB[c] & byTypeBB[pt];
249 inline Bitboard Position::pieces(Color c, PieceType pt1, PieceType pt2) const {
250 return byColorBB[c] & (byTypeBB[pt1] | byTypeBB[pt2]);
253 template<PieceType Pt> inline int Position::count(Color c) const {
254 return pieceCount[c][Pt];
257 template<PieceType Pt> inline const Square* Position::list(Color c) const {
258 return pieceList[c][Pt];
261 inline Square Position::king_square(Color c) const {
262 return pieceList[c][KING][0];
265 inline Square Position::ep_square() const {
269 inline int Position::can_castle(CastlingRight cr) const {
270 return st->castlingRights & cr;
273 inline int Position::can_castle(Color c) const {
274 return st->castlingRights & ((WHITE_OO | WHITE_OOO) << (2 * c));
277 inline bool Position::castling_impeded(CastlingRight cr) const {
278 return byTypeBB[ALL_PIECES] & castlingPath[cr];
281 inline Square Position::castling_rook_square(CastlingRight cr) const {
282 return castlingRookSquare[cr];
285 template<PieceType Pt>
286 inline Bitboard Position::attacks_from(Square s) const {
287 return Pt == BISHOP || Pt == ROOK ? attacks_bb<Pt>(s, byTypeBB[ALL_PIECES])
288 : Pt == QUEEN ? attacks_from<ROOK>(s) | attacks_from<BISHOP>(s)
289 : StepAttacksBB[Pt][s];
293 inline Bitboard Position::attacks_from<PAWN>(Square s, Color c) const {
294 return StepAttacksBB[make_piece(c, PAWN)][s];
297 inline Bitboard Position::attacks_from(Piece pc, Square s) const {
298 return attacks_bb(pc, s, byTypeBB[ALL_PIECES]);
301 inline Bitboard Position::attackers_to(Square s) const {
302 return attackers_to(s, byTypeBB[ALL_PIECES]);
305 inline Bitboard Position::checkers() const {
306 return st->checkersBB;
309 inline Bitboard Position::discovered_check_candidates() const {
310 return check_blockers(sideToMove, ~sideToMove);
313 inline Bitboard Position::pinned_pieces(Color c) const {
314 return check_blockers(c, c);
317 inline bool Position::pawn_passed(Color c, Square s) const {
318 return !(pieces(~c, PAWN) & passed_pawn_mask(c, s));
321 inline bool Position::advanced_pawn_push(Move m) const {
322 return type_of(moved_piece(m)) == PAWN
323 && relative_rank(sideToMove, from_sq(m)) > RANK_4;
326 inline Key Position::key() const {
330 inline Key Position::pawn_key() const {
334 inline Key Position::material_key() const {
335 return st->materialKey;
338 inline Score Position::psq_score() const {
342 inline Value Position::non_pawn_material(Color c) const {
343 return st->nonPawnMaterial[c];
346 inline int Position::game_ply() const {
350 inline int Position::rule50_count() const {
354 inline uint64_t Position::nodes_searched() const {
358 inline void Position::set_nodes_searched(uint64_t n) {
362 inline bool Position::opposite_bishops() const {
363 return pieceCount[WHITE][BISHOP] == 1
364 && pieceCount[BLACK][BISHOP] == 1
365 && opposite_colors(pieceList[WHITE][BISHOP][0], pieceList[BLACK][BISHOP][0]);
368 inline bool Position::is_chess960() const {
372 inline bool Position::capture_or_promotion(Move m) const {
375 return type_of(m) != NORMAL ? type_of(m) != CASTLING : !empty(to_sq(m));
378 inline bool Position::capture(Move m) const {
380 // Castling is encoded as "king captures the rook"
382 return (!empty(to_sq(m)) && type_of(m) != CASTLING) || type_of(m) == ENPASSANT;
385 inline PieceType Position::captured_piece_type() const {
386 return st->capturedType;
389 inline Thread* Position::this_thread() const {
393 inline void Position::put_piece(Color c, PieceType pt, Square s) {
395 board[s] = make_piece(c, pt);
396 byTypeBB[ALL_PIECES] |= s;
399 index[s] = pieceCount[c][pt]++;
400 pieceList[c][pt][index[s]] = s;
401 pieceCount[c][ALL_PIECES]++;
404 inline void Position::remove_piece(Color c, PieceType pt, Square s) {
406 // WARNING: This is not a reversible operation. If we remove a piece in
407 // do_move() and then replace it in undo_move() we will put it at the end of
408 // the list and not in its original place, it means index[] and pieceList[]
409 // are not guaranteed to be invariant to a do_move() + undo_move() sequence.
410 byTypeBB[ALL_PIECES] ^= s;
413 /* board[s] = NO_PIECE; Not needed, overwritten by the capturing one */
414 Square lastSquare = pieceList[c][pt][--pieceCount[c][pt]];
415 index[lastSquare] = index[s];
416 pieceList[c][pt][index[lastSquare]] = lastSquare;
417 pieceList[c][pt][pieceCount[c][pt]] = SQ_NONE;
418 pieceCount[c][ALL_PIECES]--;
421 inline void Position::move_piece(Color c, PieceType pt, Square from, Square to) {
423 // index[from] is not updated and becomes stale. This works as long as index[]
424 // is accessed just by known occupied squares.
425 Bitboard from_to_bb = SquareBB[from] ^ SquareBB[to];
426 byTypeBB[ALL_PIECES] ^= from_to_bb;
427 byTypeBB[pt] ^= from_to_bb;
428 byColorBB[c] ^= from_to_bb;
429 board[from] = NO_PIECE;
430 board[to] = make_piece(c, pt);
431 index[to] = index[from];
432 pieceList[c][pt][index[to]] = to;
435 #endif // #ifndef POSITION_H_INCLUDED