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) 2015-2016 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];
49 // Not copied when making a move (will be recomputed anyhow)
54 Bitboard blockersForKing[COLOR_NB];
55 Bitboard pinnersForKing[COLOR_NB];
56 Bitboard checkSquares[PIECE_TYPE_NB];
59 // In a std::deque references to elements are unaffected upon resizing
60 typedef std::unique_ptr<std::deque<StateInfo>> StateListPtr;
63 /// Position class stores information regarding the board representation as
64 /// pieces, side to move, hash keys, castling info, etc. Important methods are
65 /// do_move() and undo_move(), used by the search to update node info when
66 /// traversing the search tree.
74 Position(const Position&) = delete;
75 Position& operator=(const Position&) = delete;
77 // FEN string input/output
78 Position& set(const std::string& fenStr, bool isChess960, StateInfo* si, Thread* th);
79 const std::string fen() const;
81 // Position representation
82 Bitboard pieces() const;
83 Bitboard pieces(PieceType pt) const;
84 Bitboard pieces(PieceType pt1, PieceType pt2) const;
85 Bitboard pieces(Color c) const;
86 Bitboard pieces(Color c, PieceType pt) const;
87 Bitboard pieces(Color c, PieceType pt1, PieceType pt2) const;
88 Piece piece_on(Square s) const;
89 Square ep_square() const;
90 bool empty(Square s) const;
91 template<PieceType Pt> int count(Color c) const;
92 template<PieceType Pt> const Square* squares(Color c) const;
93 template<PieceType Pt> Square square(Color c) const;
96 int can_castle(Color c) const;
97 int can_castle(CastlingRight cr) const;
98 bool castling_impeded(CastlingRight cr) const;
99 Square castling_rook_square(CastlingRight cr) const;
102 Bitboard checkers() const;
103 Bitboard discovered_check_candidates() const;
104 Bitboard pinned_pieces(Color c) const;
105 Bitboard check_squares(PieceType pt) const;
107 // Attacks to/from a given square
108 Bitboard attackers_to(Square s) const;
109 Bitboard attackers_to(Square s, Bitboard occupied) const;
110 Bitboard attacks_from(Piece pc, Square s) const;
111 template<PieceType> Bitboard attacks_from(Square s) const;
112 template<PieceType> Bitboard attacks_from(Square s, Color c) const;
113 Bitboard slider_blockers(Bitboard sliders, Square s, Bitboard& pinners) const;
115 // Properties of moves
116 bool legal(Move m) const;
117 bool pseudo_legal(const Move m) const;
118 bool capture(Move m) const;
119 bool capture_or_promotion(Move m) const;
120 bool gives_check(Move m) const;
121 bool advanced_pawn_push(Move m) const;
122 Piece moved_piece(Move m) const;
123 Piece captured_piece() const;
126 bool pawn_passed(Color c, Square s) const;
127 bool opposite_bishops() const;
129 // Doing and undoing moves
130 void do_move(Move m, StateInfo& st, bool givesCheck);
131 void undo_move(Move m);
132 void do_null_move(StateInfo& st);
133 void undo_null_move();
135 // Static Exchange Evaluation
136 bool see_ge(Move m, Value value) const;
138 // Accessing hash keys
140 Key key_after(Move m) const;
141 Key material_key() const;
142 Key pawn_key() const;
144 // Other properties of the position
145 Color side_to_move() const;
146 Phase game_phase() const;
147 int game_ply() const;
148 bool is_chess960() const;
149 Thread* this_thread() const;
150 uint64_t nodes_searched() const;
151 bool is_draw() const;
152 int rule50_count() const;
153 Score psq_score() const;
154 Value non_pawn_material(Color c) const;
156 // Position consistency check, for debugging
157 bool pos_is_ok(int* failedStep = nullptr) const;
161 // Initialization helpers (used while setting up a position)
162 void set_castling_right(Color c, Square rfrom);
163 void set_state(StateInfo* si) const;
164 void set_check_info(StateInfo* si) const;
167 void put_piece(Piece pc, Square s);
168 void remove_piece(Piece pc, Square s);
169 void move_piece(Piece pc, Square from, Square to);
171 void do_castling(Color us, Square from, Square& to, Square& rfrom, Square& rto);
174 Piece board[SQUARE_NB];
175 Bitboard byTypeBB[PIECE_TYPE_NB];
176 Bitboard byColorBB[COLOR_NB];
177 int pieceCount[PIECE_NB];
178 Square pieceList[PIECE_NB][16];
179 int index[SQUARE_NB];
180 int castlingRightsMask[SQUARE_NB];
181 Square castlingRookSquare[CASTLING_RIGHT_NB];
182 Bitboard castlingPath[CASTLING_RIGHT_NB];
191 extern std::ostream& operator<<(std::ostream& os, const Position& pos);
193 inline Color Position::side_to_move() const {
197 inline bool Position::empty(Square s) const {
198 return board[s] == NO_PIECE;
201 inline Piece Position::piece_on(Square s) const {
205 inline Piece Position::moved_piece(Move m) const {
206 return board[from_sq(m)];
209 inline Bitboard Position::pieces() const {
210 return byTypeBB[ALL_PIECES];
213 inline Bitboard Position::pieces(PieceType pt) const {
217 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2) const {
218 return byTypeBB[pt1] | byTypeBB[pt2];
221 inline Bitboard Position::pieces(Color c) const {
225 inline Bitboard Position::pieces(Color c, PieceType pt) const {
226 return byColorBB[c] & byTypeBB[pt];
229 inline Bitboard Position::pieces(Color c, PieceType pt1, PieceType pt2) const {
230 return byColorBB[c] & (byTypeBB[pt1] | byTypeBB[pt2]);
233 template<PieceType Pt> inline int Position::count(Color c) const {
234 return pieceCount[make_piece(c, Pt)];
237 template<PieceType Pt> inline const Square* Position::squares(Color c) const {
238 return pieceList[make_piece(c, Pt)];
241 template<PieceType Pt> inline Square Position::square(Color c) const {
242 assert(pieceCount[make_piece(c, Pt)] == 1);
243 return pieceList[make_piece(c, Pt)][0];
246 inline Square Position::ep_square() const {
250 inline int Position::can_castle(CastlingRight cr) const {
251 return st->castlingRights & cr;
254 inline int Position::can_castle(Color c) const {
255 return st->castlingRights & ((WHITE_OO | WHITE_OOO) << (2 * c));
258 inline bool Position::castling_impeded(CastlingRight cr) const {
259 return byTypeBB[ALL_PIECES] & castlingPath[cr];
262 inline Square Position::castling_rook_square(CastlingRight cr) const {
263 return castlingRookSquare[cr];
266 template<PieceType Pt>
267 inline Bitboard Position::attacks_from(Square s) const {
268 return Pt == BISHOP || Pt == ROOK ? attacks_bb<Pt>(s, byTypeBB[ALL_PIECES])
269 : Pt == QUEEN ? attacks_from<ROOK>(s) | attacks_from<BISHOP>(s)
270 : StepAttacksBB[Pt][s];
274 inline Bitboard Position::attacks_from<PAWN>(Square s, Color c) const {
275 return StepAttacksBB[make_piece(c, PAWN)][s];
278 inline Bitboard Position::attacks_from(Piece pc, Square s) const {
279 return attacks_bb(pc, s, byTypeBB[ALL_PIECES]);
282 inline Bitboard Position::attackers_to(Square s) const {
283 return attackers_to(s, byTypeBB[ALL_PIECES]);
286 inline Bitboard Position::checkers() const {
287 return st->checkersBB;
290 inline Bitboard Position::discovered_check_candidates() const {
291 return st->blockersForKing[~sideToMove] & pieces(sideToMove);
294 inline Bitboard Position::pinned_pieces(Color c) const {
295 return st->blockersForKing[c] & pieces(c);
298 inline Bitboard Position::check_squares(PieceType pt) const {
299 return st->checkSquares[pt];
302 inline bool Position::pawn_passed(Color c, Square s) const {
303 return !(pieces(~c, PAWN) & passed_pawn_mask(c, s));
306 inline bool Position::advanced_pawn_push(Move m) const {
307 return type_of(moved_piece(m)) == PAWN
308 && relative_rank(sideToMove, from_sq(m)) > RANK_4;
311 inline Key Position::key() const {
315 inline Key Position::pawn_key() const {
319 inline Key Position::material_key() const {
320 return st->materialKey;
323 inline Score Position::psq_score() const {
327 inline Value Position::non_pawn_material(Color c) const {
328 return st->nonPawnMaterial[c];
331 inline int Position::game_ply() const {
335 inline int Position::rule50_count() const {
339 inline uint64_t Position::nodes_searched() const {
343 inline bool Position::opposite_bishops() const {
344 return pieceCount[W_BISHOP] == 1
345 && pieceCount[B_BISHOP] == 1
346 && opposite_colors(square<BISHOP>(WHITE), square<BISHOP>(BLACK));
349 inline bool Position::is_chess960() const {
353 inline bool Position::capture_or_promotion(Move m) const {
355 return type_of(m) != NORMAL ? type_of(m) != CASTLING : !empty(to_sq(m));
358 inline bool Position::capture(Move m) const {
360 // Castling is encoded as "king captures rook"
361 return (!empty(to_sq(m)) && type_of(m) != CASTLING) || type_of(m) == ENPASSANT;
364 inline Piece Position::captured_piece() const {
365 return st->capturedPiece;
368 inline Thread* Position::this_thread() const {
372 inline void Position::put_piece(Piece pc, Square s) {
375 byTypeBB[ALL_PIECES] |= s;
376 byTypeBB[type_of(pc)] |= s;
377 byColorBB[color_of(pc)] |= s;
378 index[s] = pieceCount[pc]++;
379 pieceList[pc][index[s]] = s;
380 pieceCount[make_piece(color_of(pc), ALL_PIECES)]++;
383 inline void Position::remove_piece(Piece pc, Square s) {
385 // WARNING: This is not a reversible operation. If we remove a piece in
386 // do_move() and then replace it in undo_move() we will put it at the end of
387 // the list and not in its original place, it means index[] and pieceList[]
388 // are not invariant to a do_move() + undo_move() sequence.
389 byTypeBB[ALL_PIECES] ^= s;
390 byTypeBB[type_of(pc)] ^= s;
391 byColorBB[color_of(pc)] ^= s;
392 /* board[s] = NO_PIECE; Not needed, overwritten by the capturing one */
393 Square lastSquare = pieceList[pc][--pieceCount[pc]];
394 index[lastSquare] = index[s];
395 pieceList[pc][index[lastSquare]] = lastSquare;
396 pieceList[pc][pieceCount[pc]] = SQ_NONE;
397 pieceCount[make_piece(color_of(pc), ALL_PIECES)]--;
400 inline void Position::move_piece(Piece pc, Square from, Square to) {
402 // index[from] is not updated and becomes stale. This works as long as index[]
403 // is accessed just by known occupied squares.
404 Bitboard from_to_bb = SquareBB[from] ^ SquareBB[to];
405 byTypeBB[ALL_PIECES] ^= from_to_bb;
406 byTypeBB[type_of(pc)] ^= from_to_bb;
407 byColorBB[color_of(pc)] ^= from_to_bb;
408 board[from] = NO_PIECE;
410 index[to] = index[from];
411 pieceList[pc][index[to]] = to;
414 #endif // #ifndef POSITION_H_INCLUDED