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) 2015-2018 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 pinners[COLOR_NB];
56 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() const;
87 Bitboard pieces(PieceType pt) const;
88 Bitboard pieces(PieceType pt1, PieceType pt2) const;
89 Bitboard pieces(Color c) const;
90 Bitboard pieces(Color c, PieceType pt) const;
91 Bitboard pieces(Color c, PieceType pt1, PieceType pt2) const;
92 Piece piece_on(Square s) const;
93 Square ep_square() const;
94 bool empty(Square s) const;
95 template<PieceType Pt> int count(Color c) const;
96 template<PieceType Pt> int count() const;
97 template<PieceType Pt> const Square* squares(Color c) const;
98 template<PieceType Pt> Square square(Color c) const;
101 int can_castle(Color c) const;
102 int can_castle(CastlingRight cr) const;
103 bool castling_impeded(CastlingRight cr) const;
104 Square castling_rook_square(CastlingRight cr) const;
107 Bitboard checkers() const;
108 Bitboard blockers_for_king(Color c) const;
109 Bitboard check_squares(PieceType pt) const;
111 // Attacks to/from a given square
112 Bitboard attackers_to(Square s) const;
113 Bitboard attackers_to(Square s, Bitboard occupied) const;
114 Bitboard attacks_from(PieceType pt, Square s) const;
115 template<PieceType> Bitboard attacks_from(Square s) const;
116 template<PieceType> Bitboard attacks_from(Square s, Color c) const;
117 Bitboard slider_blockers(Bitboard sliders, Square s, Bitboard& pinners) const;
119 // Properties of moves
120 bool legal(Move m) const;
121 bool pseudo_legal(const Move m) const;
122 bool capture(Move m) const;
123 bool capture_or_promotion(Move m) const;
124 bool gives_check(Move m) const;
125 bool advanced_pawn_push(Move m) const;
126 Piece moved_piece(Move m) const;
127 Piece captured_piece() const;
130 bool pawn_passed(Color c, Square s) const;
131 bool opposite_bishops() const;
133 // Doing and undoing moves
134 void do_move(Move m, StateInfo& newSt);
135 void do_move(Move m, StateInfo& newSt, bool givesCheck);
136 void undo_move(Move m);
137 void do_null_move(StateInfo& newSt);
138 void undo_null_move();
140 // Static Exchange Evaluation
141 bool see_ge(Move m, Value threshold = VALUE_ZERO) const;
143 // Accessing hash keys
145 Key key_after(Move m) const;
146 Key material_key() const;
147 Key pawn_key() const;
149 // Other properties of the position
150 Color side_to_move() const;
151 int game_ply() const;
152 bool is_chess960() const;
153 Thread* this_thread() const;
154 bool is_draw(int ply) const;
155 bool has_game_cycle(int ply) const;
156 bool has_repeated() const;
157 int rule50_count() const;
158 Score psq_score() const;
159 Value non_pawn_material(Color c) const;
160 Value non_pawn_material() const;
162 // Position consistency check, for debugging
163 bool pos_is_ok() const;
167 // Initialization helpers (used while setting up a position)
168 void set_castling_right(Color c, Square rfrom);
169 void set_state(StateInfo* si) const;
170 void set_check_info(StateInfo* si) const;
173 void put_piece(Piece pc, Square s);
174 void remove_piece(Piece pc, Square s);
175 void move_piece(Piece pc, Square from, Square to);
177 void do_castling(Color us, Square from, Square& to, Square& rfrom, Square& rto);
180 Piece board[SQUARE_NB];
181 Bitboard byTypeBB[PIECE_TYPE_NB];
182 Bitboard byColorBB[COLOR_NB];
183 int pieceCount[PIECE_NB];
184 Square pieceList[PIECE_NB][16];
185 int index[SQUARE_NB];
186 int castlingRightsMask[SQUARE_NB];
187 Square castlingRookSquare[CASTLING_RIGHT_NB];
188 Bitboard castlingPath[CASTLING_RIGHT_NB];
196 extern std::ostream& operator<<(std::ostream& os, const Position& pos);
198 inline Color Position::side_to_move() const {
202 inline bool Position::empty(Square s) const {
203 return board[s] == NO_PIECE;
206 inline Piece Position::piece_on(Square s) const {
210 inline Piece Position::moved_piece(Move m) const {
211 return board[from_sq(m)];
214 inline Bitboard Position::pieces() const {
215 return byTypeBB[ALL_PIECES];
218 inline Bitboard Position::pieces(PieceType pt) const {
222 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2) const {
223 return byTypeBB[pt1] | byTypeBB[pt2];
226 inline Bitboard Position::pieces(Color c) const {
230 inline Bitboard Position::pieces(Color c, PieceType pt) const {
231 return byColorBB[c] & byTypeBB[pt];
234 inline Bitboard Position::pieces(Color c, PieceType pt1, PieceType pt2) const {
235 return byColorBB[c] & (byTypeBB[pt1] | byTypeBB[pt2]);
238 template<PieceType Pt> inline int Position::count(Color c) const {
239 return pieceCount[make_piece(c, Pt)];
242 template<PieceType Pt> inline int Position::count() const {
243 return pieceCount[make_piece(WHITE, Pt)] + pieceCount[make_piece(BLACK, Pt)];
246 template<PieceType Pt> inline const Square* Position::squares(Color c) const {
247 return pieceList[make_piece(c, Pt)];
250 template<PieceType Pt> inline Square Position::square(Color c) const {
251 assert(pieceCount[make_piece(c, Pt)] == 1);
252 return pieceList[make_piece(c, Pt)][0];
255 inline Square Position::ep_square() const {
259 inline int Position::can_castle(CastlingRight cr) const {
260 return st->castlingRights & cr;
263 inline int Position::can_castle(Color c) const {
264 return st->castlingRights & ((WHITE_OO | WHITE_OOO) << (2 * c));
267 inline bool Position::castling_impeded(CastlingRight cr) const {
268 return byTypeBB[ALL_PIECES] & castlingPath[cr];
271 inline Square Position::castling_rook_square(CastlingRight cr) const {
272 return castlingRookSquare[cr];
275 template<PieceType Pt>
276 inline Bitboard Position::attacks_from(Square s) const {
278 return Pt == BISHOP || Pt == ROOK ? attacks_bb<Pt>(s, byTypeBB[ALL_PIECES])
279 : Pt == QUEEN ? attacks_from<ROOK>(s) | attacks_from<BISHOP>(s)
280 : PseudoAttacks[Pt][s];
284 inline Bitboard Position::attacks_from<PAWN>(Square s, Color c) const {
285 return PawnAttacks[c][s];
288 inline Bitboard Position::attacks_from(PieceType pt, Square s) const {
289 return attacks_bb(pt, s, byTypeBB[ALL_PIECES]);
292 inline Bitboard Position::attackers_to(Square s) const {
293 return attackers_to(s, byTypeBB[ALL_PIECES]);
296 inline Bitboard Position::checkers() const {
297 return st->checkersBB;
300 inline Bitboard Position::blockers_for_king(Color c) const {
301 return st->blockersForKing[c];
304 inline Bitboard Position::check_squares(PieceType pt) const {
305 return st->checkSquares[pt];
308 inline bool Position::pawn_passed(Color c, Square s) const {
309 return !(pieces(~c, PAWN) & passed_pawn_mask(c, s));
312 inline bool Position::advanced_pawn_push(Move m) const {
313 return type_of(moved_piece(m)) == PAWN
314 && relative_rank(sideToMove, from_sq(m)) > RANK_4;
317 inline Key Position::key() const {
321 inline Key Position::pawn_key() const {
325 inline Key Position::material_key() const {
326 return st->materialKey;
329 inline Score Position::psq_score() const {
333 inline Value Position::non_pawn_material(Color c) const {
334 return st->nonPawnMaterial[c];
337 inline Value Position::non_pawn_material() const {
338 return st->nonPawnMaterial[WHITE] + st->nonPawnMaterial[BLACK];
341 inline int Position::game_ply() const {
345 inline int Position::rule50_count() const {
349 inline bool Position::opposite_bishops() const {
350 return pieceCount[W_BISHOP] == 1
351 && pieceCount[B_BISHOP] == 1
352 && opposite_colors(square<BISHOP>(WHITE), square<BISHOP>(BLACK));
355 inline bool Position::is_chess960() const {
359 inline bool Position::capture_or_promotion(Move m) const {
361 return type_of(m) != NORMAL ? type_of(m) != CASTLING : !empty(to_sq(m));
364 inline bool Position::capture(Move m) const {
366 // Castling is encoded as "king captures rook"
367 return (!empty(to_sq(m)) && type_of(m) != CASTLING) || type_of(m) == ENPASSANT;
370 inline Piece Position::captured_piece() const {
371 return st->capturedPiece;
374 inline Thread* Position::this_thread() const {
378 inline void Position::put_piece(Piece pc, Square s) {
381 byTypeBB[ALL_PIECES] |= s;
382 byTypeBB[type_of(pc)] |= s;
383 byColorBB[color_of(pc)] |= s;
384 index[s] = pieceCount[pc]++;
385 pieceList[pc][index[s]] = s;
386 pieceCount[make_piece(color_of(pc), ALL_PIECES)]++;
389 inline void Position::remove_piece(Piece pc, Square s) {
391 // WARNING: This is not a reversible operation. If we remove a piece in
392 // do_move() and then replace it in undo_move() we will put it at the end of
393 // the list and not in its original place, it means index[] and pieceList[]
394 // are not invariant to a do_move() + undo_move() sequence.
395 byTypeBB[ALL_PIECES] ^= s;
396 byTypeBB[type_of(pc)] ^= s;
397 byColorBB[color_of(pc)] ^= s;
398 /* board[s] = NO_PIECE; Not needed, overwritten by the capturing one */
399 Square lastSquare = pieceList[pc][--pieceCount[pc]];
400 index[lastSquare] = index[s];
401 pieceList[pc][index[lastSquare]] = lastSquare;
402 pieceList[pc][pieceCount[pc]] = SQ_NONE;
403 pieceCount[make_piece(color_of(pc), ALL_PIECES)]--;
406 inline void Position::move_piece(Piece pc, Square from, Square to) {
408 // index[from] is not updated and becomes stale. This works as long as index[]
409 // is accessed just by known occupied squares.
410 Bitboard from_to_bb = SquareBB[from] ^ SquareBB[to];
411 byTypeBB[ALL_PIECES] ^= from_to_bb;
412 byTypeBB[type_of(pc)] ^= from_to_bb;
413 byColorBB[color_of(pc)] ^= from_to_bb;
414 board[from] = NO_PIECE;
416 index[to] = index[from];
417 pieceList[pc][index[to]] = to;
420 inline void Position::do_move(Move m, StateInfo& newSt) {
421 do_move(m, newSt, gives_check(m));
424 #endif // #ifndef POSITION_H_INCLUDED