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 Value see(Move m) const;
137 Value see_sign(Move m) const;
139 // Accessing hash keys
141 Key key_after(Move m) const;
142 Key material_key() const;
143 Key pawn_key() const;
145 // Other properties of the position
146 Color side_to_move() const;
147 Phase game_phase() const;
148 int game_ply() const;
149 bool is_chess960() const;
150 Thread* this_thread() const;
151 uint64_t nodes_searched() const;
152 void set_nodes_searched(uint64_t n);
153 bool is_draw() const;
154 int rule50_count() const;
155 Score psq_score() const;
156 Value non_pawn_material(Color c) const;
158 // Position consistency check, for debugging
159 bool pos_is_ok(int* failedStep = nullptr) const;
163 // Initialization helpers (used while setting up a position)
164 void set_castling_right(Color c, Square rfrom);
165 void set_state(StateInfo* si) const;
166 void set_check_info(StateInfo* si) const;
169 void put_piece(Piece pc, Square s);
170 void remove_piece(Piece pc, Square s);
171 void move_piece(Piece pc, Square from, Square to);
173 void do_castling(Color us, Square from, Square& to, Square& rfrom, Square& rto);
176 Piece board[SQUARE_NB];
177 Bitboard byTypeBB[PIECE_TYPE_NB];
178 Bitboard byColorBB[COLOR_NB];
179 int pieceCount[PIECE_NB];
180 Square pieceList[PIECE_NB][16];
181 int index[SQUARE_NB];
182 int castlingRightsMask[SQUARE_NB];
183 Square castlingRookSquare[CASTLING_RIGHT_NB];
184 Bitboard castlingPath[CASTLING_RIGHT_NB];
193 extern std::ostream& operator<<(std::ostream& os, const Position& pos);
195 inline Color Position::side_to_move() const {
199 inline bool Position::empty(Square s) const {
200 return board[s] == NO_PIECE;
203 inline Piece Position::piece_on(Square s) const {
207 inline Piece Position::moved_piece(Move m) const {
208 return board[from_sq(m)];
211 inline Bitboard Position::pieces() const {
212 return byTypeBB[ALL_PIECES];
215 inline Bitboard Position::pieces(PieceType pt) const {
219 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2) const {
220 return byTypeBB[pt1] | byTypeBB[pt2];
223 inline Bitboard Position::pieces(Color c) const {
227 inline Bitboard Position::pieces(Color c, PieceType pt) const {
228 return byColorBB[c] & byTypeBB[pt];
231 inline Bitboard Position::pieces(Color c, PieceType pt1, PieceType pt2) const {
232 return byColorBB[c] & (byTypeBB[pt1] | byTypeBB[pt2]);
235 template<PieceType Pt> inline int Position::count(Color c) const {
236 return pieceCount[make_piece(c, Pt)];
239 template<PieceType Pt> inline const Square* Position::squares(Color c) const {
240 return pieceList[make_piece(c, Pt)];
243 template<PieceType Pt> inline Square Position::square(Color c) const {
244 assert(pieceCount[make_piece(c, Pt)] == 1);
245 return pieceList[make_piece(c, Pt)][0];
248 inline Square Position::ep_square() const {
252 inline int Position::can_castle(CastlingRight cr) const {
253 return st->castlingRights & cr;
256 inline int Position::can_castle(Color c) const {
257 return st->castlingRights & ((WHITE_OO | WHITE_OOO) << (2 * c));
260 inline bool Position::castling_impeded(CastlingRight cr) const {
261 return byTypeBB[ALL_PIECES] & castlingPath[cr];
264 inline Square Position::castling_rook_square(CastlingRight cr) const {
265 return castlingRookSquare[cr];
268 template<PieceType Pt>
269 inline Bitboard Position::attacks_from(Square s) const {
270 return Pt == BISHOP || Pt == ROOK ? attacks_bb<Pt>(s, byTypeBB[ALL_PIECES])
271 : Pt == QUEEN ? attacks_from<ROOK>(s) | attacks_from<BISHOP>(s)
272 : StepAttacksBB[Pt][s];
276 inline Bitboard Position::attacks_from<PAWN>(Square s, Color c) const {
277 return StepAttacksBB[make_piece(c, PAWN)][s];
280 inline Bitboard Position::attacks_from(Piece pc, Square s) const {
281 return attacks_bb(pc, s, byTypeBB[ALL_PIECES]);
284 inline Bitboard Position::attackers_to(Square s) const {
285 return attackers_to(s, byTypeBB[ALL_PIECES]);
288 inline Bitboard Position::checkers() const {
289 return st->checkersBB;
292 inline Bitboard Position::discovered_check_candidates() const {
293 return st->blockersForKing[~sideToMove] & pieces(sideToMove);
296 inline Bitboard Position::pinned_pieces(Color c) const {
297 return st->blockersForKing[c] & pieces(c);
300 inline Bitboard Position::check_squares(PieceType pt) const {
301 return st->checkSquares[pt];
304 inline bool Position::pawn_passed(Color c, Square s) const {
305 return !(pieces(~c, PAWN) & passed_pawn_mask(c, s));
308 inline bool Position::advanced_pawn_push(Move m) const {
309 return type_of(moved_piece(m)) == PAWN
310 && relative_rank(sideToMove, from_sq(m)) > RANK_4;
313 inline Key Position::key() const {
317 inline Key Position::pawn_key() const {
321 inline Key Position::material_key() const {
322 return st->materialKey;
325 inline Score Position::psq_score() const {
329 inline Value Position::non_pawn_material(Color c) const {
330 return st->nonPawnMaterial[c];
333 inline int Position::game_ply() const {
337 inline int Position::rule50_count() const {
341 inline uint64_t Position::nodes_searched() const {
345 inline void Position::set_nodes_searched(uint64_t n) {
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 #endif // #ifndef POSITION_H_INCLUDED