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
25 #include <cstddef> // For offsetof()
27 #include <memory> // For std::unique_ptr
39 extern Score psq[PIECE_NB][SQUARE_NB];
45 /// StateInfo struct stores information needed to restore a Position object to
46 /// its previous state when we retract a move. Whenever a move is made on the
47 /// board (by calling Position::do_move), a StateInfo object must be passed.
51 // Copied when making a move
54 Value nonPawnMaterial[COLOR_NB];
61 // Not copied when making a move
66 Bitboard blockersForKing[COLOR_NB];
67 Bitboard checkSquares[PIECE_TYPE_NB];
70 // In a std::deque references to elements are unaffected upon resizing
71 typedef std::unique_ptr<std::deque<StateInfo>> StateListPtr;
74 /// Position class stores information regarding the board representation as
75 /// pieces, side to move, hash keys, castling info, etc. Important methods are
76 /// do_move() and undo_move(), used by the search to update node info when
77 /// traversing the search tree.
85 Position(const Position&) = delete;
86 Position& operator=(const Position&) = delete;
88 // FEN string input/output
89 Position& set(const std::string& fenStr, bool isChess960, StateInfo* si, Thread* th);
90 const std::string fen() const;
92 // Position representation
93 Bitboard pieces() const;
94 Bitboard pieces(PieceType pt) const;
95 Bitboard pieces(PieceType pt1, PieceType pt2) const;
96 Bitboard pieces(Color c) const;
97 Bitboard pieces(Color c, PieceType pt) const;
98 Bitboard pieces(Color c, PieceType pt1, PieceType pt2) const;
99 Piece piece_on(Square s) const;
100 Square ep_square() const;
101 bool empty(Square s) const;
102 template<PieceType Pt> int count(Color c) const;
103 template<PieceType Pt> const Square* squares(Color c) const;
104 template<PieceType Pt> Square square(Color c) const;
107 int can_castle(Color c) const;
108 int can_castle(CastlingRight cr) const;
109 bool castling_impeded(CastlingRight cr) const;
110 Square castling_rook_square(CastlingRight cr) const;
113 Bitboard checkers() const;
114 Bitboard discovered_check_candidates() const;
115 Bitboard pinned_pieces(Color c) const;
116 Bitboard check_squares(PieceType pt) 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;
124 Bitboard slider_blockers(Bitboard sliders, Square s) const;
126 // Properties of moves
127 bool legal(Move m) const;
128 bool pseudo_legal(const Move m) const;
129 bool capture(Move m) const;
130 bool capture_or_promotion(Move m) const;
131 bool gives_check(Move m) const;
132 bool advanced_pawn_push(Move m) const;
133 Piece moved_piece(Move m) const;
134 Piece captured_piece() const;
137 bool pawn_passed(Color c, Square s) 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 material_key() const;
154 Key pawn_key() const;
156 // Other properties of the position
157 Color side_to_move() const;
158 Phase game_phase() const;
159 int game_ply() const;
160 bool is_chess960() const;
161 Thread* this_thread() const;
162 uint64_t nodes_searched() const;
163 void set_nodes_searched(uint64_t n);
164 bool is_draw() const;
165 int rule50_count() const;
166 Score psq_score() const;
167 Value non_pawn_material(Color c) const;
169 // Position consistency check, for debugging
170 bool pos_is_ok(int* failedStep = nullptr) const;
174 // Initialization helpers (used while setting up a position)
175 void set_castling_right(Color c, Square rfrom);
176 void set_state(StateInfo* si) const;
177 void set_check_info(StateInfo* si) const;
180 void put_piece(Piece pc, Square s);
181 void remove_piece(Piece pc, Square s);
182 void move_piece(Piece pc, Square from, Square to);
184 void do_castling(Color us, Square from, Square& to, Square& rfrom, Square& rto);
187 Piece board[SQUARE_NB];
188 Bitboard byTypeBB[PIECE_TYPE_NB];
189 Bitboard byColorBB[COLOR_NB];
190 int pieceCount[PIECE_NB];
191 Square pieceList[PIECE_NB][16];
192 int index[SQUARE_NB];
193 int castlingRightsMask[SQUARE_NB];
194 Square castlingRookSquare[CASTLING_RIGHT_NB];
195 Bitboard castlingPath[CASTLING_RIGHT_NB];
204 extern std::ostream& operator<<(std::ostream& os, const Position& pos);
206 inline Color Position::side_to_move() const {
210 inline bool Position::empty(Square s) const {
211 return board[s] == NO_PIECE;
214 inline Piece Position::piece_on(Square s) const {
218 inline Piece Position::moved_piece(Move m) const {
219 return board[from_sq(m)];
222 inline Bitboard Position::pieces() const {
223 return byTypeBB[ALL_PIECES];
226 inline Bitboard Position::pieces(PieceType pt) const {
230 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2) const {
231 return byTypeBB[pt1] | byTypeBB[pt2];
234 inline Bitboard Position::pieces(Color c) const {
238 inline Bitboard Position::pieces(Color c, PieceType pt) const {
239 return byColorBB[c] & byTypeBB[pt];
242 inline Bitboard Position::pieces(Color c, PieceType pt1, PieceType pt2) const {
243 return byColorBB[c] & (byTypeBB[pt1] | byTypeBB[pt2]);
246 template<PieceType Pt> inline int Position::count(Color c) const {
247 return pieceCount[make_piece(c, Pt)];
250 template<PieceType Pt> inline const Square* Position::squares(Color c) const {
251 return pieceList[make_piece(c, Pt)];
254 template<PieceType Pt> inline Square Position::square(Color c) const {
255 assert(pieceCount[make_piece(c, Pt)] == 1);
256 return pieceList[make_piece(c, Pt)][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 st->blockersForKing[~sideToMove] & pieces(sideToMove);
307 inline Bitboard Position::pinned_pieces(Color c) const {
308 return st->blockersForKing[c] & pieces(c);
311 inline Bitboard Position::check_squares(PieceType pt) const {
312 return st->checkSquares[pt];
315 inline bool Position::pawn_passed(Color c, Square s) const {
316 return !(pieces(~c, PAWN) & passed_pawn_mask(c, s));
319 inline bool Position::advanced_pawn_push(Move m) const {
320 return type_of(moved_piece(m)) == PAWN
321 && relative_rank(sideToMove, from_sq(m)) > RANK_4;
324 inline Key Position::key() const {
328 inline Key Position::pawn_key() const {
332 inline Key Position::material_key() const {
333 return st->materialKey;
336 inline Score Position::psq_score() const {
340 inline Value Position::non_pawn_material(Color c) const {
341 return st->nonPawnMaterial[c];
344 inline int Position::game_ply() const {
348 inline int Position::rule50_count() const {
352 inline uint64_t Position::nodes_searched() const {
356 inline void Position::set_nodes_searched(uint64_t n) {
360 inline bool Position::opposite_bishops() const {
361 return pieceCount[W_BISHOP] == 1
362 && pieceCount[B_BISHOP] == 1
363 && opposite_colors(square<BISHOP>(WHITE), square<BISHOP>(BLACK));
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 Piece Position::captured_piece() const {
384 return st->capturedPiece;
387 inline Thread* Position::this_thread() const {
391 inline void Position::put_piece(Piece pc, Square s) {
394 byTypeBB[ALL_PIECES] |= s;
395 byTypeBB[type_of(pc)] |= s;
396 byColorBB[color_of(pc)] |= s;
397 index[s] = pieceCount[pc]++;
398 pieceList[pc][index[s]] = s;
399 pieceCount[make_piece(color_of(pc), ALL_PIECES)]++;
402 inline void Position::remove_piece(Piece pc, 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;
409 byTypeBB[type_of(pc)] ^= s;
410 byColorBB[color_of(pc)] ^= s;
411 /* board[s] = NO_PIECE; Not needed, overwritten by the capturing one */
412 Square lastSquare = pieceList[pc][--pieceCount[pc]];
413 index[lastSquare] = index[s];
414 pieceList[pc][index[lastSquare]] = lastSquare;
415 pieceList[pc][pieceCount[pc]] = SQ_NONE;
416 pieceCount[make_piece(color_of(pc), ALL_PIECES)]--;
419 inline void Position::move_piece(Piece pc, 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[type_of(pc)] ^= from_to_bb;
426 byColorBB[color_of(pc)] ^= from_to_bb;
427 board[from] = NO_PIECE;
429 index[to] = index[from];
430 pieceList[pc][index[to]] = to;
433 #endif // #ifndef POSITION_H_INCLUDED