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) 2015-2017 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 Position& set(const std::string& code, Color c, StateInfo* si);
80 const std::string fen() const;
82 // Position representation
83 Bitboard pieces() const;
84 Bitboard pieces(PieceType pt) const;
85 Bitboard pieces(PieceType pt1, PieceType pt2) const;
86 Bitboard pieces(Color c) const;
87 Bitboard pieces(Color c, PieceType pt) const;
88 Bitboard pieces(Color c, PieceType pt1, PieceType pt2) const;
89 Piece piece_on(Square s) const;
90 Square ep_square() const;
91 bool empty(Square s) const;
92 template<PieceType Pt> int count(Color c) const;
93 template<PieceType Pt> int count() const;
94 template<PieceType Pt> const Square* squares(Color c) const;
95 template<PieceType Pt> Square square(Color c) const;
98 int can_castle(Color c) const;
99 int can_castle(CastlingRight cr) const;
100 bool castling_impeded(CastlingRight cr) const;
101 Square castling_rook_square(CastlingRight cr) const;
104 Bitboard checkers() const;
105 Bitboard discovered_check_candidates() const;
106 Bitboard pinned_pieces(Color c) const;
107 Bitboard check_squares(PieceType pt) const;
109 // Attacks to/from a given square
110 Bitboard attackers_to(Square s) const;
111 Bitboard attackers_to(Square s, Bitboard occupied) const;
112 Bitboard attacks_from(Piece pc, Square s) const;
113 template<PieceType> Bitboard attacks_from(Square s) const;
114 template<PieceType> Bitboard attacks_from(Square s, Color c) const;
115 Bitboard slider_blockers(Bitboard sliders, Square s, Bitboard& pinners) const;
117 // Properties of moves
118 bool legal(Move m) const;
119 bool pseudo_legal(const Move m) const;
120 bool capture(Move m) const;
121 bool capture_or_promotion(Move m) const;
122 bool gives_check(Move m) const;
123 bool advanced_pawn_push(Move m) const;
124 Piece moved_piece(Move m) const;
125 Piece captured_piece() const;
128 bool pawn_passed(Color c, Square s) const;
129 bool opposite_bishops() const;
131 // Doing and undoing moves
132 void do_move(Move m, StateInfo& newSt);
133 void do_move(Move m, StateInfo& newSt, bool givesCheck);
134 void undo_move(Move m);
135 void do_null_move(StateInfo& newSt);
136 void undo_null_move();
138 // Static Exchange Evaluation
139 bool see_ge(Move m, Value value) const;
141 // Accessing hash keys
143 Key key_after(Move m) const;
144 Key material_key() const;
145 Key pawn_key() const;
147 // Other properties of the position
148 Color side_to_move() const;
149 Phase game_phase() const;
150 int game_ply() const;
151 bool is_chess960() const;
152 Thread* this_thread() const;
153 uint64_t nodes_searched() const;
154 bool is_draw(int ply) const;
155 int rule50_count() const;
156 Score psq_score() const;
157 Value non_pawn_material(Color c) const;
158 Value non_pawn_material() const;
160 // Position consistency check, for debugging
161 bool pos_is_ok(int* failedStep = nullptr) const;
165 // Initialization helpers (used while setting up a position)
166 void set_castling_right(Color c, Square rfrom);
167 void set_state(StateInfo* si) const;
168 void set_check_info(StateInfo* si) const;
171 void put_piece(Piece pc, Square s);
172 void remove_piece(Piece pc, Square s);
173 void move_piece(Piece pc, Square from, Square to);
175 void do_castling(Color us, Square from, Square& to, Square& rfrom, Square& rto);
178 Piece board[SQUARE_NB];
179 Bitboard byTypeBB[PIECE_TYPE_NB];
180 Bitboard byColorBB[COLOR_NB];
181 int pieceCount[PIECE_NB];
182 Square pieceList[PIECE_NB][16];
183 int index[SQUARE_NB];
184 int castlingRightsMask[SQUARE_NB];
185 Square castlingRookSquare[CASTLING_RIGHT_NB];
186 Bitboard castlingPath[CASTLING_RIGHT_NB];
195 extern std::ostream& operator<<(std::ostream& os, const Position& pos);
197 inline Color Position::side_to_move() const {
201 inline bool Position::empty(Square s) const {
202 return board[s] == NO_PIECE;
205 inline Piece Position::piece_on(Square s) const {
209 inline Piece Position::moved_piece(Move m) const {
210 return board[from_sq(m)];
213 inline Bitboard Position::pieces() const {
214 return byTypeBB[ALL_PIECES];
217 inline Bitboard Position::pieces(PieceType pt) const {
221 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2) const {
222 return byTypeBB[pt1] | byTypeBB[pt2];
225 inline Bitboard Position::pieces(Color c) const {
229 inline Bitboard Position::pieces(Color c, PieceType pt) const {
230 return byColorBB[c] & byTypeBB[pt];
233 inline Bitboard Position::pieces(Color c, PieceType pt1, PieceType pt2) const {
234 return byColorBB[c] & (byTypeBB[pt1] | byTypeBB[pt2]);
237 template<PieceType Pt> inline int Position::count(Color c) const {
238 return pieceCount[make_piece(c, Pt)];
241 template<PieceType Pt> inline int Position::count() const {
242 return pieceCount[make_piece(WHITE, Pt)] + pieceCount[make_piece(BLACK, Pt)];
245 template<PieceType Pt> inline const Square* Position::squares(Color c) const {
246 return pieceList[make_piece(c, Pt)];
249 template<PieceType Pt> inline Square Position::square(Color c) const {
250 assert(pieceCount[make_piece(c, Pt)] == 1);
251 return pieceList[make_piece(c, Pt)][0];
254 inline Square Position::ep_square() const {
258 inline int Position::can_castle(CastlingRight cr) const {
259 return st->castlingRights & cr;
262 inline int Position::can_castle(Color c) const {
263 return st->castlingRights & ((WHITE_OO | WHITE_OOO) << (2 * c));
266 inline bool Position::castling_impeded(CastlingRight cr) const {
267 return byTypeBB[ALL_PIECES] & castlingPath[cr];
270 inline Square Position::castling_rook_square(CastlingRight cr) const {
271 return castlingRookSquare[cr];
274 template<PieceType Pt>
275 inline Bitboard Position::attacks_from(Square s) const {
277 return Pt == BISHOP || Pt == ROOK ? attacks_bb<Pt>(s, byTypeBB[ALL_PIECES])
278 : Pt == QUEEN ? attacks_from<ROOK>(s) | attacks_from<BISHOP>(s)
279 : StepAttacksBB[Pt][s];
283 inline Bitboard Position::attacks_from<PAWN>(Square s, Color c) const {
284 return StepAttacksBB[make_piece(c, PAWN)][s];
287 inline Bitboard Position::attacks_from(Piece pc, Square s) const {
288 return attacks_bb(pc, s, byTypeBB[ALL_PIECES]);
291 inline Bitboard Position::attackers_to(Square s) const {
292 return attackers_to(s, byTypeBB[ALL_PIECES]);
295 inline Bitboard Position::checkers() const {
296 return st->checkersBB;
299 inline Bitboard Position::discovered_check_candidates() const {
300 return st->blockersForKing[~sideToMove] & pieces(sideToMove);
303 inline Bitboard Position::pinned_pieces(Color c) const {
304 return st->blockersForKing[c] & pieces(c);
307 inline Bitboard Position::check_squares(PieceType pt) const {
308 return st->checkSquares[pt];
311 inline bool Position::pawn_passed(Color c, Square s) const {
312 return !(pieces(~c, PAWN) & passed_pawn_mask(c, s));
315 inline bool Position::advanced_pawn_push(Move m) const {
316 return type_of(moved_piece(m)) == PAWN
317 && relative_rank(sideToMove, from_sq(m)) > RANK_4;
320 inline Key Position::key() const {
324 inline Key Position::pawn_key() const {
328 inline Key Position::material_key() const {
329 return st->materialKey;
332 inline Score Position::psq_score() const {
336 inline Value Position::non_pawn_material(Color c) const {
337 return st->nonPawnMaterial[c];
340 inline Value Position::non_pawn_material() const {
341 return st->nonPawnMaterial[WHITE] + st->nonPawnMaterial[BLACK];
344 inline int Position::game_ply() const {
348 inline int Position::rule50_count() const {
352 inline uint64_t Position::nodes_searched() const {
356 inline bool Position::opposite_bishops() const {
357 return pieceCount[W_BISHOP] == 1
358 && pieceCount[B_BISHOP] == 1
359 && opposite_colors(square<BISHOP>(WHITE), square<BISHOP>(BLACK));
362 inline bool Position::is_chess960() const {
366 inline bool Position::capture_or_promotion(Move m) const {
368 return type_of(m) != NORMAL ? type_of(m) != CASTLING : !empty(to_sq(m));
371 inline bool Position::capture(Move m) const {
373 // Castling is encoded as "king captures rook"
374 return (!empty(to_sq(m)) && type_of(m) != CASTLING) || type_of(m) == ENPASSANT;
377 inline Piece Position::captured_piece() const {
378 return st->capturedPiece;
381 inline Thread* Position::this_thread() const {
385 inline void Position::put_piece(Piece pc, Square s) {
388 byTypeBB[ALL_PIECES] |= s;
389 byTypeBB[type_of(pc)] |= s;
390 byColorBB[color_of(pc)] |= s;
391 index[s] = pieceCount[pc]++;
392 pieceList[pc][index[s]] = s;
393 pieceCount[make_piece(color_of(pc), ALL_PIECES)]++;
396 inline void Position::remove_piece(Piece pc, Square s) {
398 // WARNING: This is not a reversible operation. If we remove a piece in
399 // do_move() and then replace it in undo_move() we will put it at the end of
400 // the list and not in its original place, it means index[] and pieceList[]
401 // are not invariant to a do_move() + undo_move() sequence.
402 byTypeBB[ALL_PIECES] ^= s;
403 byTypeBB[type_of(pc)] ^= s;
404 byColorBB[color_of(pc)] ^= s;
405 /* board[s] = NO_PIECE; Not needed, overwritten by the capturing one */
406 Square lastSquare = pieceList[pc][--pieceCount[pc]];
407 index[lastSquare] = index[s];
408 pieceList[pc][index[lastSquare]] = lastSquare;
409 pieceList[pc][pieceCount[pc]] = SQ_NONE;
410 pieceCount[make_piece(color_of(pc), ALL_PIECES)]--;
413 inline void Position::move_piece(Piece pc, Square from, Square to) {
415 // index[from] is not updated and becomes stale. This works as long as index[]
416 // is accessed just by known occupied squares.
417 Bitboard from_to_bb = SquareBB[from] ^ SquareBB[to];
418 byTypeBB[ALL_PIECES] ^= from_to_bb;
419 byTypeBB[type_of(pc)] ^= from_to_bb;
420 byColorBB[color_of(pc)] ^= from_to_bb;
421 board[from] = NO_PIECE;
423 index[to] = index[from];
424 pieceList[pc][index[to]] = to;
427 inline void Position::do_move(Move m, StateInfo& newSt) {
428 do_move(m, newSt, gives_check(m));
431 #endif // #ifndef POSITION_H_INCLUDED