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) 2015-2019 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];
48 // Not copied when making a move (will be recomputed anyhow)
53 Bitboard blockersForKing[COLOR_NB];
54 Bitboard pinners[COLOR_NB];
55 Bitboard checkSquares[PIECE_TYPE_NB];
58 /// A list to keep track of the position states along the setup moves (from the
59 /// start position to the position just before the search starts). Needed by
60 /// 'draw by repetition' detection. Use a std::deque because pointers to
61 /// elements are not invalidated upon list resizing.
62 typedef std::unique_ptr<std::deque<StateInfo>> StateListPtr;
65 /// Position class stores information regarding the board representation as
66 /// pieces, side to move, hash keys, castling info, etc. Important methods are
67 /// do_move() and undo_move(), used by the search to update node info when
68 /// traversing the search tree.
76 Position(const Position&) = delete;
77 Position& operator=(const Position&) = delete;
79 // FEN string input/output
80 Position& set(const std::string& fenStr, bool isChess960, StateInfo* si, Thread* th);
81 Position& set(const std::string& code, Color c, StateInfo* si);
82 const std::string fen() const;
84 // Position representation
85 Bitboard pieces() const;
86 Bitboard pieces(PieceType pt) const;
87 Bitboard pieces(PieceType pt1, PieceType pt2) const;
88 Bitboard pieces(Color c) const;
89 Bitboard pieces(Color c, PieceType pt) const;
90 Bitboard pieces(Color c, PieceType pt1, PieceType pt2) const;
91 Piece piece_on(Square s) const;
92 Square ep_square() const;
93 bool empty(Square s) const;
94 template<PieceType Pt> int count(Color c) const;
95 template<PieceType Pt> int count() const;
96 template<PieceType Pt> const Square* squares(Color c) const;
97 template<PieceType Pt> Square square(Color c) const;
100 int can_castle(Color c) const;
101 int can_castle(CastlingRight cr) const;
102 bool castling_impeded(CastlingRight cr) const;
103 Square castling_rook_square(CastlingRight cr) const;
106 Bitboard checkers() const;
107 Bitboard blockers_for_king(Color c) const;
108 Bitboard check_squares(PieceType pt) const;
110 // Attacks to/from a given square
111 Bitboard attackers_to(Square s) const;
112 Bitboard attackers_to(Square s, Bitboard occupied) const;
113 Bitboard attacks_from(PieceType pt, Square s) const;
114 template<PieceType> Bitboard attacks_from(Square s) const;
115 template<PieceType> Bitboard attacks_from(Square s, Color c) const;
116 Bitboard slider_blockers(Bitboard sliders, Square s, Bitboard& pinners) const;
118 // Properties of moves
119 bool legal(Move m) const;
120 bool pseudo_legal(const Move m) const;
121 bool capture(Move m) const;
122 bool capture_or_promotion(Move m) const;
123 bool gives_check(Move m) const;
124 bool advanced_pawn_push(Move m) const;
125 Piece moved_piece(Move m) const;
126 Piece captured_piece() const;
129 bool pawn_passed(Color c, Square s) const;
130 bool opposite_bishops() const;
132 // Doing and undoing moves
133 void do_move(Move m, StateInfo& newSt);
134 void do_move(Move m, StateInfo& newSt, bool givesCheck);
135 void undo_move(Move m);
136 void do_null_move(StateInfo& newSt);
137 void undo_null_move();
139 // Static Exchange Evaluation
140 bool see_ge(Move m, Value threshold = VALUE_ZERO) const;
142 // Accessing hash keys
144 Key key_after(Move m) const;
145 Key material_key() const;
146 Key pawn_key() const;
148 // Other properties of the position
149 Color side_to_move() const;
150 int game_ply() const;
151 bool is_chess960() const;
152 Thread* this_thread() const;
153 bool is_draw(int ply) const;
154 bool has_game_cycle(int ply) const;
155 bool has_repeated() const;
156 int rule50_count() const;
157 Score psq_score() const;
158 Value non_pawn_material(Color c) const;
159 Value non_pawn_material() const;
161 // Position consistency check, for debugging
162 bool pos_is_ok() const;
166 // Initialization helpers (used while setting up a position)
167 void set_castling_right(Color c, Square rfrom);
168 void set_state(StateInfo* si) const;
169 void set_check_info(StateInfo* si) const;
172 void put_piece(Piece pc, Square s);
173 void remove_piece(Piece pc, Square s);
174 void move_piece(Piece pc, Square from, Square to);
176 void do_castling(Color us, Square from, Square& to, Square& rfrom, Square& rto);
179 Piece board[SQUARE_NB];
180 Bitboard byTypeBB[PIECE_TYPE_NB];
181 Bitboard byColorBB[COLOR_NB];
182 int pieceCount[PIECE_NB];
183 Square pieceList[PIECE_NB][16];
184 int index[SQUARE_NB];
185 int castlingRightsMask[SQUARE_NB];
186 Square castlingRookSquare[CASTLING_RIGHT_NB];
187 Bitboard castlingPath[CASTLING_RIGHT_NB];
197 extern Score psq[PIECE_NB][SQUARE_NB];
200 extern std::ostream& operator<<(std::ostream& os, const Position& pos);
202 inline Color Position::side_to_move() const {
206 inline bool Position::empty(Square s) const {
207 return board[s] == NO_PIECE;
210 inline Piece Position::piece_on(Square s) const {
214 inline Piece Position::moved_piece(Move m) const {
215 return board[from_sq(m)];
218 inline Bitboard Position::pieces() const {
219 return byTypeBB[ALL_PIECES];
222 inline Bitboard Position::pieces(PieceType pt) const {
226 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2) const {
227 return byTypeBB[pt1] | byTypeBB[pt2];
230 inline Bitboard Position::pieces(Color c) const {
234 inline Bitboard Position::pieces(Color c, PieceType pt) const {
235 return byColorBB[c] & byTypeBB[pt];
238 inline Bitboard Position::pieces(Color c, PieceType pt1, PieceType pt2) const {
239 return byColorBB[c] & (byTypeBB[pt1] | byTypeBB[pt2]);
242 template<PieceType Pt> inline int Position::count(Color c) const {
243 return pieceCount[make_piece(c, Pt)];
246 template<PieceType Pt> inline int Position::count() const {
247 return pieceCount[make_piece(WHITE, Pt)] + pieceCount[make_piece(BLACK, 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 {
282 return Pt == BISHOP || Pt == ROOK ? attacks_bb<Pt>(s, byTypeBB[ALL_PIECES])
283 : Pt == QUEEN ? attacks_from<ROOK>(s) | attacks_from<BISHOP>(s)
284 : PseudoAttacks[Pt][s];
288 inline Bitboard Position::attacks_from<PAWN>(Square s, Color c) const {
289 return PawnAttacks[c][s];
292 inline Bitboard Position::attacks_from(PieceType pt, Square s) const {
293 return attacks_bb(pt, s, byTypeBB[ALL_PIECES]);
296 inline Bitboard Position::attackers_to(Square s) const {
297 return attackers_to(s, byTypeBB[ALL_PIECES]);
300 inline Bitboard Position::checkers() const {
301 return st->checkersBB;
304 inline Bitboard Position::blockers_for_king(Color c) const {
305 return st->blockersForKing[c];
308 inline Bitboard Position::check_squares(PieceType pt) const {
309 return st->checkSquares[pt];
312 inline bool Position::pawn_passed(Color c, Square s) const {
313 return !(pieces(~c, PAWN) & passed_pawn_mask(c, s));
316 inline bool Position::advanced_pawn_push(Move m) const {
317 return type_of(moved_piece(m)) == PAWN
318 && relative_rank(sideToMove, from_sq(m)) > RANK_4;
321 inline Key Position::key() const {
325 inline Key Position::pawn_key() const {
329 inline Key Position::material_key() const {
330 return st->materialKey;
333 inline Score Position::psq_score() const {
337 inline Value Position::non_pawn_material(Color c) const {
338 return st->nonPawnMaterial[c];
341 inline Value Position::non_pawn_material() const {
342 return st->nonPawnMaterial[WHITE] + st->nonPawnMaterial[BLACK];
345 inline int Position::game_ply() const {
349 inline int Position::rule50_count() const {
353 inline bool Position::opposite_bishops() const {
354 return pieceCount[W_BISHOP] == 1
355 && pieceCount[B_BISHOP] == 1
356 && opposite_colors(square<BISHOP>(WHITE), square<BISHOP>(BLACK));
359 inline bool Position::is_chess960() const {
363 inline bool Position::capture_or_promotion(Move m) const {
365 return type_of(m) != NORMAL ? type_of(m) != CASTLING : !empty(to_sq(m));
368 inline bool Position::capture(Move m) const {
370 // Castling is encoded as "king captures rook"
371 return (!empty(to_sq(m)) && type_of(m) != CASTLING) || type_of(m) == ENPASSANT;
374 inline Piece Position::captured_piece() const {
375 return st->capturedPiece;
378 inline Thread* Position::this_thread() const {
382 inline void Position::put_piece(Piece pc, Square s) {
385 byTypeBB[ALL_PIECES] |= s;
386 byTypeBB[type_of(pc)] |= s;
387 byColorBB[color_of(pc)] |= s;
388 index[s] = pieceCount[pc]++;
389 pieceList[pc][index[s]] = s;
390 pieceCount[make_piece(color_of(pc), ALL_PIECES)]++;
391 psq += PSQT::psq[pc][s];
394 inline void Position::remove_piece(Piece pc, Square s) {
396 // WARNING: This is not a reversible operation. If we remove a piece in
397 // do_move() and then replace it in undo_move() we will put it at the end of
398 // the list and not in its original place, it means index[] and pieceList[]
399 // are not invariant to a do_move() + undo_move() sequence.
400 byTypeBB[ALL_PIECES] ^= s;
401 byTypeBB[type_of(pc)] ^= s;
402 byColorBB[color_of(pc)] ^= s;
403 /* board[s] = NO_PIECE; Not needed, overwritten by the capturing one */
404 Square lastSquare = pieceList[pc][--pieceCount[pc]];
405 index[lastSquare] = index[s];
406 pieceList[pc][index[lastSquare]] = lastSquare;
407 pieceList[pc][pieceCount[pc]] = SQ_NONE;
408 pieceCount[make_piece(color_of(pc), ALL_PIECES)]--;
409 psq -= PSQT::psq[pc][s];
412 inline void Position::move_piece(Piece pc, Square from, Square to) {
414 // index[from] is not updated and becomes stale. This works as long as index[]
415 // is accessed just by known occupied squares.
416 Bitboard fromTo = SquareBB[from] ^ SquareBB[to];
417 byTypeBB[ALL_PIECES] ^= fromTo;
418 byTypeBB[type_of(pc)] ^= fromTo;
419 byColorBB[color_of(pc)] ^= fromTo;
420 board[from] = NO_PIECE;
422 index[to] = index[from];
423 pieceList[pc][index[to]] = to;
424 psq += PSQT::psq[pc][to] - PSQT::psq[pc][from];
427 inline void Position::do_move(Move m, StateInfo& newSt) {
428 do_move(m, newSt, gives_check(m));
431 #endif // #ifndef POSITION_H_INCLUDED