2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2021 The Stockfish developers (see AUTHORS file)
5 Stockfish is free software: you can redistribute it and/or modify
6 it under the terms of the GNU General Public License as published by
7 the Free Software Foundation, either version 3 of the License, or
8 (at your option) any later version.
10 Stockfish is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 GNU General Public License for more details.
15 You should have received a copy of the GNU General Public License
16 along with this program. If not, see <http://www.gnu.org/licenses/>.
19 #ifndef POSITION_H_INCLUDED
20 #define POSITION_H_INCLUDED
24 #include <memory> // For std::unique_ptr
32 #include "nnue/nnue_accumulator.h"
36 /// StateInfo struct stores information needed to restore a Position object to
37 /// its previous state when we retract a move. Whenever a move is made on the
38 /// board (by calling Position::do_move), a StateInfo object must be passed.
42 // Copied when making a move
45 Value nonPawnMaterial[COLOR_NB];
51 // Not copied when making a move (will be recomputed anyhow)
56 Bitboard blockersForKing[COLOR_NB];
57 Bitboard pinners[COLOR_NB];
58 Bitboard checkSquares[PIECE_TYPE_NB];
62 Eval::NNUE::Accumulator accumulator;
63 DirtyPiece dirtyPiece;
67 /// A list to keep track of the position states along the setup moves (from the
68 /// start position to the position just before the search starts). Needed by
69 /// 'draw by repetition' detection. Use a std::deque because pointers to
70 /// elements are not invalidated upon list 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 Position& set(const std::string& code, Color c, StateInfo* si);
91 std::string fen() const;
93 // Position representation
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> int count() const;
104 template<PieceType Pt> Square square(Color c) const;
105 bool is_on_semiopen_file(Color c, Square s) const;
108 CastlingRights castling_rights(Color c) const;
109 bool can_castle(CastlingRights cr) const;
110 bool castling_impeded(CastlingRights cr) const;
111 Square castling_rook_square(CastlingRights cr) const;
114 Bitboard checkers() const;
115 Bitboard blockers_for_king(Color c) const;
116 Bitboard check_squares(PieceType pt) const;
117 Bitboard pinners(Color c) const;
118 bool is_discovered_check_on_king(Color c, Move m) const;
120 // Attacks to/from a given square
121 Bitboard attackers_to(Square s) const;
122 Bitboard attackers_to(Square s, Bitboard occupied) const;
123 Bitboard slider_blockers(Bitboard sliders, Square s, Bitboard& pinners) const;
125 // Properties of moves
126 bool legal(Move m) const;
127 bool pseudo_legal(const Move m) const;
128 bool capture(Move m) const;
129 bool capture_or_promotion(Move m) const;
130 bool gives_check(Move m) const;
131 Piece moved_piece(Move m) const;
132 Piece captured_piece() const;
135 bool pawn_passed(Color c, Square s) const;
136 bool opposite_bishops() const;
137 int pawns_on_same_color_squares(Color c, Square s) const;
139 // Doing and undoing moves
140 void do_move(Move m, StateInfo& newSt);
141 void do_move(Move m, StateInfo& newSt, bool givesCheck);
142 void undo_move(Move m);
143 void do_null_move(StateInfo& newSt);
144 void undo_null_move();
146 // Static Exchange Evaluation
147 bool see_ge(Move m, Value threshold = VALUE_ZERO) const;
149 // Accessing hash keys
151 Key key_after(Move m) const;
152 Key material_key() const;
153 Key pawn_key() const;
155 // Other properties of the position
156 Color side_to_move() const;
157 int game_ply() const;
158 bool is_chess960() const;
159 Thread* this_thread() const;
160 bool is_draw(int ply) const;
161 bool has_game_cycle(int ply) const;
162 bool has_repeated() const;
163 int rule50_count() const;
164 Score psq_score() const;
165 Value non_pawn_material(Color c) const;
166 Value non_pawn_material() const;
168 // Position consistency check, for debugging
169 bool pos_is_ok() const;
173 StateInfo* state() const;
176 // Initialization helpers (used while setting up a position)
177 void set_castling_right(Color c, Square rfrom);
178 void set_state(StateInfo* si) const;
179 void set_check_info(StateInfo* si) const;
182 void put_piece(Piece pc, Square s);
183 void remove_piece(Square s);
184 void move_piece(Square from, Square to);
186 void do_castling(Color us, Square from, Square& to, Square& rfrom, Square& rto);
189 Piece board[SQUARE_NB];
190 Bitboard byTypeBB[PIECE_TYPE_NB];
191 Bitboard byColorBB[COLOR_NB];
192 int pieceCount[PIECE_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 Piece Position::piece_on(Square s) const {
215 inline bool Position::empty(Square s) const {
216 return piece_on(s) == NO_PIECE;
219 inline Piece Position::moved_piece(Move m) const {
220 return piece_on(from_sq(m));
223 inline Bitboard Position::pieces(PieceType pt = ALL_PIECES) const {
227 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2) const {
228 return pieces(pt1) | pieces(pt2);
231 inline Bitboard Position::pieces(Color c) const {
235 inline Bitboard Position::pieces(Color c, PieceType pt) const {
236 return pieces(c) & pieces(pt);
239 inline Bitboard Position::pieces(Color c, PieceType pt1, PieceType pt2) const {
240 return pieces(c) & (pieces(pt1) | pieces(pt2));
243 template<PieceType Pt> inline int Position::count(Color c) const {
244 return pieceCount[make_piece(c, Pt)];
247 template<PieceType Pt> inline int Position::count() const {
248 return count<Pt>(WHITE) + count<Pt>(BLACK);
251 template<PieceType Pt> inline Square Position::square(Color c) const {
252 assert(count<Pt>(c) == 1);
253 return lsb(pieces(c, Pt));
256 inline Square Position::ep_square() const {
260 inline bool Position::is_on_semiopen_file(Color c, Square s) const {
261 return !(pieces(c, PAWN) & file_bb(s));
264 inline bool Position::can_castle(CastlingRights cr) const {
265 return st->castlingRights & cr;
268 inline CastlingRights Position::castling_rights(Color c) const {
269 return c & CastlingRights(st->castlingRights);
272 inline bool Position::castling_impeded(CastlingRights cr) const {
273 assert(cr == WHITE_OO || cr == WHITE_OOO || cr == BLACK_OO || cr == BLACK_OOO);
275 return pieces() & castlingPath[cr];
278 inline Square Position::castling_rook_square(CastlingRights cr) const {
279 assert(cr == WHITE_OO || cr == WHITE_OOO || cr == BLACK_OO || cr == BLACK_OOO);
281 return castlingRookSquare[cr];
284 inline Bitboard Position::attackers_to(Square s) const {
285 return attackers_to(s, pieces());
288 inline Bitboard Position::checkers() const {
289 return st->checkersBB;
292 inline Bitboard Position::blockers_for_king(Color c) const {
293 return st->blockersForKing[c];
296 inline Bitboard Position::pinners(Color c) const {
297 return st->pinners[c];
300 inline Bitboard Position::check_squares(PieceType pt) const {
301 return st->checkSquares[pt];
304 inline bool Position::is_discovered_check_on_king(Color c, Move m) const {
305 return st->blockersForKing[c] & from_sq(m);
308 inline bool Position::pawn_passed(Color c, Square s) const {
309 return !(pieces(~c, PAWN) & passed_pawn_span(c, s));
312 inline int Position::pawns_on_same_color_squares(Color c, Square s) const {
313 return popcount(pieces(c, PAWN) & ((DarkSquares & s) ? DarkSquares : ~DarkSquares));
316 inline Key Position::key() const {
317 return st->rule50 < 14 ? st->key
318 : st->key ^ make_key((st->rule50 - 14) / 8);
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 non_pawn_material(WHITE) + non_pawn_material(BLACK);
341 inline int Position::game_ply() const {
345 inline int Position::rule50_count() const {
349 inline bool Position::opposite_bishops() const {
350 return count<BISHOP>(WHITE) == 1
351 && count<BISHOP>(BLACK) == 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) == EN_PASSANT;
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] |= byTypeBB[type_of(pc)] |= s;
382 byColorBB[color_of(pc)] |= s;
384 pieceCount[make_piece(color_of(pc), ALL_PIECES)]++;
385 psq += PSQT::psq[pc][s];
388 inline void Position::remove_piece(Square s) {
391 byTypeBB[ALL_PIECES] ^= s;
392 byTypeBB[type_of(pc)] ^= s;
393 byColorBB[color_of(pc)] ^= s;
394 /* board[s] = NO_PIECE; Not needed, overwritten by the capturing one */
396 pieceCount[make_piece(color_of(pc), ALL_PIECES)]--;
397 psq -= PSQT::psq[pc][s];
400 inline void Position::move_piece(Square from, Square to) {
402 Piece pc = board[from];
403 Bitboard fromTo = from | to;
404 byTypeBB[ALL_PIECES] ^= fromTo;
405 byTypeBB[type_of(pc)] ^= fromTo;
406 byColorBB[color_of(pc)] ^= fromTo;
407 board[from] = NO_PIECE;
409 psq += PSQT::psq[pc][to] - PSQT::psq[pc][from];
412 inline void Position::do_move(Move m, StateInfo& newSt) {
413 do_move(m, newSt, gives_check(m));
416 inline StateInfo* Position::state() const {
421 } // namespace Stockfish
423 #endif // #ifndef POSITION_H_INCLUDED