2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2020 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
31 #include "nnue/nnue_accumulator.h"
34 /// StateInfo struct stores information needed to restore a Position object to
35 /// its previous state when we retract a move. Whenever a move is made on the
36 /// board (by calling Position::do_move), a StateInfo object must be passed.
40 // Copied when making a move
43 Value nonPawnMaterial[COLOR_NB];
49 // Not copied when making a move (will be recomputed anyhow)
54 Bitboard blockersForKing[COLOR_NB];
55 Bitboard pinners[COLOR_NB];
56 Bitboard checkSquares[PIECE_TYPE_NB];
60 Eval::NNUE::Accumulator accumulator;
61 DirtyPiece dirtyPiece;
65 /// A list to keep track of the position states along the setup moves (from the
66 /// start position to the position just before the search starts). Needed by
67 /// 'draw by repetition' detection. Use a std::deque because pointers to
68 /// elements are not invalidated upon list resizing.
69 typedef std::unique_ptr<std::deque<StateInfo>> StateListPtr;
72 /// Position class stores information regarding the board representation as
73 /// pieces, side to move, hash keys, castling info, etc. Important methods are
74 /// do_move() and undo_move(), used by the search to update node info when
75 /// traversing the search tree.
83 Position(const Position&) = delete;
84 Position& operator=(const Position&) = delete;
86 // FEN string input/output
87 Position& set(const std::string& fenStr, bool isChess960, StateInfo* si, Thread* th);
88 Position& set(const std::string& code, Color c, StateInfo* si);
89 const std::string fen() const;
91 // Position representation
92 Bitboard pieces(PieceType pt) const;
93 Bitboard pieces(PieceType pt1, PieceType pt2) const;
94 Bitboard pieces(Color c) const;
95 Bitboard pieces(Color c, PieceType pt) const;
96 Bitboard pieces(Color c, PieceType pt1, PieceType pt2) const;
97 Piece piece_on(Square s) const;
98 Square ep_square() const;
99 bool empty(Square s) const;
100 template<PieceType Pt> int count(Color c) const;
101 template<PieceType Pt> int count() const;
102 template<PieceType Pt> const Square* squares(Color c) const;
103 template<PieceType Pt> Square square(Color c) const;
104 bool is_on_semiopen_file(Color c, Square s) const;
107 CastlingRights castling_rights(Color c) const;
108 bool can_castle(CastlingRights cr) const;
109 bool castling_impeded(CastlingRights cr) const;
110 Square castling_rook_square(CastlingRights cr) const;
113 Bitboard checkers() const;
114 Bitboard blockers_for_king(Color c) const;
115 Bitboard check_squares(PieceType pt) const;
116 Bitboard pinners(Color c) const;
117 bool is_discovery_check_on_king(Color c, Move m) const;
119 // Attacks to/from a given square
120 Bitboard attackers_to(Square s) const;
121 Bitboard attackers_to(Square s, Bitboard occupied) const;
122 Bitboard slider_blockers(Bitboard sliders, Square s, Bitboard& pinners) const;
124 // Properties of moves
125 bool legal(Move m) const;
126 bool pseudo_legal(const Move m) const;
127 bool capture(Move m) const;
128 bool capture_or_promotion(Move m) const;
129 bool gives_check(Move m) const;
130 bool advanced_pawn_push(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 Square pieceList[PIECE_NB][16];
194 int index[SQUARE_NB];
195 int castlingRightsMask[SQUARE_NB];
196 Square castlingRookSquare[CASTLING_RIGHT_NB];
197 Bitboard castlingPath[CASTLING_RIGHT_NB];
207 extern Score psq[PIECE_NB][SQUARE_NB];
210 extern std::ostream& operator<<(std::ostream& os, const Position& pos);
212 inline Color Position::side_to_move() const {
216 inline Piece Position::piece_on(Square s) const {
221 inline bool Position::empty(Square s) const {
222 return piece_on(s) == NO_PIECE;
225 inline Piece Position::moved_piece(Move m) const {
226 return piece_on(from_sq(m));
229 inline Bitboard Position::pieces(PieceType pt = ALL_PIECES) const {
233 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2) const {
234 return pieces(pt1) | pieces(pt2);
237 inline Bitboard Position::pieces(Color c) const {
241 inline Bitboard Position::pieces(Color c, PieceType pt) const {
242 return pieces(c) & pieces(pt);
245 inline Bitboard Position::pieces(Color c, PieceType pt1, PieceType pt2) const {
246 return pieces(c) & (pieces(pt1) | pieces(pt2));
249 template<PieceType Pt> inline int Position::count(Color c) const {
250 return pieceCount[make_piece(c, Pt)];
253 template<PieceType Pt> inline int Position::count() const {
254 return count<Pt>(WHITE) + count<Pt>(BLACK);
257 template<PieceType Pt> inline const Square* Position::squares(Color c) const {
258 return pieceList[make_piece(c, Pt)];
261 template<PieceType Pt> inline Square Position::square(Color c) const {
262 assert(pieceCount[make_piece(c, Pt)] == 1);
263 return squares<Pt>(c)[0];
266 inline Square Position::ep_square() const {
270 inline bool Position::is_on_semiopen_file(Color c, Square s) const {
271 return !(pieces(c, PAWN) & file_bb(s));
274 inline bool Position::can_castle(CastlingRights cr) const {
275 return st->castlingRights & cr;
278 inline CastlingRights Position::castling_rights(Color c) const {
279 return c & CastlingRights(st->castlingRights);
282 inline bool Position::castling_impeded(CastlingRights cr) const {
283 assert(cr == WHITE_OO || cr == WHITE_OOO || cr == BLACK_OO || cr == BLACK_OOO);
285 return pieces() & castlingPath[cr];
288 inline Square Position::castling_rook_square(CastlingRights cr) const {
289 assert(cr == WHITE_OO || cr == WHITE_OOO || cr == BLACK_OO || cr == BLACK_OOO);
291 return castlingRookSquare[cr];
294 inline Bitboard Position::attackers_to(Square s) const {
295 return attackers_to(s, pieces());
298 inline Bitboard Position::checkers() const {
299 return st->checkersBB;
302 inline Bitboard Position::blockers_for_king(Color c) const {
303 return st->blockersForKing[c];
306 inline Bitboard Position::pinners(Color c) const {
307 return st->pinners[c];
310 inline Bitboard Position::check_squares(PieceType pt) const {
311 return st->checkSquares[pt];
314 inline bool Position::is_discovery_check_on_king(Color c, Move m) const {
315 return st->blockersForKing[c] & from_sq(m);
318 inline bool Position::pawn_passed(Color c, Square s) const {
319 return !(pieces(~c, PAWN) & passed_pawn_span(c, s));
322 inline bool Position::advanced_pawn_push(Move m) const {
323 return type_of(moved_piece(m)) == PAWN
324 && relative_rank(sideToMove, to_sq(m)) > RANK_5;
327 inline int Position::pawns_on_same_color_squares(Color c, Square s) const {
328 return popcount(pieces(c, PAWN) & ((DarkSquares & s) ? DarkSquares : ~DarkSquares));
331 inline Key Position::key() const {
335 inline Key Position::pawn_key() const {
339 inline Key Position::material_key() const {
340 return st->materialKey;
343 inline Score Position::psq_score() const {
347 inline Value Position::non_pawn_material(Color c) const {
348 return st->nonPawnMaterial[c];
351 inline Value Position::non_pawn_material() const {
352 return non_pawn_material(WHITE) + non_pawn_material(BLACK);
355 inline int Position::game_ply() const {
359 inline int Position::rule50_count() const {
363 inline bool Position::opposite_bishops() const {
364 return count<BISHOP>(WHITE) == 1
365 && count<BISHOP>(BLACK) == 1
366 && opposite_colors(square<BISHOP>(WHITE), square<BISHOP>(BLACK));
369 inline bool Position::is_chess960() const {
373 inline bool Position::capture_or_promotion(Move m) const {
375 return type_of(m) != NORMAL ? type_of(m) != CASTLING : !empty(to_sq(m));
378 inline bool Position::capture(Move m) const {
380 // Castling is encoded as "king captures rook"
381 return (!empty(to_sq(m)) && type_of(m) != CASTLING) || type_of(m) == ENPASSANT;
384 inline Piece Position::captured_piece() const {
385 return st->capturedPiece;
388 inline Thread* Position::this_thread() const {
392 inline void Position::put_piece(Piece pc, Square s) {
395 byTypeBB[ALL_PIECES] |= 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)]++;
400 psq += PSQT::psq[pc][s];
403 inline void Position::remove_piece(Square s) {
405 // WARNING: This is not a reversible operation. If we remove a piece in
406 // do_move() and then replace it in undo_move() we will put it at the end of
407 // the list and not in its original place, it means index[] and pieceList[]
408 // are not invariant to a do_move() + undo_move() sequence.
410 byTypeBB[ALL_PIECES] ^= s;
411 byTypeBB[type_of(pc)] ^= s;
412 byColorBB[color_of(pc)] ^= s;
413 /* board[s] = NO_PIECE; Not needed, overwritten by the capturing one */
414 Square lastSquare = pieceList[pc][--pieceCount[pc]];
415 index[lastSquare] = index[s];
416 pieceList[pc][index[lastSquare]] = lastSquare;
417 pieceList[pc][pieceCount[pc]] = SQ_NONE;
418 pieceCount[make_piece(color_of(pc), ALL_PIECES)]--;
419 psq -= PSQT::psq[pc][s];
422 inline void Position::move_piece(Square from, Square to) {
424 // index[from] is not updated and becomes stale. This works as long as index[]
425 // is accessed just by known occupied squares.
426 Piece pc = board[from];
427 Bitboard fromTo = from | to;
428 byTypeBB[ALL_PIECES] ^= fromTo;
429 byTypeBB[type_of(pc)] ^= fromTo;
430 byColorBB[color_of(pc)] ^= fromTo;
431 board[from] = NO_PIECE;
433 index[to] = index[from];
434 pieceList[pc][index[to]] = to;
435 psq += PSQT::psq[pc][to] - PSQT::psq[pc][from];
438 inline void Position::do_move(Move m, StateInfo& newSt) {
439 do_move(m, newSt, gives_check(m));
442 inline StateInfo* Position::state() const {
447 #endif // #ifndef POSITION_H_INCLUDED