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
6 Stockfish is free software: you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation, either version 3 of the License, or
9 (at your option) any later version.
11 Stockfish is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with this program. If not, see <http://www.gnu.org/licenses/>.
20 #ifndef POSITION_H_INCLUDED
21 #define POSITION_H_INCLUDED
24 #include <cstddef> // For offsetof()
35 extern Score psq[COLOR_NB][PIECE_TYPE_NB][SQUARE_NB];
40 /// CheckInfo struct is initialized at constructor time and keeps info used to
41 /// detect if a move gives check.
45 explicit CheckInfo(const Position&);
47 Bitboard dcCandidates;
49 Bitboard checkSquares[PIECE_TYPE_NB];
54 /// StateInfo struct stores information needed to restore a Position object to
55 /// its previous state when we retract a move. Whenever a move is made on the
56 /// board (by calling Position::do_move), a StateInfo object must be passed.
60 // Copied when making a move
63 Value nonPawnMaterial[COLOR_NB];
70 // Not copied when making a move
73 PieceType capturedType;
78 /// Position class stores information regarding the board representation as
79 /// pieces, side to move, hash keys, castling info, etc. Important methods are
80 /// do_move() and undo_move(), used by the search to update node info when
81 /// traversing the search tree.
88 Position() = default; // To define the global object RootPos
89 Position(const Position&) = delete;
90 Position(const Position& pos, Thread* th) { *this = pos; thisThread = th; }
91 Position(const std::string& f, bool c960, Thread* th) { set(f, c960, th); }
92 Position& operator=(const Position&); // To assign RootPos from UCI
94 // FEN string input/output
95 void set(const std::string& fenStr, bool isChess960, Thread* th);
96 const std::string fen() const;
98 // Position representation
99 Bitboard pieces() const;
100 Bitboard pieces(PieceType pt) const;
101 Bitboard pieces(PieceType pt1, PieceType pt2) const;
102 Bitboard pieces(Color c) const;
103 Bitboard pieces(Color c, PieceType pt) const;
104 Bitboard pieces(Color c, PieceType pt1, PieceType pt2) const;
105 Piece piece_on(Square s) const;
106 Square ep_square() const;
107 bool empty(Square s) const;
108 template<PieceType Pt> int count(Color c) const;
109 template<PieceType Pt> const Square* squares(Color c) const;
110 template<PieceType Pt> Square square(Color c) const;
113 int can_castle(Color c) const;
114 int can_castle(CastlingRight cr) const;
115 bool castling_impeded(CastlingRight cr) const;
116 Square castling_rook_square(CastlingRight cr) const;
119 Bitboard checkers() const;
120 Bitboard discovered_check_candidates() const;
121 Bitboard pinned_pieces(Color c) const;
123 // Attacks to/from a given square
124 Bitboard attackers_to(Square s) const;
125 Bitboard attackers_to(Square s, Bitboard occupied) const;
126 Bitboard attacks_from(Piece pc, Square s) const;
127 template<PieceType> Bitboard attacks_from(Square s) const;
128 template<PieceType> Bitboard attacks_from(Square s, Color c) const;
130 // Properties of moves
131 bool legal(Move m, Bitboard pinned) const;
132 bool pseudo_legal(const Move m) const;
133 bool capture(Move m) const;
134 bool capture_or_promotion(Move m) const;
135 bool gives_check(Move m, const CheckInfo& ci) const;
136 bool advanced_pawn_push(Move m) const;
137 Piece moved_piece(Move m) const;
138 PieceType captured_piece_type() const;
141 bool pawn_passed(Color c, Square s) const;
142 bool opposite_bishops() const;
144 // Doing and undoing moves
145 void do_move(Move m, StateInfo& st, bool givesCheck);
146 void undo_move(Move m);
147 void do_null_move(StateInfo& st);
148 void undo_null_move();
150 // Static exchange evaluation
151 Value see(Move m) const;
152 Value see_sign(Move m) const;
154 // Accessing hash keys
156 Key key_after(Move m) const;
157 Key exclusion_key() const;
158 Key material_key() const;
159 Key pawn_key() const;
161 // Other properties of the position
162 Color side_to_move() const;
163 Phase game_phase() const;
164 int game_ply() const;
165 bool is_chess960() const;
166 Thread* this_thread() const;
167 uint64_t nodes_searched() const;
168 void set_nodes_searched(uint64_t n);
169 bool is_draw() const;
170 int rule50_count() const;
171 Score psq_score() const;
172 Value non_pawn_material(Color c) const;
174 // Position consistency check, for debugging
175 bool pos_is_ok(int* failedStep = nullptr) const;
179 // Initialization helpers (used while setting up a position)
181 void set_castling_right(Color c, Square rfrom);
182 void set_state(StateInfo* si) const;
185 Bitboard check_blockers(Color c, Color kingColor) const;
186 void put_piece(Color c, PieceType pt, Square s);
187 void remove_piece(Color c, PieceType pt, Square s);
188 void move_piece(Color c, PieceType pt, Square from, Square to);
190 void do_castling(Color us, Square from, Square& to, Square& rfrom, Square& rto);
193 Piece board[SQUARE_NB];
194 Bitboard byTypeBB[PIECE_TYPE_NB];
195 Bitboard byColorBB[COLOR_NB];
196 int pieceCount[COLOR_NB][PIECE_TYPE_NB];
197 Square pieceList[COLOR_NB][PIECE_TYPE_NB][16];
198 int index[SQUARE_NB];
199 int castlingRightsMask[SQUARE_NB];
200 Square castlingRookSquare[CASTLING_RIGHT_NB];
201 Bitboard castlingPath[CASTLING_RIGHT_NB];
202 StateInfo startState;
211 extern std::ostream& operator<<(std::ostream& os, const Position& pos);
213 inline Color Position::side_to_move() const {
217 inline bool Position::empty(Square s) const {
218 return board[s] == NO_PIECE;
221 inline Piece Position::piece_on(Square s) const {
225 inline Piece Position::moved_piece(Move m) const {
226 return board[from_sq(m)];
229 inline Bitboard Position::pieces() const {
230 return byTypeBB[ALL_PIECES];
233 inline Bitboard Position::pieces(PieceType pt) const {
237 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2) const {
238 return byTypeBB[pt1] | byTypeBB[pt2];
241 inline Bitboard Position::pieces(Color c) const {
245 inline Bitboard Position::pieces(Color c, PieceType pt) const {
246 return byColorBB[c] & byTypeBB[pt];
249 inline Bitboard Position::pieces(Color c, PieceType pt1, PieceType pt2) const {
250 return byColorBB[c] & (byTypeBB[pt1] | byTypeBB[pt2]);
253 template<PieceType Pt> inline int Position::count(Color c) const {
254 return pieceCount[c][Pt];
257 template<PieceType Pt> inline const Square* Position::squares(Color c) const {
258 return pieceList[c][Pt];
261 template<PieceType Pt> inline Square Position::square(Color c) const {
262 assert(pieceCount[c][Pt] == 1);
263 return pieceList[c][Pt][0];
266 inline Square Position::ep_square() const {
270 inline int Position::can_castle(CastlingRight cr) const {
271 return st->castlingRights & cr;
274 inline int Position::can_castle(Color c) const {
275 return st->castlingRights & ((WHITE_OO | WHITE_OOO) << (2 * c));
278 inline bool Position::castling_impeded(CastlingRight cr) const {
279 return byTypeBB[ALL_PIECES] & castlingPath[cr];
282 inline Square Position::castling_rook_square(CastlingRight cr) const {
283 return castlingRookSquare[cr];
286 template<PieceType Pt>
287 inline Bitboard Position::attacks_from(Square s) const {
288 return Pt == BISHOP || Pt == ROOK ? attacks_bb<Pt>(s, byTypeBB[ALL_PIECES])
289 : Pt == QUEEN ? attacks_from<ROOK>(s) | attacks_from<BISHOP>(s)
290 : StepAttacksBB[Pt][s];
294 inline Bitboard Position::attacks_from<PAWN>(Square s, Color c) const {
295 return StepAttacksBB[make_piece(c, PAWN)][s];
298 inline Bitboard Position::attacks_from(Piece pc, Square s) const {
299 return attacks_bb(pc, s, byTypeBB[ALL_PIECES]);
302 inline Bitboard Position::attackers_to(Square s) const {
303 return attackers_to(s, byTypeBB[ALL_PIECES]);
306 inline Bitboard Position::checkers() const {
307 return st->checkersBB;
310 inline Bitboard Position::discovered_check_candidates() const {
311 return check_blockers(sideToMove, ~sideToMove);
314 inline Bitboard Position::pinned_pieces(Color c) const {
315 return check_blockers(c, c);
318 inline bool Position::pawn_passed(Color c, Square s) const {
319 return !(pieces(~c, PAWN) & passed_pawn_mask(c, s));
322 inline bool Position::advanced_pawn_push(Move m) const {
323 return type_of(moved_piece(m)) == PAWN
324 && relative_rank(sideToMove, from_sq(m)) > RANK_4;
327 inline Key Position::key() const {
331 inline Key Position::pawn_key() const {
335 inline Key Position::material_key() const {
336 return st->materialKey;
339 inline Score Position::psq_score() const {
343 inline Value Position::non_pawn_material(Color c) const {
344 return st->nonPawnMaterial[c];
347 inline int Position::game_ply() const {
351 inline int Position::rule50_count() const {
355 inline uint64_t Position::nodes_searched() const {
359 inline void Position::set_nodes_searched(uint64_t n) {
363 inline bool Position::opposite_bishops() const {
364 return pieceCount[WHITE][BISHOP] == 1
365 && pieceCount[BLACK][BISHOP] == 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 {
376 return type_of(m) != NORMAL ? type_of(m) != CASTLING : !empty(to_sq(m));
379 inline bool Position::capture(Move m) const {
381 // Castling is encoded as "king captures the rook"
383 return (!empty(to_sq(m)) && type_of(m) != CASTLING) || type_of(m) == ENPASSANT;
386 inline PieceType Position::captured_piece_type() const {
387 return st->capturedType;
390 inline Thread* Position::this_thread() const {
394 inline void Position::put_piece(Color c, PieceType pt, Square s) {
396 board[s] = make_piece(c, pt);
397 byTypeBB[ALL_PIECES] |= s;
400 index[s] = pieceCount[c][pt]++;
401 pieceList[c][pt][index[s]] = s;
402 pieceCount[c][ALL_PIECES]++;
405 inline void Position::remove_piece(Color c, PieceType pt, Square s) {
407 // WARNING: This is not a reversible operation. If we remove a piece in
408 // do_move() and then replace it in undo_move() we will put it at the end of
409 // the list and not in its original place, it means index[] and pieceList[]
410 // are not guaranteed to be invariant to a do_move() + undo_move() sequence.
411 byTypeBB[ALL_PIECES] ^= s;
414 /* board[s] = NO_PIECE; Not needed, overwritten by the capturing one */
415 Square lastSquare = pieceList[c][pt][--pieceCount[c][pt]];
416 index[lastSquare] = index[s];
417 pieceList[c][pt][index[lastSquare]] = lastSquare;
418 pieceList[c][pt][pieceCount[c][pt]] = SQ_NONE;
419 pieceCount[c][ALL_PIECES]--;
422 inline void Position::move_piece(Color c, PieceType pt, 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 Bitboard from_to_bb = SquareBB[from] ^ SquareBB[to];
427 byTypeBB[ALL_PIECES] ^= from_to_bb;
428 byTypeBB[pt] ^= from_to_bb;
429 byColorBB[c] ^= from_to_bb;
430 board[from] = NO_PIECE;
431 board[to] = make_piece(c, pt);
432 index[to] = index[from];
433 pieceList[c][pt][index[to]] = to;
436 #endif // #ifndef POSITION_H_INCLUDED