2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2014 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
30 /// The checkInfo struct is initialized at c'tor time and keeps info used
31 /// to detect if a move gives check.
37 explicit CheckInfo(const Position&);
39 Bitboard dcCandidates;
41 Bitboard checkSq[PIECE_TYPE_NB];
46 /// The StateInfo struct stores information needed to restore a Position
47 /// object to its previous state when we retract a move. Whenever a move
48 /// is made on the board (by calling Position::do_move), a StateInfo
49 /// object must be passed as a parameter.
52 Key pawnKey, materialKey;
53 Value npMaterial[COLOR_NB];
54 int castlingRights, rule50, pliesFromNull;
60 PieceType capturedType;
65 /// When making a move the current StateInfo up to 'key' excluded is copied to
66 /// the new one. Here we calculate the quad words (64bits) needed to be copied.
67 const size_t StateCopySize64 = offsetof(StateInfo, key) / sizeof(uint64_t) + 1;
70 /// The Position class stores the information regarding the board representation
71 /// like pieces, side to move, hash keys, castling info, etc. The most important
72 /// methods are do_move() and undo_move(), used by the search to update node info
73 /// when traversing the search tree.
77 friend std::ostream& operator<<(std::ostream&, const Position&);
81 Position(const Position& pos, Thread* t) { *this = pos; thisThread = t; }
82 Position(const std::string& f, bool c960, Thread* t) { set(f, c960, t); }
83 Position& operator=(const Position&);
86 // FEN string input/output
87 void set(const std::string& fenStr, bool isChess960, Thread* th);
88 const std::string fen() const;
90 // Position representation
91 Bitboard pieces() const;
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 king_square(Color c) const;
99 Square ep_square() const;
100 bool empty(Square s) const;
101 template<PieceType Pt> int count(Color c) const;
102 template<PieceType Pt> const Square* list(Color c) const;
105 int can_castle(Color c) const;
106 int can_castle(CastlingRight cr) const;
107 bool castling_impeded(CastlingRight cr) const;
108 Square castling_rook_square(CastlingRight cr) const;
111 Bitboard checkers() const;
112 Bitboard discovered_check_candidates() const;
113 Bitboard pinned_pieces(Color c) const;
115 // Attacks to/from a given square
116 Bitboard attackers_to(Square s) const;
117 Bitboard attackers_to(Square s, Bitboard occ) const;
118 Bitboard attacks_from(Piece pc, Square s) const;
119 template<PieceType> Bitboard attacks_from(Square s) const;
120 template<PieceType> Bitboard attacks_from(Square s, Color c) const;
122 // Properties of moves
123 bool legal(Move m, Bitboard pinned) const;
124 bool pseudo_legal(const Move m) const;
125 bool capture(Move m) const;
126 bool capture_or_promotion(Move m) const;
127 bool gives_check(Move m, const CheckInfo& ci) const;
128 bool advanced_pawn_push(Move m) const;
129 Piece moved_piece(Move m) const;
130 PieceType captured_piece_type() const;
133 bool pawn_passed(Color c, Square s) const;
134 bool pawn_on_7th(Color c) const;
135 bool bishop_pair(Color c) const;
136 bool opposite_bishops() const;
138 // Doing and undoing moves
139 void do_move(Move m, StateInfo& st);
140 void do_move(Move m, StateInfo& st, const CheckInfo& ci, bool moveIsCheck);
141 void undo_move(Move m);
142 void do_null_move(StateInfo& st);
143 void undo_null_move();
145 // Static exchange evaluation
146 Value see(Move m) const;
147 Value see_sign(Move m) const;
149 // Accessing hash keys
151 Key key_after(Move m) const;
152 Key exclusion_key() const;
153 Key pawn_key() const;
154 Key material_key() const;
156 // Incremental piece-square evaluation
157 Score psq_score() const;
158 Value non_pawn_material(Color c) const;
160 // Other properties of the position
161 Color side_to_move() const;
162 Phase game_phase() const;
163 int game_ply() const;
164 bool is_chess960() const;
165 Thread* this_thread() const;
166 uint64_t nodes_searched() const;
167 void set_nodes_searched(uint64_t n);
168 bool is_draw() const;
170 // Position consistency check, for debugging
171 bool pos_is_ok(int* step = NULL) const;
175 // Initialization helpers (used while setting up a position)
177 void set_castling_right(Color c, Square rfrom);
178 void set_state(StateInfo* si) const;
181 Bitboard check_blockers(Color c, Color kingColor) const;
182 void put_piece(Square s, Color c, PieceType pt);
183 void remove_piece(Square s, Color c, PieceType pt);
184 void move_piece(Square from, Square to, Color c, PieceType pt);
186 void do_castling(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[COLOR_NB][PIECE_TYPE_NB];
193 Square pieceList[COLOR_NB][PIECE_TYPE_NB][16];
194 int index[SQUARE_NB];
197 int castlingRightsMask[SQUARE_NB];
198 Square castlingRookSquare[CASTLING_RIGHT_NB];
199 Bitboard castlingPath[CASTLING_RIGHT_NB];
200 StateInfo startState;
209 inline uint64_t Position::nodes_searched() const {
213 inline void Position::set_nodes_searched(uint64_t n) {
217 inline Piece Position::piece_on(Square s) const {
221 inline Piece Position::moved_piece(Move m) const {
222 return board[from_sq(m)];
225 inline bool Position::empty(Square s) const {
226 return board[s] == NO_PIECE;
229 inline Color Position::side_to_move() const {
233 inline Bitboard Position::pieces() const {
234 return byTypeBB[ALL_PIECES];
237 inline Bitboard Position::pieces(PieceType pt) const {
241 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2) const {
242 return byTypeBB[pt1] | byTypeBB[pt2];
245 inline Bitboard Position::pieces(Color c) const {
249 inline Bitboard Position::pieces(Color c, PieceType pt) const {
250 return byColorBB[c] & byTypeBB[pt];
253 inline Bitboard Position::pieces(Color c, PieceType pt1, PieceType pt2) const {
254 return byColorBB[c] & (byTypeBB[pt1] | byTypeBB[pt2]);
257 template<PieceType Pt> inline int Position::count(Color c) const {
258 return pieceCount[c][Pt];
261 template<PieceType Pt> inline const Square* Position::list(Color c) const {
262 return pieceList[c][Pt];
265 inline Square Position::ep_square() const {
269 inline Square Position::king_square(Color c) const {
270 return pieceList[c][KING][0];
273 inline int Position::can_castle(CastlingRight cr) const {
274 return st->castlingRights & cr;
277 inline int Position::can_castle(Color c) const {
278 return st->castlingRights & ((WHITE_OO | WHITE_OOO) << (2 * c));
281 inline bool Position::castling_impeded(CastlingRight cr) const {
282 return byTypeBB[ALL_PIECES] & castlingPath[cr];
285 inline Square Position::castling_rook_square(CastlingRight cr) const {
286 return castlingRookSquare[cr];
289 template<PieceType Pt>
290 inline Bitboard Position::attacks_from(Square s) const {
292 return Pt == BISHOP || Pt == ROOK ? attacks_bb<Pt>(s, byTypeBB[ALL_PIECES])
293 : Pt == QUEEN ? attacks_from<ROOK>(s) | attacks_from<BISHOP>(s)
294 : StepAttacksBB[Pt][s];
298 inline Bitboard Position::attacks_from<PAWN>(Square s, Color c) const {
299 return StepAttacksBB[make_piece(c, PAWN)][s];
302 inline Bitboard Position::attacks_from(Piece pc, Square s) const {
303 return attacks_bb(pc, s, byTypeBB[ALL_PIECES]);
306 inline Bitboard Position::attackers_to(Square s) const {
307 return attackers_to(s, byTypeBB[ALL_PIECES]);
310 inline Bitboard Position::checkers() const {
311 return st->checkersBB;
314 inline Bitboard Position::discovered_check_candidates() const {
315 return check_blockers(sideToMove, ~sideToMove);
318 inline Bitboard Position::pinned_pieces(Color c) const {
319 return check_blockers(c, c);
322 inline bool Position::pawn_passed(Color c, Square s) const {
323 return !(pieces(~c, PAWN) & passed_pawn_mask(c, s));
326 inline bool Position::advanced_pawn_push(Move m) const {
327 return type_of(moved_piece(m)) == PAWN
328 && relative_rank(sideToMove, from_sq(m)) > RANK_4;
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->npMaterial[c];
351 inline int Position::game_ply() const {
355 inline bool Position::opposite_bishops() const {
357 return pieceCount[WHITE][BISHOP] == 1
358 && pieceCount[BLACK][BISHOP] == 1
359 && opposite_colors(pieceList[WHITE][BISHOP][0], pieceList[BLACK][BISHOP][0]);
362 inline bool Position::bishop_pair(Color c) const {
364 return pieceCount[c][BISHOP] >= 2
365 && opposite_colors(pieceList[c][BISHOP][0], pieceList[c][BISHOP][1]);
368 inline bool Position::pawn_on_7th(Color c) const {
369 return pieces(c, PAWN) & rank_bb(relative_rank(c, RANK_7));
372 inline bool Position::is_chess960() const {
376 inline bool Position::capture_or_promotion(Move m) const {
379 return type_of(m) != NORMAL ? type_of(m) != CASTLING : !empty(to_sq(m));
382 inline bool Position::capture(Move m) const {
384 // Note that castling is encoded as "king captures the rook"
386 return (!empty(to_sq(m)) && type_of(m) != CASTLING) || type_of(m) == ENPASSANT;
389 inline PieceType Position::captured_piece_type() const {
390 return st->capturedType;
393 inline Thread* Position::this_thread() const {
397 inline void Position::put_piece(Square s, Color c, PieceType pt) {
399 board[s] = make_piece(c, pt);
400 byTypeBB[ALL_PIECES] |= s;
403 index[s] = pieceCount[c][pt]++;
404 pieceList[c][pt][index[s]] = s;
407 inline void Position::move_piece(Square from, Square to, Color c, PieceType pt) {
409 // index[from] is not updated and becomes stale. This works as long
410 // as index[] is accessed just by known occupied squares.
411 Bitboard from_to_bb = SquareBB[from] ^ SquareBB[to];
412 byTypeBB[ALL_PIECES] ^= from_to_bb;
413 byTypeBB[pt] ^= from_to_bb;
414 byColorBB[c] ^= from_to_bb;
415 board[from] = NO_PIECE;
416 board[to] = make_piece(c, pt);
417 index[to] = index[from];
418 pieceList[c][pt][index[to]] = to;
421 inline void Position::remove_piece(Square s, Color c, PieceType pt) {
423 // WARNING: This is not a reversible operation. If we remove a piece in
424 // do_move() and then replace it in undo_move() we will put it at the end of
425 // the list and not in its original place, it means index[] and pieceList[]
426 // are not guaranteed to be invariant to a do_move() + undo_move() sequence.
427 byTypeBB[ALL_PIECES] ^= s;
430 /* board[s] = NO_PIECE; */ // Not needed, will be overwritten by capturing
431 Square lastSquare = pieceList[c][pt][--pieceCount[c][pt]];
432 index[lastSquare] = index[s];
433 pieceList[c][pt][index[lastSquare]] = lastSquare;
434 pieceList[c][pt][pieceCount[c][pt]] = SQ_NONE;
437 #endif // #ifndef POSITION_H_INCLUDED