2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2013 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 we need 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 object
49 /// must be passed as a parameter.
52 Key pawnKey, materialKey;
53 Value npMaterial[COLOR_NB];
54 int castleRights, 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 data structure. A position consists of the following data:
72 /// * For each piece type, a bitboard representing the squares occupied
73 /// by pieces of that type.
74 /// * For each color, a bitboard representing the squares occupied by
75 /// pieces of that color.
76 /// * A bitboard of all occupied squares.
77 /// * A bitboard of all checking pieces.
78 /// * A 64-entry array of pieces, indexed by the squares of the board.
79 /// * The current side to move.
80 /// * Information about the castling rights for both sides.
81 /// * The initial files of the kings and both pairs of rooks. This is
82 /// used to implement the Chess960 castling rules.
83 /// * The en passant square (which is SQ_NONE if no en passant capture is
85 /// * The squares of the kings for both sides.
86 /// * Hash keys for the position itself, the current pawn structure, and
87 /// the current material situation.
88 /// * Hash keys for all previous positions in the game for detecting
90 /// * A counter for detecting 50 move rule draws.
95 Position(const Position& p, Thread* t) { *this = p; thisThread = t; }
96 Position(const std::string& f, bool c960, Thread* t) { set(f, c960, t); }
97 Position& operator=(const Position&);
101 void set(const std::string& fen, bool isChess960, Thread* th);
102 const std::string fen() const;
103 const std::string pretty(Move m = MOVE_NONE) const;
105 // Position representation
106 Bitboard pieces() const;
107 Bitboard pieces(PieceType pt) const;
108 Bitboard pieces(PieceType pt1, PieceType pt2) const;
109 Bitboard pieces(Color c) const;
110 Bitboard pieces(Color c, PieceType pt) const;
111 Bitboard pieces(Color c, PieceType pt1, PieceType pt2) const;
112 Piece piece_on(Square s) const;
113 Square king_square(Color c) const;
114 Square ep_square() const;
115 bool is_empty(Square s) const;
116 template<PieceType Pt> int count(Color c) const;
117 template<PieceType Pt> const Square* list(Color c) const;
120 int can_castle(CastleRight f) const;
121 int can_castle(Color c) const;
122 bool castle_impeded(Color c, CastlingSide s) const;
123 Square castle_rook_square(Color c, CastlingSide s) const;
126 Bitboard checkers() const;
127 Bitboard discovered_check_candidates() const;
128 Bitboard pinned_pieces() const;
130 // Attacks to/from a given square
131 Bitboard attackers_to(Square s) const;
132 Bitboard attackers_to(Square s, Bitboard occ) const;
133 Bitboard attacks_from(Piece p, Square s) const;
134 static Bitboard attacks_from(Piece p, Square s, Bitboard occ);
135 template<PieceType> Bitboard attacks_from(Square s) const;
136 template<PieceType> Bitboard attacks_from(Square s, Color c) const;
138 // Properties of moves
139 bool move_gives_check(Move m, const CheckInfo& ci) const;
140 bool pl_move_is_legal(Move m, Bitboard pinned) const;
141 bool is_pseudo_legal(const Move m) const;
142 bool is_capture(Move m) const;
143 bool is_capture_or_promotion(Move m) const;
144 bool is_passed_pawn_push(Move m) const;
145 Piece piece_moved(Move m) const;
146 PieceType captured_piece_type() const;
149 bool pawn_is_passed(Color c, Square s) const;
150 bool pawn_on_7th(Color c) const;
151 bool opposite_bishops() const;
152 bool bishop_pair(Color c) const;
154 // Doing and undoing moves
155 void do_move(Move m, StateInfo& st);
156 void do_move(Move m, StateInfo& st, const CheckInfo& ci, bool moveIsCheck);
157 void undo_move(Move m);
158 void do_null_move(StateInfo& st);
159 void undo_null_move();
161 // Static exchange evaluation
162 int see(Move m, int asymmThreshold = 0) const;
163 int see_sign(Move m) const;
165 // Accessing hash keys
167 Key exclusion_key() const;
168 Key pawn_key() const;
169 Key material_key() const;
171 // Incremental piece-square evaluation
172 Score psq_score() const;
173 Value non_pawn_material(Color c) const;
175 // Other properties of the position
176 Color side_to_move() const;
177 int game_ply() const;
178 bool is_chess960() const;
179 Thread* this_thread() const;
180 int64_t nodes_searched() const;
181 void set_nodes_searched(int64_t n);
182 bool is_draw() const;
184 // Position consistency check, for debugging
185 bool pos_is_ok(int* failedStep = NULL) const;
189 // Initialization helpers (used while setting up a position)
191 void put_piece(Piece p, Square s);
192 void set_castle_right(Color c, Square rfrom);
195 void do_castle(Square kfrom, Square kto, Square rfrom, Square rto);
196 Bitboard hidden_checkers(Square ksq, Color c) const;
197 void remove_piece(Square s, Color c, PieceType pt);
198 void add_piece(Square s, Color c, PieceType pt);
199 void move_piece(Square from, Square to, Color c, PieceType pt);
201 // Computing hash keys from scratch (for initialization and debugging)
202 Key compute_key() const;
203 Key compute_pawn_key() const;
204 Key compute_material_key() const;
206 // Computing incremental evaluation scores and material counts
207 Score compute_psq_score() const;
208 Value compute_non_pawn_material(Color c) const;
211 Piece board[SQUARE_NB];
212 Bitboard byTypeBB[PIECE_TYPE_NB];
213 Bitboard byColorBB[COLOR_NB];
214 int pieceCount[COLOR_NB][PIECE_TYPE_NB];
215 Square pieceList[COLOR_NB][PIECE_TYPE_NB][16];
216 int index[SQUARE_NB];
219 int castleRightsMask[SQUARE_NB];
220 Square castleRookSquare[COLOR_NB][CASTLING_SIDE_NB];
221 Bitboard castlePath[COLOR_NB][CASTLING_SIDE_NB];
222 StateInfo startState;
231 inline int64_t Position::nodes_searched() const {
235 inline void Position::set_nodes_searched(int64_t n) {
239 inline Piece Position::piece_on(Square s) const {
243 inline Piece Position::piece_moved(Move m) const {
244 return board[from_sq(m)];
247 inline bool Position::is_empty(Square s) const {
248 return board[s] == NO_PIECE;
251 inline Color Position::side_to_move() const {
255 inline Bitboard Position::pieces() const {
256 return byTypeBB[ALL_PIECES];
259 inline Bitboard Position::pieces(PieceType pt) const {
263 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2) const {
264 return byTypeBB[pt1] | byTypeBB[pt2];
267 inline Bitboard Position::pieces(Color c) const {
271 inline Bitboard Position::pieces(Color c, PieceType pt) const {
272 return byColorBB[c] & byTypeBB[pt];
275 inline Bitboard Position::pieces(Color c, PieceType pt1, PieceType pt2) const {
276 return byColorBB[c] & (byTypeBB[pt1] | byTypeBB[pt2]);
279 template<PieceType Pt> inline int Position::count(Color c) const {
280 return pieceCount[c][Pt];
283 template<PieceType Pt> inline const Square* Position::list(Color c) const {
284 return pieceList[c][Pt];
287 inline Square Position::ep_square() const {
291 inline Square Position::king_square(Color c) const {
292 return pieceList[c][KING][0];
295 inline int Position::can_castle(CastleRight f) const {
296 return st->castleRights & f;
299 inline int Position::can_castle(Color c) const {
300 return st->castleRights & ((WHITE_OO | WHITE_OOO) << (2 * c));
303 inline bool Position::castle_impeded(Color c, CastlingSide s) const {
304 return byTypeBB[ALL_PIECES] & castlePath[c][s];
307 inline Square Position::castle_rook_square(Color c, CastlingSide s) const {
308 return castleRookSquare[c][s];
311 template<PieceType Pt>
312 inline Bitboard Position::attacks_from(Square s) const {
314 return Pt == BISHOP || Pt == ROOK ? attacks_bb<Pt>(s, pieces())
315 : Pt == QUEEN ? attacks_from<ROOK>(s) | attacks_from<BISHOP>(s)
316 : StepAttacksBB[Pt][s];
320 inline Bitboard Position::attacks_from<PAWN>(Square s, Color c) const {
321 return StepAttacksBB[make_piece(c, PAWN)][s];
324 inline Bitboard Position::attacks_from(Piece p, Square s) const {
325 return attacks_from(p, s, byTypeBB[ALL_PIECES]);
328 inline Bitboard Position::attackers_to(Square s) const {
329 return attackers_to(s, byTypeBB[ALL_PIECES]);
332 inline Bitboard Position::checkers() const {
333 return st->checkersBB;
336 inline Bitboard Position::discovered_check_candidates() const {
337 return hidden_checkers(king_square(~sideToMove), sideToMove);
340 inline Bitboard Position::pinned_pieces() const {
341 return hidden_checkers(king_square(sideToMove), ~sideToMove);
344 inline bool Position::pawn_is_passed(Color c, Square s) const {
345 return !(pieces(~c, PAWN) & passed_pawn_mask(c, s));
348 inline Key Position::key() const {
352 inline Key Position::pawn_key() const {
356 inline Key Position::material_key() const {
357 return st->materialKey;
360 inline Score Position::psq_score() const {
364 inline Value Position::non_pawn_material(Color c) const {
365 return st->npMaterial[c];
368 inline bool Position::is_passed_pawn_push(Move m) const {
370 return type_of(piece_moved(m)) == PAWN
371 && pawn_is_passed(sideToMove, to_sq(m));
374 inline int Position::game_ply() const {
378 inline bool Position::opposite_bishops() const {
380 return pieceCount[WHITE][BISHOP] == 1
381 && pieceCount[BLACK][BISHOP] == 1
382 && opposite_colors(pieceList[WHITE][BISHOP][0], pieceList[BLACK][BISHOP][0]);
385 inline bool Position::bishop_pair(Color c) const {
387 return pieceCount[c][BISHOP] >= 2
388 && opposite_colors(pieceList[c][BISHOP][0], pieceList[c][BISHOP][1]);
391 inline bool Position::pawn_on_7th(Color c) const {
392 return pieces(c, PAWN) & rank_bb(relative_rank(c, RANK_7));
395 inline bool Position::is_chess960() const {
399 inline bool Position::is_capture_or_promotion(Move m) const {
402 return type_of(m) ? type_of(m) != CASTLE : !is_empty(to_sq(m));
405 inline bool Position::is_capture(Move m) const {
407 // Note that castle is coded as "king captures the rook"
409 return (!is_empty(to_sq(m)) && type_of(m) != CASTLE) || type_of(m) == ENPASSANT;
412 inline PieceType Position::captured_piece_type() const {
413 return st->capturedType;
416 inline Thread* Position::this_thread() const {
420 inline void Position::add_piece(Square s, Color c, PieceType pt) {
421 index[s] = pieceCount[c][pt]++;
422 pieceList[c][pt][index[s]] = s;
425 inline void Position::move_piece(Square from, Square to, Color c, PieceType pt) {
426 // index[from] is not updated and becomes stale. This works as long
427 // as index[] is accessed just by known occupied squares.
428 index[to] = index[from];
429 pieceList[c][pt][index[to]] = to;
432 inline void Position::remove_piece(Square s, Color c, PieceType pt) {
433 // WARNING: This is not a reversible operation. If we remove a piece in
434 // do_move() and then replace it in undo_move() we will put it at the end of
435 // the list and not in its original place, it means index[] and pieceList[]
436 // are not guaranteed to be invariant to a do_move() + undo_move() sequence.
437 Square lastSquare = pieceList[c][pt][--pieceCount[c][pt]];
438 index[lastSquare] = index[s];
439 pieceList[c][pt][index[lastSquare]] = lastSquare;
440 pieceList[c][pt][pieceCount[c][pt]] = SQ_NONE;
443 #endif // #ifndef POSITION_H_INCLUDED