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 #if !defined(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&);
100 void set(const std::string& fen, bool isChess960, Thread* th);
101 const std::string fen() const;
102 const std::string pretty(Move m = MOVE_NONE) const;
104 // Position representation
105 Bitboard pieces() const;
106 Bitboard pieces(PieceType pt) const;
107 Bitboard pieces(PieceType pt1, PieceType pt2) const;
108 Bitboard pieces(Color c) const;
109 Bitboard pieces(Color c, PieceType pt) const;
110 Bitboard pieces(Color c, PieceType pt1, PieceType pt2) const;
111 Piece piece_on(Square s) const;
112 Square king_square(Color c) const;
113 Square ep_square() const;
114 bool is_empty(Square s) const;
115 const Square* piece_list(Color c, PieceType pt) const;
116 int piece_count(Color c, PieceType pt) const;
119 int can_castle(CastleRight f) const;
120 int can_castle(Color c) const;
121 bool castle_impeded(Color c, CastlingSide s) const;
122 Square castle_rook_square(Color c, CastlingSide s) const;
125 Bitboard checkers() const;
126 Bitboard discovered_check_candidates() const;
127 Bitboard pinned_pieces() const;
129 // Attacks to/from a given square
130 Bitboard attackers_to(Square s) const;
131 Bitboard attackers_to(Square s, Bitboard occ) const;
132 Bitboard attacks_from(Piece p, Square s) const;
133 static Bitboard attacks_from(Piece p, Square s, Bitboard occ);
134 template<PieceType> Bitboard attacks_from(Square s) const;
135 template<PieceType> Bitboard attacks_from(Square s, Color c) const;
137 // Properties of moves
138 bool move_gives_check(Move m, const CheckInfo& ci) const;
139 bool pl_move_is_legal(Move m, Bitboard pinned) const;
140 bool is_pseudo_legal(const Move m) const;
141 bool is_capture(Move m) const;
142 bool is_capture_or_promotion(Move m) const;
143 bool is_passed_pawn_push(Move m) const;
144 Piece piece_moved(Move m) const;
145 PieceType captured_piece_type() const;
148 bool pawn_is_passed(Color c, Square s) const;
149 bool pawn_on_7th(Color c) const;
150 bool opposite_bishops() const;
151 bool bishop_pair(Color c) const;
153 // Doing and undoing moves
154 void do_move(Move m, StateInfo& st);
155 void do_move(Move m, StateInfo& st, const CheckInfo& ci, bool moveIsCheck);
156 void undo_move(Move m);
157 void do_null_move(StateInfo& st);
158 void undo_null_move();
160 // Static exchange evaluation
161 int see(Move m, int asymmThreshold = 0) const;
162 int see_sign(Move m) const;
164 // Accessing hash keys
166 Key exclusion_key() const;
167 Key pawn_key() const;
168 Key material_key() const;
170 // Incremental piece-square evaluation
171 Score psq_score() const;
172 Score psq_delta(Piece p, Square from, Square to) 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 template<bool FindPinned> Bitboard hidden_checkers() const;
198 // Computing hash keys from scratch (for initialization and debugging)
199 Key compute_key() const;
200 Key compute_pawn_key() const;
201 Key compute_material_key() const;
203 // Computing incremental evaluation scores and material counts
204 Score compute_psq_score() const;
205 Value compute_non_pawn_material(Color c) const;
208 Piece board[SQUARE_NB];
209 Bitboard byTypeBB[PIECE_TYPE_NB];
210 Bitboard byColorBB[COLOR_NB];
211 int pieceCount[COLOR_NB][PIECE_TYPE_NB];
212 Square pieceList[COLOR_NB][PIECE_TYPE_NB][16];
213 int index[SQUARE_NB];
216 int castleRightsMask[SQUARE_NB];
217 Square castleRookSquare[COLOR_NB][CASTLING_SIDE_NB];
218 Bitboard castlePath[COLOR_NB][CASTLING_SIDE_NB];
219 StateInfo startState;
228 inline int64_t Position::nodes_searched() const {
232 inline void Position::set_nodes_searched(int64_t n) {
236 inline Piece Position::piece_on(Square s) const {
240 inline Piece Position::piece_moved(Move m) const {
241 return board[from_sq(m)];
244 inline bool Position::is_empty(Square s) const {
245 return board[s] == NO_PIECE;
248 inline Color Position::side_to_move() const {
252 inline Bitboard Position::pieces() const {
253 return byTypeBB[ALL_PIECES];
256 inline Bitboard Position::pieces(PieceType pt) const {
260 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2) const {
261 return byTypeBB[pt1] | byTypeBB[pt2];
264 inline Bitboard Position::pieces(Color c) const {
268 inline Bitboard Position::pieces(Color c, PieceType pt) const {
269 return byColorBB[c] & byTypeBB[pt];
272 inline Bitboard Position::pieces(Color c, PieceType pt1, PieceType pt2) const {
273 return byColorBB[c] & (byTypeBB[pt1] | byTypeBB[pt2]);
276 inline int Position::piece_count(Color c, PieceType pt) const {
277 return pieceCount[c][pt];
280 inline const Square* Position::piece_list(Color c, PieceType pt) const {
281 return pieceList[c][pt];
284 inline Square Position::ep_square() const {
288 inline Square Position::king_square(Color c) const {
289 return pieceList[c][KING][0];
292 inline int Position::can_castle(CastleRight f) const {
293 return st->castleRights & f;
296 inline int Position::can_castle(Color c) const {
297 return st->castleRights & ((WHITE_OO | WHITE_OOO) << (2 * c));
300 inline bool Position::castle_impeded(Color c, CastlingSide s) const {
301 return byTypeBB[ALL_PIECES] & castlePath[c][s];
304 inline Square Position::castle_rook_square(Color c, CastlingSide s) const {
305 return castleRookSquare[c][s];
308 template<PieceType Pt>
309 inline Bitboard Position::attacks_from(Square s) const {
311 return Pt == BISHOP || Pt == ROOK ? attacks_bb<Pt>(s, pieces())
312 : Pt == QUEEN ? attacks_from<ROOK>(s) | attacks_from<BISHOP>(s)
313 : StepAttacksBB[Pt][s];
317 inline Bitboard Position::attacks_from<PAWN>(Square s, Color c) const {
318 return StepAttacksBB[make_piece(c, PAWN)][s];
321 inline Bitboard Position::attacks_from(Piece p, Square s) const {
322 return attacks_from(p, s, byTypeBB[ALL_PIECES]);
325 inline Bitboard Position::attackers_to(Square s) const {
326 return attackers_to(s, byTypeBB[ALL_PIECES]);
329 inline Bitboard Position::checkers() const {
330 return st->checkersBB;
333 inline Bitboard Position::discovered_check_candidates() const {
334 return hidden_checkers<false>();
337 inline Bitboard Position::pinned_pieces() const {
338 return hidden_checkers<true>();
341 inline bool Position::pawn_is_passed(Color c, Square s) const {
342 return !(pieces(~c, PAWN) & passed_pawn_mask(c, s));
345 inline Key Position::key() const {
349 inline Key Position::exclusion_key() const {
350 return st->key ^ Zobrist::exclusion;
353 inline Key Position::pawn_key() const {
357 inline Key Position::material_key() const {
358 return st->materialKey;
361 inline Score Position::psq_delta(Piece p, Square from, Square to) const {
362 return pieceSquareTable[p][to] - pieceSquareTable[p][from];
365 inline Score Position::psq_score() const {
369 inline Value Position::non_pawn_material(Color c) const {
370 return st->npMaterial[c];
373 inline bool Position::is_passed_pawn_push(Move m) const {
375 return type_of(piece_moved(m)) == PAWN
376 && pawn_is_passed(sideToMove, to_sq(m));
379 inline int Position::game_ply() const {
383 inline bool Position::opposite_bishops() const {
385 return pieceCount[WHITE][BISHOP] == 1
386 && pieceCount[BLACK][BISHOP] == 1
387 && opposite_colors(pieceList[WHITE][BISHOP][0], pieceList[BLACK][BISHOP][0]);
390 inline bool Position::bishop_pair(Color c) const {
392 return pieceCount[c][BISHOP] >= 2
393 && opposite_colors(pieceList[c][BISHOP][0], pieceList[c][BISHOP][1]);
396 inline bool Position::pawn_on_7th(Color c) const {
397 return pieces(c, PAWN) & rank_bb(relative_rank(c, RANK_7));
400 inline bool Position::is_chess960() const {
404 inline bool Position::is_capture_or_promotion(Move m) const {
407 return type_of(m) ? type_of(m) != CASTLE : !is_empty(to_sq(m));
410 inline bool Position::is_capture(Move m) const {
412 // Note that castle is coded as "king captures the rook"
414 return (!is_empty(to_sq(m)) && type_of(m) != CASTLE) || type_of(m) == ENPASSANT;
417 inline PieceType Position::captured_piece_type() const {
418 return st->capturedType;
421 inline Thread* Position::this_thread() const {
425 #endif // !defined(POSITION_H_INCLUDED)