2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2010 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 /// Maximum number of plies per game (220 should be enough, because the
31 /// maximum search depth is 100, and during position setup we reset the
32 /// move counter for every non-reversible move).
33 const int MaxGameLength = 220;
37 /// struct checkInfo is initialized at c'tor time and keeps
38 /// info used to detect if a move gives check.
42 explicit CheckInfo(const Position&);
44 Bitboard dcCandidates;
49 /// Castle rights, encoded as bit fields
67 /// The StateInfo struct stores information we need to restore a Position
68 /// object to its previous state when we retract a move. Whenever a move
69 /// is made on the board (by calling Position::do_move), an StateInfo object
70 /// must be passed as a parameter.
73 Key pawnKey, materialKey;
74 int castleRights, rule50, gamePly, pliesFromNull;
79 PieceType capturedType;
86 /// The position data structure. A position consists of the following data:
88 /// * For each piece type, a bitboard representing the squares occupied
89 /// by pieces of that type.
90 /// * For each color, a bitboard representing the squares occupied by
91 /// pieces of that color.
92 /// * A bitboard of all occupied squares.
93 /// * A bitboard of all checking pieces.
94 /// * A 64-entry array of pieces, indexed by the squares of the board.
95 /// * The current side to move.
96 /// * Information about the castling rights for both sides.
97 /// * The initial files of the kings and both pairs of rooks. This is
98 /// used to implement the Chess960 castling rules.
99 /// * The en passant square (which is SQ_NONE if no en passant capture is
101 /// * The squares of the kings for both sides.
102 /// * Hash keys for the position itself, the current pawn structure, and
103 /// the current material situation.
104 /// * Hash keys for all previous positions in the game for detecting
105 /// repetition draws.
106 /// * A counter for detecting 50 move rule draws.
110 friend class MaterialInfo;
111 friend class EndgameFunctions;
113 Position(); // No default or copy c'tor allowed
114 Position(const Position& pos);
123 Position(const Position& pos, int threadID);
124 Position(const std::string& fen, bool isChess960, int threadID);
127 void from_fen(const std::string& fen, bool isChess960);
128 const std::string to_fen() const;
129 void print(Move m = MOVE_NONE) const;
132 void flipped_copy(const Position& pos);
134 // The piece on a given square
135 Piece piece_on(Square s) const;
136 PieceType type_of_piece_on(Square s) const;
137 Color color_of_piece_on(Square s) const;
138 bool square_is_empty(Square s) const;
139 bool square_is_occupied(Square s) const;
140 Value midgame_value_of_piece_on(Square s) const;
141 Value endgame_value_of_piece_on(Square s) const;
144 Color side_to_move() const;
146 // Bitboard representation of the position
147 Bitboard empty_squares() const;
148 Bitboard occupied_squares() const;
149 Bitboard pieces_of_color(Color c) const;
150 Bitboard pieces(PieceType pt) const;
151 Bitboard pieces(PieceType pt, Color c) const;
152 Bitboard pieces(PieceType pt1, PieceType pt2) const;
153 Bitboard pieces(PieceType pt1, PieceType pt2, Color c) const;
155 // Number of pieces of each color and type
156 int piece_count(Color c, PieceType pt) const;
158 // The en passant square
159 Square ep_square() const;
161 // Current king position for each color
162 Square king_square(Color c) const;
165 bool can_castle_kingside(Color c) const;
166 bool can_castle_queenside(Color c) const;
167 bool can_castle(Color c) const;
168 Square initial_kr_square(Color c) const;
169 Square initial_qr_square(Color c) const;
171 // Bitboards for pinned pieces and discovered check candidates
172 Bitboard discovered_check_candidates(Color c) const;
173 Bitboard pinned_pieces(Color c) const;
175 // Checking pieces and under check information
176 Bitboard checkers() const;
177 bool is_check() const;
180 Square piece_list(Color c, PieceType pt, int index) const;
181 const Square* piece_list_begin(Color c, PieceType pt) const;
183 // Information about attacks to or from a given square
184 Bitboard attackers_to(Square s) const;
185 Bitboard attacks_from(Piece p, Square s) const;
186 static Bitboard attacks_from(Piece p, Square s, Bitboard occ);
187 template<PieceType> Bitboard attacks_from(Square s) const;
188 template<PieceType> Bitboard attacks_from(Square s, Color c) const;
190 // Properties of moves
191 bool pl_move_is_legal(Move m, Bitboard pinned) const;
192 bool pl_move_is_evasion(Move m, Bitboard pinned) const;
193 bool move_is_check(Move m) const;
194 bool move_is_check(Move m, const CheckInfo& ci) const;
195 bool move_is_capture(Move m) const;
196 bool move_is_capture_or_promotion(Move m) const;
197 bool move_is_passed_pawn_push(Move m) const;
198 bool move_attacks_square(Move m, Square s) const;
200 // Piece captured with previous moves
201 PieceType captured_piece_type() const;
203 // Information about pawns
204 bool pawn_is_passed(Color c, Square s) const;
207 bool square_is_weak(Square s, Color c) const;
209 // Doing and undoing moves
210 void do_setup_move(Move m);
211 void do_move(Move m, StateInfo& st);
212 void do_move(Move m, StateInfo& st, const CheckInfo& ci, bool moveIsCheck);
213 void undo_move(Move m);
214 void do_null_move(StateInfo& st);
215 void undo_null_move();
217 // Static exchange evaluation
218 int see(Square from, Square to) const;
219 int see(Move m) const;
220 int see_sign(Move m) const;
222 // Accessing hash keys
224 Key get_exclusion_key() const;
225 Key get_pawn_key() const;
226 Key get_material_key() const;
228 // Incremental evaluation
230 Value non_pawn_material(Color c) const;
231 static Score pst_delta(Piece piece, Square from, Square to);
233 // Game termination checks
234 bool is_mate() const;
235 bool is_draw() const;
237 // Check if side to move could be mated in one
238 bool has_mate_threat();
240 // Number of plies from starting position
241 int startpos_ply_counter() const;
243 // Other properties of the position
244 bool opposite_colored_bishops() const;
245 bool has_pawn_on_7th(Color c) const;
246 bool is_chess960() const;
248 // Current thread ID searching on the position
251 int64_t nodes_searched() const;
252 void set_nodes_searched(int64_t n);
254 // Position consistency check, for debugging
255 bool is_ok(int* failedStep = NULL) const;
257 // Static member functions
258 static void init_zobrist();
259 static void init_piece_square_tables();
263 // Initialization helper functions (used while setting up a position)
266 void put_piece(Piece p, Square s);
267 void do_allow_oo(Color c);
268 void do_allow_ooo(Color c);
269 bool set_castling_rights(char token);
271 // Helper functions for doing and undoing moves
272 void do_capture_move(Key& key, PieceType capture, Color them, Square to, bool ep);
273 void do_castle_move(Move m);
274 void undo_castle_move(Move m);
275 void find_checkers();
277 template<bool FindPinned>
278 Bitboard hidden_checkers(Color c) const;
280 // Computing hash keys from scratch (for initialization and debugging)
281 Key compute_key() const;
282 Key compute_pawn_key() const;
283 Key compute_material_key() const;
285 // Computing incremental evaluation scores and material counts
286 static Score pst(Color c, PieceType pt, Square s);
287 Score compute_value() const;
288 Value compute_non_pawn_material(Color c) const;
294 Bitboard byTypeBB[8], byColorBB[2];
297 int pieceCount[2][8]; // [color][pieceType]
300 Square pieceList[2][8][16]; // [color][pieceType][index]
301 int index[64]; // [square]
305 Key history[MaxGameLength];
306 int castleRightsMask[64];
307 StateInfo startState;
308 File initialKFile, initialKRFile, initialQRFile;
310 int startPosPlyCounter;
316 static Key zobrist[2][8][64];
317 static Key zobEp[64];
318 static Key zobCastle[16];
319 static Key zobSideToMove;
320 static Score PieceSquareTable[16][64];
321 static Key zobExclusion;
322 static const Value seeValues[8];
323 static const Value PieceValueMidgame[17];
324 static const Value PieceValueEndgame[17];
327 inline int64_t Position::nodes_searched() const {
331 inline void Position::set_nodes_searched(int64_t n) {
335 inline Piece Position::piece_on(Square s) const {
339 inline Color Position::color_of_piece_on(Square s) const {
340 return color_of_piece(piece_on(s));
343 inline PieceType Position::type_of_piece_on(Square s) const {
344 return type_of_piece(piece_on(s));
347 inline bool Position::square_is_empty(Square s) const {
348 return piece_on(s) == PIECE_NONE;
351 inline bool Position::square_is_occupied(Square s) const {
352 return !square_is_empty(s);
355 inline Value Position::midgame_value_of_piece_on(Square s) const {
356 return PieceValueMidgame[piece_on(s)];
359 inline Value Position::endgame_value_of_piece_on(Square s) const {
360 return PieceValueEndgame[piece_on(s)];
363 inline Color Position::side_to_move() const {
367 inline Bitboard Position::occupied_squares() const {
371 inline Bitboard Position::empty_squares() const {
372 return ~occupied_squares();
375 inline Bitboard Position::pieces_of_color(Color c) const {
379 inline Bitboard Position::pieces(PieceType pt) const {
383 inline Bitboard Position::pieces(PieceType pt, Color c) const {
384 return byTypeBB[pt] & byColorBB[c];
387 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2) const {
388 return byTypeBB[pt1] | byTypeBB[pt2];
391 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2, Color c) const {
392 return (byTypeBB[pt1] | byTypeBB[pt2]) & byColorBB[c];
395 inline int Position::piece_count(Color c, PieceType pt) const {
396 return pieceCount[c][pt];
399 inline Square Position::piece_list(Color c, PieceType pt, int idx) const {
400 return pieceList[c][pt][idx];
403 inline const Square* Position::piece_list_begin(Color c, PieceType pt) const {
404 return pieceList[c][pt];
407 inline Square Position::ep_square() const {
411 inline Square Position::king_square(Color c) const {
412 return pieceList[c][KING][0];
415 inline bool Position::can_castle_kingside(Color side) const {
416 return st->castleRights & (1+int(side));
419 inline bool Position::can_castle_queenside(Color side) const {
420 return st->castleRights & (4+4*int(side));
423 inline bool Position::can_castle(Color side) const {
424 return can_castle_kingside(side) || can_castle_queenside(side);
427 inline Square Position::initial_kr_square(Color c) const {
428 return relative_square(c, make_square(initialKRFile, RANK_1));
431 inline Square Position::initial_qr_square(Color c) const {
432 return relative_square(c, make_square(initialQRFile, RANK_1));
436 inline Bitboard Position::attacks_from<PAWN>(Square s, Color c) const {
437 return NonSlidingAttacksBB[piece_of_color_and_type(c, PAWN)][s];
440 template<PieceType Piece> // Knight and King and white pawns
441 inline Bitboard Position::attacks_from(Square s) const {
442 return NonSlidingAttacksBB[Piece][s];
446 inline Bitboard Position::attacks_from<BISHOP>(Square s) const {
447 return bishop_attacks_bb(s, occupied_squares());
451 inline Bitboard Position::attacks_from<ROOK>(Square s) const {
452 return rook_attacks_bb(s, occupied_squares());
456 inline Bitboard Position::attacks_from<QUEEN>(Square s) const {
457 return attacks_from<ROOK>(s) | attacks_from<BISHOP>(s);
460 inline Bitboard Position::checkers() const {
461 return st->checkersBB;
464 inline bool Position::is_check() const {
465 return st->checkersBB != EmptyBoardBB;
468 inline bool Position::pawn_is_passed(Color c, Square s) const {
469 return !(pieces(PAWN, opposite_color(c)) & passed_pawn_mask(c, s));
472 inline bool Position::square_is_weak(Square s, Color c) const {
473 return !(pieces(PAWN, opposite_color(c)) & attack_span_mask(c, s));
476 inline Key Position::get_key() const {
480 inline Key Position::get_exclusion_key() const {
481 return st->key ^ zobExclusion;
484 inline Key Position::get_pawn_key() const {
488 inline Key Position::get_material_key() const {
489 return st->materialKey;
492 inline Score Position::pst(Color c, PieceType pt, Square s) {
493 return PieceSquareTable[piece_of_color_and_type(c, pt)][s];
496 inline Score Position::pst_delta(Piece piece, Square from, Square to) {
497 return PieceSquareTable[piece][to] - PieceSquareTable[piece][from];
500 inline Score Position::value() const {
504 inline Value Position::non_pawn_material(Color c) const {
505 return st->npMaterial[c];
508 inline bool Position::move_is_passed_pawn_push(Move m) const {
510 Color c = side_to_move();
511 return piece_on(move_from(m)) == piece_of_color_and_type(c, PAWN)
512 && pawn_is_passed(c, move_to(m));
515 inline int Position::startpos_ply_counter() const {
516 return startPosPlyCounter;
519 inline bool Position::opposite_colored_bishops() const {
521 return piece_count(WHITE, BISHOP) == 1 && piece_count(BLACK, BISHOP) == 1
522 && opposite_color_squares(piece_list(WHITE, BISHOP, 0), piece_list(BLACK, BISHOP, 0));
525 inline bool Position::has_pawn_on_7th(Color c) const {
526 return pieces(PAWN, c) & rank_bb(relative_rank(c, RANK_7));
529 inline bool Position::is_chess960() const {
533 inline bool Position::move_is_capture(Move m) const {
535 // Move must not be MOVE_NONE !
536 return (m & (3 << 15)) ? !move_is_castle(m) : !square_is_empty(move_to(m));
539 inline bool Position::move_is_capture_or_promotion(Move m) const {
541 // Move must not be MOVE_NONE !
542 return (m & (0x1F << 12)) ? !move_is_castle(m) : !square_is_empty(move_to(m));
545 inline PieceType Position::captured_piece_type() const {
546 return st->capturedType;
549 inline int Position::thread() const {
553 inline void Position::do_allow_oo(Color c) {
554 st->castleRights |= (1 + int(c));
557 inline void Position::do_allow_ooo(Color c) {
558 st->castleRights |= (4 + 4*int(c));
561 #endif // !defined(POSITION_H_INCLUDED)