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/>.
21 #if !defined(POSITION_H_INCLUDED)
22 #define POSITION_H_INCLUDED
40 /// Maximum number of plies per game (220 should be enough, because the
41 /// maximum search depth is 100, and during position setup we reset the
42 /// move counter for every non-reversible move).
43 const int MaxGameLength = 220;
52 /// struct checkInfo is initialized at c'tor time and keeps
53 /// info used to detect if a move gives check.
57 explicit CheckInfo(const Position&);
59 Bitboard dcCandidates;
64 /// Castle rights, encoded as bit fields
82 /// The StateInfo struct stores information we need to restore a Position
83 /// object to its previous state when we retract a move. Whenever a move
84 /// is made on the board (by calling Position::do_move), an StateInfo object
85 /// must be passed as a parameter.
88 Key pawnKey, materialKey;
89 int castleRights, rule50, gamePly, pliesFromNull;
94 PieceType capturedType;
101 /// The position data structure. A position consists of the following data:
103 /// * For each piece type, a bitboard representing the squares occupied
104 /// by pieces of that type.
105 /// * For each color, a bitboard representing the squares occupied by
106 /// pieces of that color.
107 /// * A bitboard of all occupied squares.
108 /// * A bitboard of all checking pieces.
109 /// * A 64-entry array of pieces, indexed by the squares of the board.
110 /// * The current side to move.
111 /// * Information about the castling rights for both sides.
112 /// * The initial files of the kings and both pairs of rooks. This is
113 /// used to implement the Chess960 castling rules.
114 /// * The en passant square (which is SQ_NONE if no en passant capture is
116 /// * The squares of the kings for both sides.
117 /// * Hash keys for the position itself, the current pawn structure, and
118 /// the current material situation.
119 /// * Hash keys for all previous positions in the game for detecting
120 /// repetition draws.
121 /// * A counter for detecting 50 move rule draws.
125 friend class MaterialInfo;
126 friend class EndgameFunctions;
128 Position(); // No default or copy c'tor allowed
129 Position(const Position& pos);
138 Position(const Position& pos, int threadID);
139 Position(const std::string& fen, bool isChess960, int threadID);
142 void from_fen(const std::string& fen, bool isChess960);
143 const std::string to_fen() const;
144 void print(Move m = MOVE_NONE) const;
147 void flipped_copy(const Position& pos);
149 // The piece on a given square
150 Piece piece_on(Square s) const;
151 PieceType type_of_piece_on(Square s) const;
152 Color color_of_piece_on(Square s) const;
153 bool square_is_empty(Square s) const;
154 bool square_is_occupied(Square s) const;
155 Value midgame_value_of_piece_on(Square s) const;
156 Value endgame_value_of_piece_on(Square s) const;
159 Color side_to_move() const;
161 // Bitboard representation of the position
162 Bitboard empty_squares() const;
163 Bitboard occupied_squares() const;
164 Bitboard pieces_of_color(Color c) const;
165 Bitboard pieces(PieceType pt) const;
166 Bitboard pieces(PieceType pt, Color c) const;
167 Bitboard pieces(PieceType pt1, PieceType pt2) const;
168 Bitboard pieces(PieceType pt1, PieceType pt2, Color c) const;
170 // Number of pieces of each color and type
171 int piece_count(Color c, PieceType pt) const;
173 // The en passant square
174 Square ep_square() const;
176 // Current king position for each color
177 Square king_square(Color c) const;
180 bool can_castle_kingside(Color c) const;
181 bool can_castle_queenside(Color c) const;
182 bool can_castle(Color c) const;
183 Square initial_kr_square(Color c) const;
184 Square initial_qr_square(Color c) const;
186 // Bitboards for pinned pieces and discovered check candidates
187 Bitboard discovered_check_candidates(Color c) const;
188 Bitboard pinned_pieces(Color c) const;
190 // Checking pieces and under check information
191 Bitboard checkers() const;
192 bool is_check() const;
195 Square piece_list(Color c, PieceType pt, int index) const;
196 const Square* piece_list_begin(Color c, PieceType pt) const;
198 // Information about attacks to or from a given square
199 Bitboard attackers_to(Square s) const;
200 Bitboard attacks_from(Piece p, Square s) const;
201 static Bitboard attacks_from(Piece p, Square s, Bitboard occ);
202 template<PieceType> Bitboard attacks_from(Square s) const;
203 template<PieceType> Bitboard attacks_from(Square s, Color c) const;
205 // Properties of moves
206 bool pl_move_is_legal(Move m, Bitboard pinned) const;
207 bool pl_move_is_evasion(Move m, Bitboard pinned) const;
208 bool move_is_check(Move m) const;
209 bool move_is_check(Move m, const CheckInfo& ci) const;
210 bool move_is_capture(Move m) const;
211 bool move_is_capture_or_promotion(Move m) const;
212 bool move_is_passed_pawn_push(Move m) const;
213 bool move_attacks_square(Move m, Square s) const;
215 // Piece captured with previous moves
216 PieceType captured_piece_type() const;
218 // Information about pawns
219 bool pawn_is_passed(Color c, Square s) const;
222 bool square_is_weak(Square s, Color c) const;
224 // Doing and undoing moves
225 void do_setup_move(Move m);
226 void do_move(Move m, StateInfo& st);
227 void do_move(Move m, StateInfo& st, const CheckInfo& ci, bool moveIsCheck);
228 void undo_move(Move m);
229 void do_null_move(StateInfo& st);
230 void undo_null_move();
232 // Static exchange evaluation
233 int see(Square from, Square to) const;
234 int see(Move m) const;
235 int see_sign(Move m) const;
237 // Accessing hash keys
239 Key get_exclusion_key() const;
240 Key get_pawn_key() const;
241 Key get_material_key() const;
243 // Incremental evaluation
245 Value non_pawn_material(Color c) const;
246 static Score pst_delta(Piece piece, Square from, Square to);
248 // Game termination checks
249 bool is_mate() const;
250 bool is_draw() const;
252 // Check if side to move could be mated in one
253 bool has_mate_threat();
255 // Number of plies from starting position
256 int startpos_ply_counter() const;
258 // Other properties of the position
259 bool opposite_colored_bishops() const;
260 bool has_pawn_on_7th(Color c) const;
261 bool is_chess960() const;
263 // Current thread ID searching on the position
266 int64_t nodes_searched() const;
267 void set_nodes_searched(int64_t n);
269 // Position consistency check, for debugging
270 bool is_ok(int* failedStep = NULL) const;
272 // Static member functions
273 static void init_zobrist();
274 static void init_piece_square_tables();
278 // Initialization helper functions (used while setting up a position)
281 void put_piece(Piece p, Square s);
282 void do_allow_oo(Color c);
283 void do_allow_ooo(Color c);
284 bool set_castling_rights(char token);
286 // Helper functions for doing and undoing moves
287 void do_capture_move(Key& key, PieceType capture, Color them, Square to, bool ep);
288 void do_castle_move(Move m);
289 void undo_castle_move(Move m);
290 void find_checkers();
292 template<bool FindPinned>
293 Bitboard hidden_checkers(Color c) const;
295 // Computing hash keys from scratch (for initialization and debugging)
296 Key compute_key() const;
297 Key compute_pawn_key() const;
298 Key compute_material_key() const;
300 // Computing incremental evaluation scores and material counts
301 static Score pst(Color c, PieceType pt, Square s);
302 Score compute_value() const;
303 Value compute_non_pawn_material(Color c) const;
309 Bitboard byTypeBB[8], byColorBB[2];
312 int pieceCount[2][8]; // [color][pieceType]
315 Square pieceList[2][8][16]; // [color][pieceType][index]
316 int index[64]; // [square]
320 Key history[MaxGameLength];
321 int castleRightsMask[64];
322 StateInfo startState;
323 File initialKFile, initialKRFile, initialQRFile;
325 int startPosPlyCounter;
331 static Key zobrist[2][8][64];
332 static Key zobEp[64];
333 static Key zobCastle[16];
334 static Key zobSideToMove;
335 static Score PieceSquareTable[16][64];
336 static Key zobExclusion;
337 static const Value seeValues[8];
338 static const Value PieceValueMidgame[17];
339 static const Value PieceValueEndgame[17];
344 //// Inline functions
347 inline int64_t Position::nodes_searched() const {
351 inline void Position::set_nodes_searched(int64_t n) {
355 inline Piece Position::piece_on(Square s) const {
359 inline Color Position::color_of_piece_on(Square s) const {
360 return color_of_piece(piece_on(s));
363 inline PieceType Position::type_of_piece_on(Square s) const {
364 return type_of_piece(piece_on(s));
367 inline bool Position::square_is_empty(Square s) const {
368 return piece_on(s) == PIECE_NONE;
371 inline bool Position::square_is_occupied(Square s) const {
372 return !square_is_empty(s);
375 inline Value Position::midgame_value_of_piece_on(Square s) const {
376 return PieceValueMidgame[piece_on(s)];
379 inline Value Position::endgame_value_of_piece_on(Square s) const {
380 return PieceValueEndgame[piece_on(s)];
383 inline Color Position::side_to_move() const {
387 inline Bitboard Position::occupied_squares() const {
391 inline Bitboard Position::empty_squares() const {
392 return ~occupied_squares();
395 inline Bitboard Position::pieces_of_color(Color c) const {
399 inline Bitboard Position::pieces(PieceType pt) const {
403 inline Bitboard Position::pieces(PieceType pt, Color c) const {
404 return byTypeBB[pt] & byColorBB[c];
407 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2) const {
408 return byTypeBB[pt1] | byTypeBB[pt2];
411 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2, Color c) const {
412 return (byTypeBB[pt1] | byTypeBB[pt2]) & byColorBB[c];
415 inline int Position::piece_count(Color c, PieceType pt) const {
416 return pieceCount[c][pt];
419 inline Square Position::piece_list(Color c, PieceType pt, int idx) const {
420 return pieceList[c][pt][idx];
423 inline const Square* Position::piece_list_begin(Color c, PieceType pt) const {
424 return pieceList[c][pt];
427 inline Square Position::ep_square() const {
431 inline Square Position::king_square(Color c) const {
432 return pieceList[c][KING][0];
435 inline bool Position::can_castle_kingside(Color side) const {
436 return st->castleRights & (1+int(side));
439 inline bool Position::can_castle_queenside(Color side) const {
440 return st->castleRights & (4+4*int(side));
443 inline bool Position::can_castle(Color side) const {
444 return can_castle_kingside(side) || can_castle_queenside(side);
447 inline Square Position::initial_kr_square(Color c) const {
448 return relative_square(c, make_square(initialKRFile, RANK_1));
451 inline Square Position::initial_qr_square(Color c) const {
452 return relative_square(c, make_square(initialQRFile, RANK_1));
456 inline Bitboard Position::attacks_from<PAWN>(Square s, Color c) const {
457 return NonSlidingAttacksBB[piece_of_color_and_type(c, PAWN)][s];
460 template<PieceType Piece> // Knight and King and white pawns
461 inline Bitboard Position::attacks_from(Square s) const {
462 return NonSlidingAttacksBB[Piece][s];
466 inline Bitboard Position::attacks_from<BISHOP>(Square s) const {
467 return bishop_attacks_bb(s, occupied_squares());
471 inline Bitboard Position::attacks_from<ROOK>(Square s) const {
472 return rook_attacks_bb(s, occupied_squares());
476 inline Bitboard Position::attacks_from<QUEEN>(Square s) const {
477 return attacks_from<ROOK>(s) | attacks_from<BISHOP>(s);
480 inline Bitboard Position::checkers() const {
481 return st->checkersBB;
484 inline bool Position::is_check() const {
485 return st->checkersBB != EmptyBoardBB;
488 inline bool Position::pawn_is_passed(Color c, Square s) const {
489 return !(pieces(PAWN, opposite_color(c)) & passed_pawn_mask(c, s));
492 inline bool Position::square_is_weak(Square s, Color c) const {
493 return !(pieces(PAWN, opposite_color(c)) & attack_span_mask(c, s));
496 inline Key Position::get_key() const {
500 inline Key Position::get_exclusion_key() const {
501 return st->key ^ zobExclusion;
504 inline Key Position::get_pawn_key() const {
508 inline Key Position::get_material_key() const {
509 return st->materialKey;
512 inline Score Position::pst(Color c, PieceType pt, Square s) {
513 return PieceSquareTable[piece_of_color_and_type(c, pt)][s];
516 inline Score Position::pst_delta(Piece piece, Square from, Square to) {
517 return PieceSquareTable[piece][to] - PieceSquareTable[piece][from];
520 inline Score Position::value() const {
524 inline Value Position::non_pawn_material(Color c) const {
525 return st->npMaterial[c];
528 inline bool Position::move_is_passed_pawn_push(Move m) const {
530 Color c = side_to_move();
531 return piece_on(move_from(m)) == piece_of_color_and_type(c, PAWN)
532 && pawn_is_passed(c, move_to(m));
535 inline int Position::startpos_ply_counter() const {
536 return startPosPlyCounter;
539 inline bool Position::opposite_colored_bishops() const {
541 return piece_count(WHITE, BISHOP) == 1
542 && piece_count(BLACK, BISHOP) == 1
543 && !same_color_squares(piece_list(WHITE, BISHOP, 0), piece_list(BLACK, BISHOP, 0));
546 inline bool Position::has_pawn_on_7th(Color c) const {
547 return pieces(PAWN, c) & relative_rank_bb(c, RANK_7);
550 inline bool Position::is_chess960() const {
554 inline bool Position::move_is_capture(Move m) const {
556 // Move must not be MOVE_NONE !
557 return (m & (3 << 15)) ? !move_is_castle(m) : !square_is_empty(move_to(m));
560 inline bool Position::move_is_capture_or_promotion(Move m) const {
562 // Move must not be MOVE_NONE !
563 return (m & (0x1F << 12)) ? !move_is_castle(m) : !square_is_empty(move_to(m));
566 inline PieceType Position::captured_piece_type() const {
567 return st->capturedType;
570 inline int Position::thread() const {
574 inline void Position::do_allow_oo(Color c) {
575 st->castleRights |= (1 + int(c));
578 inline void Position::do_allow_ooo(Color c) {
579 st->castleRights |= (4 + 4*int(c));
582 #endif // !defined(POSITION_H_INCLUDED)