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
29 /// Maximum number of plies per game (220 should be enough, because the
30 /// maximum search depth is 100, and during position setup we reset the
31 /// move counter for every non-reversible move).
32 const int MaxGameLength = 220;
36 /// struct checkInfo is initialized at c'tor time and keeps
37 /// info used to detect if a move gives check.
41 explicit CheckInfo(const Position&);
43 Bitboard dcCandidates;
48 /// Castle rights, encoded as bit fields
66 /// The StateInfo struct stores information we need to restore a Position
67 /// object to its previous state when we retract a move. Whenever a move
68 /// is made on the board (by calling Position::do_move), an StateInfo object
69 /// must be passed as a parameter.
72 Key pawnKey, materialKey;
73 int castleRights, rule50, gamePly, pliesFromNull;
78 PieceType capturedType;
85 /// The position data structure. A position consists of the following data:
87 /// * For each piece type, a bitboard representing the squares occupied
88 /// by pieces of that type.
89 /// * For each color, a bitboard representing the squares occupied by
90 /// pieces of that color.
91 /// * A bitboard of all occupied squares.
92 /// * A bitboard of all checking pieces.
93 /// * A 64-entry array of pieces, indexed by the squares of the board.
94 /// * The current side to move.
95 /// * Information about the castling rights for both sides.
96 /// * The initial files of the kings and both pairs of rooks. This is
97 /// used to implement the Chess960 castling rules.
98 /// * The en passant square (which is SQ_NONE if no en passant capture is
100 /// * The squares of the kings for both sides.
101 /// * Hash keys for the position itself, the current pawn structure, and
102 /// the current material situation.
103 /// * Hash keys for all previous positions in the game for detecting
104 /// repetition draws.
105 /// * A counter for detecting 50 move rule draws.
109 Position(); // No default or copy c'tor allowed
110 Position(const Position& pos);
119 Position(const Position& pos, int threadID);
120 Position(const std::string& fen, bool isChess960, int threadID);
123 void from_fen(const std::string& fen, bool isChess960);
124 const std::string to_fen() const;
125 void print(Move m = MOVE_NONE) const;
130 // The piece on a given square
131 Piece piece_on(Square s) const;
132 Color color_of_piece_on(Square s) const;
133 bool square_is_empty(Square s) const;
134 bool square_is_occupied(Square s) const;
137 Color side_to_move() const;
139 // Bitboard representation of the position
140 Bitboard empty_squares() const;
141 Bitboard occupied_squares() const;
142 Bitboard pieces_of_color(Color c) const;
143 Bitboard pieces(PieceType pt) const;
144 Bitboard pieces(PieceType pt, Color c) const;
145 Bitboard pieces(PieceType pt1, PieceType pt2) const;
146 Bitboard pieces(PieceType pt1, PieceType pt2, Color c) const;
148 // Number of pieces of each color and type
149 int piece_count(Color c, PieceType pt) const;
151 // The en passant square
152 Square ep_square() const;
154 // Current king position for each color
155 Square king_square(Color c) const;
158 bool can_castle_kingside(Color c) const;
159 bool can_castle_queenside(Color c) const;
160 bool can_castle(Color c) const;
161 Square initial_kr_square(Color c) const;
162 Square initial_qr_square(Color c) const;
164 // Bitboards for pinned pieces and discovered check candidates
165 Bitboard discovered_check_candidates(Color c) const;
166 Bitboard pinned_pieces(Color c) const;
168 // Checking pieces and under check information
169 Bitboard checkers() const;
170 bool in_check() const;
173 Square piece_list(Color c, PieceType pt, int index) const;
174 const Square* piece_list_begin(Color c, PieceType pt) const;
176 // Information about attacks to or from a given square
177 Bitboard attackers_to(Square s) const;
178 Bitboard attackers_to(Square s, Bitboard occ) const;
179 Bitboard attacks_from(Piece p, Square s) const;
180 static Bitboard attacks_from(Piece p, Square s, Bitboard occ);
181 template<PieceType> Bitboard attacks_from(Square s) const;
182 template<PieceType> Bitboard attacks_from(Square s, Color c) const;
184 // Properties of moves
185 bool pl_move_is_legal(Move m, Bitboard pinned) const;
186 bool move_is_pl(const Move m) const;
187 bool move_gives_check(Move m, const CheckInfo& ci) const;
188 bool move_is_capture(Move m) const;
189 bool move_is_capture_or_promotion(Move m) const;
190 bool move_is_passed_pawn_push(Move m) const;
191 bool move_attacks_square(Move m, Square s) const;
193 // Piece captured with previous moves
194 PieceType captured_piece_type() const;
196 // Information about pawns
197 bool pawn_is_passed(Color c, Square s) const;
200 bool square_is_weak(Square s, Color c) const;
202 // Doing and undoing moves
203 void do_setup_move(Move m);
204 void do_move(Move m, StateInfo& st);
205 void do_move(Move m, StateInfo& st, const CheckInfo& ci, bool moveIsCheck);
206 void undo_move(Move m);
207 void do_null_move(StateInfo& st);
208 void undo_null_move();
210 // Static exchange evaluation
211 int see(Move m) const;
212 int see_sign(Move m) const;
214 // Accessing hash keys
216 Key get_exclusion_key() const;
217 Key get_pawn_key() const;
218 Key get_material_key() const;
220 // Incremental evaluation
222 Value non_pawn_material(Color c) const;
223 static Score pst_delta(Piece piece, Square from, Square to);
225 // Game termination checks
226 bool is_mate() const;
227 template<bool SkipRepetition> bool is_draw() const;
229 // Number of plies from starting position
230 int startpos_ply_counter() const;
232 // Other properties of the position
233 bool opposite_colored_bishops() const;
234 bool has_pawn_on_7th(Color c) const;
235 bool is_chess960() const;
237 // Current thread ID searching on the position
240 int64_t nodes_searched() const;
241 void set_nodes_searched(int64_t n);
243 // Position consistency check, for debugging
244 bool is_ok(int* failedStep = NULL) const;
246 // Global initialization
251 // Initialization helper functions (used while setting up a position)
254 void put_piece(Piece p, Square s);
255 void set_castle_kingside(Color c);
256 void set_castle_queenside(Color c);
257 bool set_castling_rights(char token);
258 bool move_is_pl_slow(const Move m) const;
260 // Helper functions for doing and undoing moves
261 void do_capture_move(Key& key, PieceType capture, Color them, Square to, bool ep);
262 void do_castle_move(Move m);
263 void undo_castle_move(Move m);
264 void find_checkers();
266 template<bool FindPinned>
267 Bitboard hidden_checkers(Color c) const;
269 // Computing hash keys from scratch (for initialization and debugging)
270 Key compute_key() const;
271 Key compute_pawn_key() const;
272 Key compute_material_key() const;
274 // Computing incremental evaluation scores and material counts
275 static Score pst(Color c, PieceType pt, Square s);
276 Score compute_value() const;
277 Value compute_non_pawn_material(Color c) const;
283 Bitboard byTypeBB[8], byColorBB[2];
286 int pieceCount[2][8]; // [color][pieceType]
289 Square pieceList[2][8][16]; // [color][pieceType][index]
290 int index[64]; // [square]
294 Key history[MaxGameLength];
295 int castleRightsMask[64];
296 StateInfo startState;
297 File initialKFile, initialKRFile, initialQRFile;
299 int startPosPlyCounter;
305 static Key zobrist[2][8][64];
306 static Key zobEp[64];
307 static Key zobCastle[16];
308 static Key zobSideToMove;
309 static Score PieceSquareTable[16][64];
310 static Key zobExclusion;
313 inline int64_t Position::nodes_searched() const {
317 inline void Position::set_nodes_searched(int64_t n) {
321 inline Piece Position::piece_on(Square s) const {
325 inline Color Position::color_of_piece_on(Square s) const {
326 return color_of_piece(piece_on(s));
329 inline bool Position::square_is_empty(Square s) const {
330 return piece_on(s) == PIECE_NONE;
333 inline bool Position::square_is_occupied(Square s) const {
334 return !square_is_empty(s);
337 inline Color Position::side_to_move() const {
341 inline Bitboard Position::occupied_squares() const {
345 inline Bitboard Position::empty_squares() const {
346 return ~occupied_squares();
349 inline Bitboard Position::pieces_of_color(Color c) const {
353 inline Bitboard Position::pieces(PieceType pt) const {
357 inline Bitboard Position::pieces(PieceType pt, Color c) const {
358 return byTypeBB[pt] & byColorBB[c];
361 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2) const {
362 return byTypeBB[pt1] | byTypeBB[pt2];
365 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2, Color c) const {
366 return (byTypeBB[pt1] | byTypeBB[pt2]) & byColorBB[c];
369 inline int Position::piece_count(Color c, PieceType pt) const {
370 return pieceCount[c][pt];
373 inline Square Position::piece_list(Color c, PieceType pt, int idx) const {
374 return pieceList[c][pt][idx];
377 inline const Square* Position::piece_list_begin(Color c, PieceType pt) const {
378 return pieceList[c][pt];
381 inline Square Position::ep_square() const {
385 inline Square Position::king_square(Color c) const {
386 return pieceList[c][KING][0];
389 inline bool Position::can_castle_kingside(Color c) const {
390 return st->castleRights & (WHITE_OO << c);
393 inline bool Position::can_castle_queenside(Color c) const {
394 return st->castleRights & (WHITE_OOO << c);
397 inline bool Position::can_castle(Color c) const {
398 return st->castleRights & ((WHITE_OO | WHITE_OOO) << c);
401 inline void Position::set_castle_kingside(Color c) {
402 st->castleRights |= (WHITE_OO << c);
405 inline void Position::set_castle_queenside(Color c) {
406 st->castleRights |= (WHITE_OOO << c);
409 inline Square Position::initial_kr_square(Color c) const {
410 return relative_square(c, make_square(initialKRFile, RANK_1));
413 inline Square Position::initial_qr_square(Color c) const {
414 return relative_square(c, make_square(initialQRFile, RANK_1));
418 inline Bitboard Position::attacks_from<PAWN>(Square s, Color c) const {
419 return StepAttacksBB[make_piece(c, PAWN)][s];
422 template<PieceType Piece> // Knight and King and white pawns
423 inline Bitboard Position::attacks_from(Square s) const {
424 return StepAttacksBB[Piece][s];
428 inline Bitboard Position::attacks_from<BISHOP>(Square s) const {
429 return bishop_attacks_bb(s, occupied_squares());
433 inline Bitboard Position::attacks_from<ROOK>(Square s) const {
434 return rook_attacks_bb(s, occupied_squares());
438 inline Bitboard Position::attacks_from<QUEEN>(Square s) const {
439 return attacks_from<ROOK>(s) | attacks_from<BISHOP>(s);
442 inline Bitboard Position::checkers() const {
443 return st->checkersBB;
446 inline bool Position::in_check() const {
447 return st->checkersBB != EmptyBoardBB;
450 inline bool Position::pawn_is_passed(Color c, Square s) const {
451 return !(pieces(PAWN, opposite_color(c)) & passed_pawn_mask(c, s));
454 inline bool Position::square_is_weak(Square s, Color c) const {
455 return !(pieces(PAWN, opposite_color(c)) & attack_span_mask(c, s));
458 inline Key Position::get_key() const {
462 inline Key Position::get_exclusion_key() const {
463 return st->key ^ zobExclusion;
466 inline Key Position::get_pawn_key() const {
470 inline Key Position::get_material_key() const {
471 return st->materialKey;
474 inline Score Position::pst(Color c, PieceType pt, Square s) {
475 return PieceSquareTable[make_piece(c, pt)][s];
478 inline Score Position::pst_delta(Piece piece, Square from, Square to) {
479 return PieceSquareTable[piece][to] - PieceSquareTable[piece][from];
482 inline Score Position::value() const {
486 inline Value Position::non_pawn_material(Color c) const {
487 return st->npMaterial[c];
490 inline bool Position::move_is_passed_pawn_push(Move m) const {
492 Color c = side_to_move();
493 return piece_on(move_from(m)) == make_piece(c, PAWN)
494 && pawn_is_passed(c, move_to(m));
497 inline int Position::startpos_ply_counter() const {
498 return startPosPlyCounter;
501 inline bool Position::opposite_colored_bishops() const {
503 return piece_count(WHITE, BISHOP) == 1 && piece_count(BLACK, BISHOP) == 1
504 && opposite_color_squares(piece_list(WHITE, BISHOP, 0), piece_list(BLACK, BISHOP, 0));
507 inline bool Position::has_pawn_on_7th(Color c) const {
508 return pieces(PAWN, c) & rank_bb(relative_rank(c, RANK_7));
511 inline bool Position::is_chess960() const {
515 inline bool Position::move_is_capture_or_promotion(Move m) const {
517 assert(m != MOVE_NONE && m != MOVE_NULL);
518 return move_is_special(m) ? !move_is_castle(m) : !square_is_empty(move_to(m));
521 inline bool Position::move_is_capture(Move m) const {
523 assert(m != MOVE_NONE && m != MOVE_NULL);
525 // Note that castle is coded as "king captures the rook"
526 return (!square_is_empty(move_to(m)) && !move_is_castle(m)) || move_is_ep(m);
529 inline PieceType Position::captured_piece_type() const {
530 return st->capturedType;
533 inline int Position::thread() const {
537 #endif // !defined(POSITION_H_INCLUDED)