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 PieceType type_of_piece_on(Square s) const;
133 Color color_of_piece_on(Square s) const;
134 bool square_is_empty(Square s) const;
135 bool square_is_occupied(Square s) const;
136 Value midgame_value_of_piece_on(Square s) const;
137 Value endgame_value_of_piece_on(Square s) const;
140 Color side_to_move() const;
142 // Bitboard representation of the position
143 Bitboard empty_squares() const;
144 Bitboard occupied_squares() const;
145 Bitboard pieces_of_color(Color c) const;
146 Bitboard pieces(PieceType pt) const;
147 Bitboard pieces(PieceType pt, Color c) const;
148 Bitboard pieces(PieceType pt1, PieceType pt2) const;
149 Bitboard pieces(PieceType pt1, PieceType pt2, Color c) const;
151 // Number of pieces of each color and type
152 int piece_count(Color c, PieceType pt) const;
154 // The en passant square
155 Square ep_square() const;
157 // Current king position for each color
158 Square king_square(Color c) const;
161 bool can_castle_kingside(Color c) const;
162 bool can_castle_queenside(Color c) const;
163 bool can_castle(Color c) const;
164 Square initial_kr_square(Color c) const;
165 Square initial_qr_square(Color c) const;
167 // Bitboards for pinned pieces and discovered check candidates
168 Bitboard discovered_check_candidates(Color c) const;
169 Bitboard pinned_pieces(Color c) const;
171 // Checking pieces and under check information
172 Bitboard checkers() const;
173 bool in_check() const;
176 Square piece_list(Color c, PieceType pt, int index) const;
177 const Square* piece_list_begin(Color c, PieceType pt) const;
179 // Information about attacks to or from a given square
180 Bitboard attackers_to(Square s) const;
181 Bitboard attackers_to(Square s, Bitboard occ) const;
182 Bitboard attacks_from(Piece p, Square s) const;
183 static Bitboard attacks_from(Piece p, Square s, Bitboard occ);
184 template<PieceType> Bitboard attacks_from(Square s) const;
185 template<PieceType> Bitboard attacks_from(Square s, Color c) const;
187 // Properties of moves
188 bool pl_move_is_legal(Move m, Bitboard pinned) const;
189 bool move_is_pl(const Move m) const;
190 bool move_gives_check(Move m, const CheckInfo& ci) const;
191 bool move_is_capture(Move m) const;
192 bool move_is_passed_pawn_push(Move m) const;
193 bool move_attacks_square(Move m, Square s) const;
195 // Piece captured with previous moves
196 PieceType captured_piece_type() const;
198 // Information about pawns
199 bool pawn_is_passed(Color c, Square s) const;
202 bool square_is_weak(Square s, Color c) const;
204 // Doing and undoing moves
205 void do_setup_move(Move m);
206 void do_move(Move m, StateInfo& st);
207 void do_move(Move m, StateInfo& st, const CheckInfo& ci, bool moveIsCheck);
208 void undo_move(Move m);
209 void do_null_move(StateInfo& st);
210 void undo_null_move();
212 // Static exchange evaluation
213 int see(Move m) const;
214 int see_sign(Move m) const;
215 static int see_value(PieceType pt);
217 // Accessing hash keys
219 Key get_exclusion_key() const;
220 Key get_pawn_key() const;
221 Key get_material_key() const;
223 // Incremental evaluation
225 Value non_pawn_material(Color c) const;
226 static Score pst_delta(Piece piece, Square from, Square to);
228 // Game termination checks
229 bool is_mate() const;
230 template<bool SkipRepetition> bool is_draw() const;
232 // Number of plies from starting position
233 int startpos_ply_counter() const;
235 // Other properties of the position
236 bool opposite_colored_bishops() const;
237 bool has_pawn_on_7th(Color c) const;
238 bool is_chess960() const;
240 // Current thread ID searching on the position
243 int64_t nodes_searched() const;
244 void set_nodes_searched(int64_t n);
246 // Position consistency check, for debugging
247 bool is_ok(int* failedStep = NULL) const;
249 // Global initialization
254 // Initialization helper functions (used while setting up a position)
257 void put_piece(Piece p, Square s);
258 void set_castle_kingside(Color c);
259 void set_castle_queenside(Color c);
260 bool set_castling_rights(char token);
261 bool move_is_pl_slow(const Move m) const;
263 // Helper functions for doing and undoing moves
264 void do_capture_move(Key& key, PieceType capture, Color them, Square to, bool ep);
265 void do_castle_move(Move m);
266 void undo_castle_move(Move m);
267 void find_checkers();
269 template<bool FindPinned>
270 Bitboard hidden_checkers(Color c) const;
272 // Computing hash keys from scratch (for initialization and debugging)
273 Key compute_key() const;
274 Key compute_pawn_key() const;
275 Key compute_material_key() const;
277 // Computing incremental evaluation scores and material counts
278 static Score pst(Color c, PieceType pt, Square s);
279 Score compute_value() const;
280 Value compute_non_pawn_material(Color c) const;
286 Bitboard byTypeBB[8], byColorBB[2];
289 int pieceCount[2][8]; // [color][pieceType]
292 Square pieceList[2][8][16]; // [color][pieceType][index]
293 int index[64]; // [square]
297 Key history[MaxGameLength];
298 int castleRightsMask[64];
299 StateInfo startState;
300 File initialKFile, initialKRFile, initialQRFile;
302 int startPosPlyCounter;
308 static Key zobrist[2][8][64];
309 static Key zobEp[64];
310 static Key zobCastle[16];
311 static Key zobSideToMove;
312 static Score PieceSquareTable[16][64];
313 static Key zobExclusion;
314 static const Value seeValues[8];
315 static const Value PieceValueMidgame[17];
316 static const Value PieceValueEndgame[17];
319 inline int64_t Position::nodes_searched() const {
323 inline void Position::set_nodes_searched(int64_t n) {
327 inline Piece Position::piece_on(Square s) const {
331 inline Color Position::color_of_piece_on(Square s) const {
332 return color_of_piece(piece_on(s));
335 inline PieceType Position::type_of_piece_on(Square s) const {
336 return type_of_piece(piece_on(s));
339 inline bool Position::square_is_empty(Square s) const {
340 return piece_on(s) == PIECE_NONE;
343 inline bool Position::square_is_occupied(Square s) const {
344 return !square_is_empty(s);
347 inline Value Position::midgame_value_of_piece_on(Square s) const {
348 return PieceValueMidgame[piece_on(s)];
351 inline Value Position::endgame_value_of_piece_on(Square s) const {
352 return PieceValueEndgame[piece_on(s)];
355 inline Color Position::side_to_move() const {
359 inline Bitboard Position::occupied_squares() const {
363 inline Bitboard Position::empty_squares() const {
364 return ~occupied_squares();
367 inline Bitboard Position::pieces_of_color(Color c) const {
371 inline Bitboard Position::pieces(PieceType pt) const {
375 inline Bitboard Position::pieces(PieceType pt, Color c) const {
376 return byTypeBB[pt] & byColorBB[c];
379 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2) const {
380 return byTypeBB[pt1] | byTypeBB[pt2];
383 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2, Color c) const {
384 return (byTypeBB[pt1] | byTypeBB[pt2]) & byColorBB[c];
387 inline int Position::piece_count(Color c, PieceType pt) const {
388 return pieceCount[c][pt];
391 inline Square Position::piece_list(Color c, PieceType pt, int idx) const {
392 return pieceList[c][pt][idx];
395 inline const Square* Position::piece_list_begin(Color c, PieceType pt) const {
396 return pieceList[c][pt];
399 inline Square Position::ep_square() const {
403 inline Square Position::king_square(Color c) const {
404 return pieceList[c][KING][0];
407 inline bool Position::can_castle_kingside(Color c) const {
408 return st->castleRights & (WHITE_OO << c);
411 inline bool Position::can_castle_queenside(Color c) const {
412 return st->castleRights & (WHITE_OOO << c);
415 inline bool Position::can_castle(Color c) const {
416 return st->castleRights & ((WHITE_OO | WHITE_OOO) << c);
419 inline void Position::set_castle_kingside(Color c) {
420 st->castleRights |= (WHITE_OO << c);
423 inline void Position::set_castle_queenside(Color c) {
424 st->castleRights |= (WHITE_OOO << c);
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 StepAttacksBB[make_piece(c, PAWN)][s];
440 template<PieceType Piece> // Knight and King and white pawns
441 inline Bitboard Position::attacks_from(Square s) const {
442 return StepAttacksBB[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::in_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 int Position::see_value(PieceType pt) {
477 return seeValues[pt];
480 inline Key Position::get_key() const {
484 inline Key Position::get_exclusion_key() const {
485 return st->key ^ zobExclusion;
488 inline Key Position::get_pawn_key() const {
492 inline Key Position::get_material_key() const {
493 return st->materialKey;
496 inline Score Position::pst(Color c, PieceType pt, Square s) {
497 return PieceSquareTable[make_piece(c, pt)][s];
500 inline Score Position::pst_delta(Piece piece, Square from, Square to) {
501 return PieceSquareTable[piece][to] - PieceSquareTable[piece][from];
504 inline Score Position::value() const {
508 inline Value Position::non_pawn_material(Color c) const {
509 return st->npMaterial[c];
512 inline bool Position::move_is_passed_pawn_push(Move m) const {
514 Color c = side_to_move();
515 return piece_on(move_from(m)) == make_piece(c, PAWN)
516 && pawn_is_passed(c, move_to(m));
519 inline int Position::startpos_ply_counter() const {
520 return startPosPlyCounter;
523 inline bool Position::opposite_colored_bishops() const {
525 return piece_count(WHITE, BISHOP) == 1 && piece_count(BLACK, BISHOP) == 1
526 && opposite_color_squares(piece_list(WHITE, BISHOP, 0), piece_list(BLACK, BISHOP, 0));
529 inline bool Position::has_pawn_on_7th(Color c) const {
530 return pieces(PAWN, c) & rank_bb(relative_rank(c, RANK_7));
533 inline bool Position::is_chess960() const {
537 inline bool Position::move_is_capture(Move m) const {
539 assert (m != MOVE_NONE && m != MOVE_NULL);
540 return !move_is_special(m) ? !square_is_empty(move_to(m)) : move_is_ep(m);
543 inline PieceType Position::captured_piece_type() const {
544 return st->capturedType;
547 inline int Position::thread() const {
551 #endif // !defined(POSITION_H_INCLUDED)