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
27 /// Maximum number of plies per game (220 should be enough, because the
28 /// maximum search depth is 100, and during position setup we reset the
29 /// move counter for every non-reversible move).
30 const int MaxGameLength = 220;
34 /// struct checkInfo is initialized at c'tor time and keeps
35 /// info used to detect if a move gives check.
39 explicit CheckInfo(const Position&);
41 Bitboard dcCandidates;
46 /// Castle rights, encoded as bit fields
64 /// The StateInfo struct stores information we need to restore a Position
65 /// object to its previous state when we retract a move. Whenever a move
66 /// is made on the board (by calling Position::do_move), an StateInfo object
67 /// must be passed as a parameter.
70 Key pawnKey, materialKey;
71 int castleRights, rule50, gamePly, pliesFromNull;
76 PieceType capturedType;
83 /// The position data structure. A position consists of the following data:
85 /// * For each piece type, a bitboard representing the squares occupied
86 /// by pieces of that type.
87 /// * For each color, a bitboard representing the squares occupied by
88 /// pieces of that color.
89 /// * A bitboard of all occupied squares.
90 /// * A bitboard of all checking pieces.
91 /// * A 64-entry array of pieces, indexed by the squares of the board.
92 /// * The current side to move.
93 /// * Information about the castling rights for both sides.
94 /// * The initial files of the kings and both pairs of rooks. This is
95 /// used to implement the Chess960 castling rules.
96 /// * The en passant square (which is SQ_NONE if no en passant capture is
98 /// * The squares of the kings for both sides.
99 /// * Hash keys for the position itself, the current pawn structure, and
100 /// the current material situation.
101 /// * Hash keys for all previous positions in the game for detecting
102 /// repetition draws.
103 /// * A counter for detecting 50 move rule draws.
107 Position(); // No default or copy c'tor allowed
108 Position(const Position& pos);
117 Position(const Position& pos, int threadID);
118 Position(const std::string& fen, bool isChess960, int threadID);
121 void from_fen(const std::string& fen, bool isChess960);
122 const std::string to_fen() const;
123 void print(Move m = MOVE_NONE) const;
126 void flipped_copy(const Position& pos);
128 // The piece on a given square
129 Piece piece_on(Square s) const;
130 PieceType type_of_piece_on(Square s) const;
131 Color color_of_piece_on(Square s) const;
132 bool square_is_empty(Square s) const;
133 bool square_is_occupied(Square s) const;
134 Value midgame_value_of_piece_on(Square s) const;
135 Value endgame_value_of_piece_on(Square s) const;
138 Color side_to_move() const;
140 // Bitboard representation of the position
141 Bitboard empty_squares() const;
142 Bitboard occupied_squares() const;
143 Bitboard pieces_of_color(Color c) const;
144 Bitboard pieces(PieceType pt) const;
145 Bitboard pieces(PieceType pt, Color c) const;
146 Bitboard pieces(PieceType pt1, PieceType pt2) const;
147 Bitboard pieces(PieceType pt1, PieceType pt2, Color c) const;
149 // Number of pieces of each color and type
150 int piece_count(Color c, PieceType pt) const;
152 // The en passant square
153 Square ep_square() const;
155 // Current king position for each color
156 Square king_square(Color c) const;
159 bool can_castle_kingside(Color c) const;
160 bool can_castle_queenside(Color c) const;
161 bool can_castle(Color c) const;
162 Square initial_kr_square(Color c) const;
163 Square initial_qr_square(Color c) const;
165 // Bitboards for pinned pieces and discovered check candidates
166 Bitboard discovered_check_candidates(Color c) const;
167 Bitboard pinned_pieces(Color c) const;
169 // Checking pieces and under check information
170 Bitboard checkers() const;
171 bool is_check() const;
174 Square piece_list(Color c, PieceType pt, int index) const;
175 const Square* piece_list_begin(Color c, PieceType pt) const;
177 // Information about attacks to or from a given square
178 Bitboard attackers_to(Square s) 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 pl_move_is_evasion(Move m, Bitboard pinned) const;
187 bool move_is_legal(const Move m) const;
188 bool move_is_legal(const Move m, Bitboard pinned) const;
189 bool move_is_check(Move m) const;
190 bool move_is_check(Move m, const CheckInfo& ci) const;
191 bool move_is_capture(Move m) const;
192 bool move_is_capture_or_promotion(Move m) const;
193 bool move_is_passed_pawn_push(Move m) const;
194 bool move_attacks_square(Move m, Square s) const;
196 // Piece captured with previous moves
197 PieceType captured_piece_type() const;
199 // Information about pawns
200 bool pawn_is_passed(Color c, Square s) const;
203 bool square_is_weak(Square s, Color c) const;
205 // Doing and undoing moves
206 void do_setup_move(Move m);
207 void do_move(Move m, StateInfo& st);
208 void do_move(Move m, StateInfo& st, const CheckInfo& ci, bool moveIsCheck);
209 void undo_move(Move m);
210 void do_null_move(StateInfo& st);
211 void undo_null_move();
213 // Static exchange evaluation
214 int see(Square from, Square to) const;
215 int see(Move m) const;
216 int see_sign(Move m) const;
218 // Accessing hash keys
220 Key get_exclusion_key() const;
221 Key get_pawn_key() const;
222 Key get_material_key() const;
224 // Incremental evaluation
226 Value non_pawn_material(Color c) const;
227 static Score pst_delta(Piece piece, Square from, Square to);
229 // Game termination checks
230 bool is_mate() const;
231 bool is_draw() const;
233 // Number of plies from starting position
234 int startpos_ply_counter() const;
236 // Other properties of the position
237 bool opposite_colored_bishops() const;
238 bool has_pawn_on_7th(Color c) const;
239 bool is_chess960() const;
241 // Current thread ID searching on the position
244 int64_t nodes_searched() const;
245 void set_nodes_searched(int64_t n);
247 // Position consistency check, for debugging
248 bool is_ok(int* failedStep = NULL) const;
250 // Static member functions
251 static void init_zobrist();
252 static void init_piece_square_tables();
256 // Initialization helper functions (used while setting up a position)
259 void put_piece(Piece p, Square s);
260 void do_allow_oo(Color c);
261 void do_allow_ooo(Color c);
262 bool set_castling_rights(char token);
264 // Helper functions for doing and undoing moves
265 void do_capture_move(Key& key, PieceType capture, Color them, Square to, bool ep);
266 void do_castle_move(Move m);
267 void undo_castle_move(Move m);
268 void find_checkers();
270 template<bool FindPinned>
271 Bitboard hidden_checkers(Color c) const;
273 // Computing hash keys from scratch (for initialization and debugging)
274 Key compute_key() const;
275 Key compute_pawn_key() const;
276 Key compute_material_key() const;
278 // Computing incremental evaluation scores and material counts
279 static Score pst(Color c, PieceType pt, Square s);
280 Score compute_value() const;
281 Value compute_non_pawn_material(Color c) const;
287 Bitboard byTypeBB[8], byColorBB[2];
290 int pieceCount[2][8]; // [color][pieceType]
293 Square pieceList[2][8][16]; // [color][pieceType][index]
294 int index[64]; // [square]
298 Key history[MaxGameLength];
299 int castleRightsMask[64];
300 StateInfo startState;
301 File initialKFile, initialKRFile, initialQRFile;
303 int startPosPlyCounter;
309 static Key zobrist[2][8][64];
310 static Key zobEp[64];
311 static Key zobCastle[16];
312 static Key zobSideToMove;
313 static Score PieceSquareTable[16][64];
314 static Key zobExclusion;
315 static const Value seeValues[8];
316 static const Value PieceValueMidgame[17];
317 static const Value PieceValueEndgame[17];
320 inline int64_t Position::nodes_searched() const {
324 inline void Position::set_nodes_searched(int64_t n) {
328 inline Piece Position::piece_on(Square s) const {
332 inline Color Position::color_of_piece_on(Square s) const {
333 return color_of_piece(piece_on(s));
336 inline PieceType Position::type_of_piece_on(Square s) const {
337 return type_of_piece(piece_on(s));
340 inline bool Position::square_is_empty(Square s) const {
341 return piece_on(s) == PIECE_NONE;
344 inline bool Position::square_is_occupied(Square s) const {
345 return !square_is_empty(s);
348 inline Value Position::midgame_value_of_piece_on(Square s) const {
349 return PieceValueMidgame[piece_on(s)];
352 inline Value Position::endgame_value_of_piece_on(Square s) const {
353 return PieceValueEndgame[piece_on(s)];
356 inline Color Position::side_to_move() const {
360 inline Bitboard Position::occupied_squares() const {
364 inline Bitboard Position::empty_squares() const {
365 return ~occupied_squares();
368 inline Bitboard Position::pieces_of_color(Color c) const {
372 inline Bitboard Position::pieces(PieceType pt) const {
376 inline Bitboard Position::pieces(PieceType pt, Color c) const {
377 return byTypeBB[pt] & byColorBB[c];
380 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2) const {
381 return byTypeBB[pt1] | byTypeBB[pt2];
384 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2, Color c) const {
385 return (byTypeBB[pt1] | byTypeBB[pt2]) & byColorBB[c];
388 inline int Position::piece_count(Color c, PieceType pt) const {
389 return pieceCount[c][pt];
392 inline Square Position::piece_list(Color c, PieceType pt, int idx) const {
393 return pieceList[c][pt][idx];
396 inline const Square* Position::piece_list_begin(Color c, PieceType pt) const {
397 return pieceList[c][pt];
400 inline Square Position::ep_square() const {
404 inline Square Position::king_square(Color c) const {
405 return pieceList[c][KING][0];
408 inline bool Position::can_castle_kingside(Color side) const {
409 return st->castleRights & (1+int(side));
412 inline bool Position::can_castle_queenside(Color side) const {
413 return st->castleRights & (4+4*int(side));
416 inline bool Position::can_castle(Color side) const {
417 return can_castle_kingside(side) || can_castle_queenside(side);
420 inline Square Position::initial_kr_square(Color c) const {
421 return relative_square(c, make_square(initialKRFile, RANK_1));
424 inline Square Position::initial_qr_square(Color c) const {
425 return relative_square(c, make_square(initialQRFile, RANK_1));
429 inline Bitboard Position::attacks_from<PAWN>(Square s, Color c) const {
430 return StepAttacksBB[make_piece(c, PAWN)][s];
433 template<PieceType Piece> // Knight and King and white pawns
434 inline Bitboard Position::attacks_from(Square s) const {
435 return StepAttacksBB[Piece][s];
439 inline Bitboard Position::attacks_from<BISHOP>(Square s) const {
440 return bishop_attacks_bb(s, occupied_squares());
444 inline Bitboard Position::attacks_from<ROOK>(Square s) const {
445 return rook_attacks_bb(s, occupied_squares());
449 inline Bitboard Position::attacks_from<QUEEN>(Square s) const {
450 return attacks_from<ROOK>(s) | attacks_from<BISHOP>(s);
453 inline Bitboard Position::checkers() const {
454 return st->checkersBB;
457 inline bool Position::is_check() const {
458 return st->checkersBB != EmptyBoardBB;
461 inline bool Position::pawn_is_passed(Color c, Square s) const {
462 return !(pieces(PAWN, opposite_color(c)) & passed_pawn_mask(c, s));
465 inline bool Position::square_is_weak(Square s, Color c) const {
466 return !(pieces(PAWN, opposite_color(c)) & attack_span_mask(c, s));
469 inline Key Position::get_key() const {
473 inline Key Position::get_exclusion_key() const {
474 return st->key ^ zobExclusion;
477 inline Key Position::get_pawn_key() const {
481 inline Key Position::get_material_key() const {
482 return st->materialKey;
485 inline Score Position::pst(Color c, PieceType pt, Square s) {
486 return PieceSquareTable[make_piece(c, pt)][s];
489 inline Score Position::pst_delta(Piece piece, Square from, Square to) {
490 return PieceSquareTable[piece][to] - PieceSquareTable[piece][from];
493 inline Score Position::value() const {
497 inline Value Position::non_pawn_material(Color c) const {
498 return st->npMaterial[c];
501 inline bool Position::move_is_passed_pawn_push(Move m) const {
503 Color c = side_to_move();
504 return piece_on(move_from(m)) == make_piece(c, PAWN)
505 && pawn_is_passed(c, move_to(m));
508 inline int Position::startpos_ply_counter() const {
509 return startPosPlyCounter;
512 inline bool Position::opposite_colored_bishops() const {
514 return piece_count(WHITE, BISHOP) == 1 && piece_count(BLACK, BISHOP) == 1
515 && opposite_color_squares(piece_list(WHITE, BISHOP, 0), piece_list(BLACK, BISHOP, 0));
518 inline bool Position::has_pawn_on_7th(Color c) const {
519 return pieces(PAWN, c) & rank_bb(relative_rank(c, RANK_7));
522 inline bool Position::is_chess960() const {
526 inline bool Position::move_is_capture(Move m) const {
528 // Move must not be MOVE_NONE !
529 return (m & (3 << 15)) ? !move_is_castle(m) : !square_is_empty(move_to(m));
532 inline bool Position::move_is_capture_or_promotion(Move m) const {
534 // Move must not be MOVE_NONE !
535 return (m & (0x1F << 12)) ? !move_is_castle(m) : !square_is_empty(move_to(m));
538 inline PieceType Position::captured_piece_type() const {
539 return st->capturedType;
542 inline int Position::thread() const {
546 inline void Position::do_allow_oo(Color c) {
547 st->castleRights |= (1 + int(c));
550 inline void Position::do_allow_ooo(Color c) {
551 st->castleRights |= (4 + 4*int(c));
554 #endif // !defined(POSITION_H_INCLUDED)