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 bool square_is_empty(Square s) const;
133 bool square_is_occupied(Square s) const;
136 Color side_to_move() const;
138 // Bitboard representation of the position
139 Bitboard empty_squares() const;
140 Bitboard occupied_squares() const;
141 Bitboard pieces_of_color(Color c) const;
142 Bitboard pieces(PieceType pt) const;
143 Bitboard pieces(PieceType pt, Color c) const;
144 Bitboard pieces(PieceType pt1, PieceType pt2) const;
145 Bitboard pieces(PieceType pt1, PieceType pt2, Color c) const;
147 // Number of pieces of each color and type
148 int piece_count(Color c, PieceType pt) const;
150 // The en passant square
151 Square ep_square() const;
153 // Current king position for each color
154 Square king_square(Color c) const;
157 bool can_castle_kingside(Color c) const;
158 bool can_castle_queenside(Color c) const;
159 bool can_castle(Color c) const;
160 Square initial_kr_square(Color c) const;
161 Square initial_qr_square(Color c) const;
163 // Bitboards for pinned pieces and discovered check candidates
164 Bitboard discovered_check_candidates(Color c) const;
165 Bitboard pinned_pieces(Color c) const;
167 // Checking pieces and under check information
168 Bitboard checkers() const;
169 bool in_check() const;
172 Square piece_list(Color c, PieceType pt, int index) const;
173 const Square* piece_list_begin(Color c, PieceType pt) const;
175 // Information about attacks to or from a given square
176 Bitboard attackers_to(Square s) const;
177 Bitboard attackers_to(Square s, Bitboard occ) const;
178 Bitboard attacks_from(Piece p, Square s) const;
179 static Bitboard attacks_from(Piece p, Square s, Bitboard occ);
180 template<PieceType> Bitboard attacks_from(Square s) const;
181 template<PieceType> Bitboard attacks_from(Square s, Color c) const;
183 // Properties of moves
184 bool pl_move_is_legal(Move m, Bitboard pinned) const;
185 bool move_is_pl(const Move m) const;
186 bool move_gives_check(Move m, const CheckInfo& ci) const;
187 bool move_is_capture(Move m) const;
188 bool move_is_capture_or_promotion(Move m) const;
189 bool move_is_passed_pawn_push(Move m) const;
190 bool move_attacks_square(Move m, Square s) const;
192 // Piece captured with previous moves
193 PieceType captured_piece_type() const;
195 // Information about pawns
196 bool pawn_is_passed(Color c, Square s) const;
199 bool square_is_weak(Square s, Color c) const;
201 // Doing and undoing moves
202 void do_setup_move(Move m);
203 void do_move(Move m, StateInfo& st);
204 void do_move(Move m, StateInfo& st, const CheckInfo& ci, bool moveIsCheck);
205 void undo_move(Move m);
206 void do_null_move(StateInfo& st);
207 void undo_null_move();
209 // Static exchange evaluation
210 int see(Move m) const;
211 int see_sign(Move m) const;
213 // Accessing hash keys
215 Key get_exclusion_key() const;
216 Key get_pawn_key() const;
217 Key get_material_key() const;
219 // Incremental evaluation
221 Value non_pawn_material(Color c) const;
222 static Score pst_delta(Piece piece, Square from, Square to);
224 // Game termination checks
225 bool is_mate() const;
226 template<bool SkipRepetition> bool is_draw() const;
228 // Number of plies from starting position
229 int full_moves() const;
231 // Other properties of the position
232 bool opposite_colored_bishops() const;
233 bool has_pawn_on_7th(Color c) const;
234 bool is_chess960() const;
236 // Current thread ID searching on the position
239 int64_t nodes_searched() const;
240 void set_nodes_searched(int64_t n);
242 // Position consistency check, for debugging
243 bool is_ok(int* failedStep = NULL) const;
245 // Global initialization
250 // Initialization helper functions (used while setting up a position)
253 void put_piece(Piece p, Square s);
254 void set_castle_kingside(Color c);
255 void set_castle_queenside(Color c);
256 void set_castling_rights(char token);
257 bool move_is_pl_slow(const Move m) const;
259 // Helper functions for doing and undoing moves
260 void do_capture_move(Key& key, PieceType capture, Color them, Square to, bool ep);
261 void do_castle_move(Move m);
262 void undo_castle_move(Move m);
263 void find_checkers();
265 template<bool FindPinned>
266 Bitboard hidden_checkers(Color c) const;
268 // Computing hash keys from scratch (for initialization and debugging)
269 Key compute_key() const;
270 Key compute_pawn_key() const;
271 Key compute_material_key() const;
273 // Computing incremental evaluation scores and material counts
274 static Score pst(Color c, PieceType pt, Square s);
275 Score compute_value() const;
276 Value compute_non_pawn_material(Color c) const;
282 Bitboard byTypeBB[8], byColorBB[2];
285 int pieceCount[2][8]; // [color][pieceType]
288 Square pieceList[2][8][16]; // [color][pieceType][index]
289 int index[64]; // [square]
293 Key history[MaxGameLength];
294 int castleRightsMask[64];
295 StateInfo startState;
296 File initialKFile, initialKRFile, initialQRFile;
304 static Key zobrist[2][8][64];
305 static Key zobEp[64];
306 static Key zobCastle[16];
307 static Key zobSideToMove;
308 static Score PieceSquareTable[16][64];
309 static Key zobExclusion;
312 inline int64_t Position::nodes_searched() const {
316 inline void Position::set_nodes_searched(int64_t n) {
320 inline Piece Position::piece_on(Square s) const {
324 inline bool Position::square_is_empty(Square s) const {
325 return piece_on(s) == PIECE_NONE;
328 inline bool Position::square_is_occupied(Square s) const {
329 return !square_is_empty(s);
332 inline Color Position::side_to_move() const {
336 inline Bitboard Position::occupied_squares() const {
340 inline Bitboard Position::empty_squares() const {
341 return ~occupied_squares();
344 inline Bitboard Position::pieces_of_color(Color c) const {
348 inline Bitboard Position::pieces(PieceType pt) const {
352 inline Bitboard Position::pieces(PieceType pt, Color c) const {
353 return byTypeBB[pt] & byColorBB[c];
356 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2) const {
357 return byTypeBB[pt1] | byTypeBB[pt2];
360 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2, Color c) const {
361 return (byTypeBB[pt1] | byTypeBB[pt2]) & byColorBB[c];
364 inline int Position::piece_count(Color c, PieceType pt) const {
365 return pieceCount[c][pt];
368 inline Square Position::piece_list(Color c, PieceType pt, int idx) const {
369 return pieceList[c][pt][idx];
372 inline const Square* Position::piece_list_begin(Color c, PieceType pt) const {
373 return pieceList[c][pt];
376 inline Square Position::ep_square() const {
380 inline Square Position::king_square(Color c) const {
381 return pieceList[c][KING][0];
384 inline bool Position::can_castle_kingside(Color c) const {
385 return st->castleRights & (WHITE_OO << c);
388 inline bool Position::can_castle_queenside(Color c) const {
389 return st->castleRights & (WHITE_OOO << c);
392 inline bool Position::can_castle(Color c) const {
393 return st->castleRights & ((WHITE_OO | WHITE_OOO) << c);
396 inline void Position::set_castle_kingside(Color c) {
397 st->castleRights |= (WHITE_OO << c);
400 inline void Position::set_castle_queenside(Color c) {
401 st->castleRights |= (WHITE_OOO << c);
404 inline Square Position::initial_kr_square(Color c) const {
405 return relative_square(c, make_square(initialKRFile, RANK_1));
408 inline Square Position::initial_qr_square(Color c) const {
409 return relative_square(c, make_square(initialQRFile, RANK_1));
413 inline Bitboard Position::attacks_from<PAWN>(Square s, Color c) const {
414 return StepAttacksBB[make_piece(c, PAWN)][s];
417 template<PieceType Piece> // Knight and King and white pawns
418 inline Bitboard Position::attacks_from(Square s) const {
419 return StepAttacksBB[Piece][s];
423 inline Bitboard Position::attacks_from<BISHOP>(Square s) const {
424 return bishop_attacks_bb(s, occupied_squares());
428 inline Bitboard Position::attacks_from<ROOK>(Square s) const {
429 return rook_attacks_bb(s, occupied_squares());
433 inline Bitboard Position::attacks_from<QUEEN>(Square s) const {
434 return attacks_from<ROOK>(s) | attacks_from<BISHOP>(s);
437 inline Bitboard Position::checkers() const {
438 return st->checkersBB;
441 inline bool Position::in_check() const {
442 return st->checkersBB != EmptyBoardBB;
445 inline bool Position::pawn_is_passed(Color c, Square s) const {
446 return !(pieces(PAWN, opposite_color(c)) & passed_pawn_mask(c, s));
449 inline bool Position::square_is_weak(Square s, Color c) const {
450 return !(pieces(PAWN, opposite_color(c)) & attack_span_mask(c, s));
453 inline Key Position::get_key() const {
457 inline Key Position::get_exclusion_key() const {
458 return st->key ^ zobExclusion;
461 inline Key Position::get_pawn_key() const {
465 inline Key Position::get_material_key() const {
466 return st->materialKey;
469 inline Score Position::pst(Color c, PieceType pt, Square s) {
470 return PieceSquareTable[make_piece(c, pt)][s];
473 inline Score Position::pst_delta(Piece piece, Square from, Square to) {
474 return PieceSquareTable[piece][to] - PieceSquareTable[piece][from];
477 inline Score Position::value() const {
481 inline Value Position::non_pawn_material(Color c) const {
482 return st->npMaterial[c];
485 inline bool Position::move_is_passed_pawn_push(Move m) const {
487 Color c = side_to_move();
488 return piece_on(move_from(m)) == make_piece(c, PAWN)
489 && pawn_is_passed(c, move_to(m));
492 inline int Position::full_moves() const {
496 inline bool Position::opposite_colored_bishops() const {
498 return piece_count(WHITE, BISHOP) == 1 && piece_count(BLACK, BISHOP) == 1
499 && opposite_color_squares(piece_list(WHITE, BISHOP, 0), piece_list(BLACK, BISHOP, 0));
502 inline bool Position::has_pawn_on_7th(Color c) const {
503 return pieces(PAWN, c) & rank_bb(relative_rank(c, RANK_7));
506 inline bool Position::is_chess960() const {
510 inline bool Position::move_is_capture_or_promotion(Move m) const {
512 assert(m != MOVE_NONE && m != MOVE_NULL);
513 return move_is_special(m) ? !move_is_castle(m) : !square_is_empty(move_to(m));
516 inline bool Position::move_is_capture(Move m) const {
518 assert(m != MOVE_NONE && m != MOVE_NULL);
520 // Note that castle is coded as "king captures the rook"
521 return (!square_is_empty(move_to(m)) && !move_is_castle(m)) || move_is_ep(m);
524 inline PieceType Position::captured_piece_type() const {
525 return st->capturedType;
528 inline int Position::thread() const {
532 #endif // !defined(POSITION_H_INCLUDED)