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;
135 Color side_to_move() const;
137 // Bitboard representation of the position
138 Bitboard empty_squares() const;
139 Bitboard occupied_squares() const;
140 Bitboard pieces(Color c) const;
141 Bitboard pieces(PieceType pt) const;
142 Bitboard pieces(PieceType pt, Color c) const;
143 Bitboard pieces(PieceType pt1, PieceType pt2) const;
144 Bitboard pieces(PieceType pt1, PieceType pt2, Color c) const;
146 // Number of pieces of each color and type
147 int piece_count(Color c, PieceType pt) const;
149 // The en passant square
150 Square ep_square() const;
152 // Current king position for each color
153 Square king_square(Color c) const;
156 bool can_castle(CastleRight f) const;
157 bool can_castle(Color c) const;
158 Square castle_rook_square(CastleRight f) const;
160 // Bitboards for pinned pieces and discovered check candidates
161 Bitboard discovered_check_candidates(Color c) const;
162 Bitboard pinned_pieces(Color c) const;
164 // Checking pieces and under check information
165 Bitboard checkers() const;
166 bool in_check() const;
169 const Square* piece_list(Color c, PieceType pt) const;
171 // Information about attacks to or from a given square
172 Bitboard attackers_to(Square s) const;
173 Bitboard attackers_to(Square s, Bitboard occ) const;
174 Bitboard attacks_from(Piece p, Square s) const;
175 static Bitboard attacks_from(Piece p, Square s, Bitboard occ);
176 template<PieceType> Bitboard attacks_from(Square s) const;
177 template<PieceType> Bitboard attacks_from(Square s, Color c) const;
179 // Properties of moves
180 bool pl_move_is_legal(Move m, Bitboard pinned) const;
181 bool move_is_pl(const Move m) const;
182 bool move_gives_check(Move m, const CheckInfo& ci) const;
183 bool move_is_capture(Move m) const;
184 bool move_is_capture_or_promotion(Move m) const;
185 bool move_is_passed_pawn_push(Move m) const;
186 bool move_attacks_square(Move m, Square s) const;
188 // Piece captured with previous moves
189 PieceType captured_piece_type() const;
191 // Information about pawns
192 bool pawn_is_passed(Color c, Square s) const;
194 // Doing and undoing moves
195 void do_setup_move(Move m);
196 void do_move(Move m, StateInfo& st);
197 void do_move(Move m, StateInfo& st, const CheckInfo& ci, bool moveIsCheck);
198 void undo_move(Move m);
199 void do_null_move(StateInfo& st);
200 void undo_null_move();
202 // Static exchange evaluation
203 int see(Move m) const;
204 int see_sign(Move m) const;
206 // Accessing hash keys
208 Key get_exclusion_key() const;
209 Key get_pawn_key() const;
210 Key get_material_key() const;
212 // Incremental evaluation
214 Value non_pawn_material(Color c) const;
215 Score pst_delta(Piece piece, Square from, Square to) const;
217 // Game termination checks
218 bool is_mate() const;
219 template<bool SkipRepetition> bool is_draw() const;
221 // Number of plies from starting position
222 int full_moves() const;
224 // Other properties of the position
225 bool opposite_colored_bishops() const;
226 bool has_pawn_on_7th(Color c) const;
227 bool is_chess960() const;
229 // Current thread ID searching on the position
232 int64_t nodes_searched() const;
233 void set_nodes_searched(int64_t n);
235 // Position consistency check, for debugging
236 bool is_ok(int* failedStep = NULL) const;
238 // Global initialization
243 // Initialization helper functions (used while setting up a position)
246 void put_piece(Piece p, Square s);
247 void set_castle(int f, Square ksq, Square rsq);
248 void set_castling_rights(char token);
249 bool move_is_pl_slow(const Move m) const;
251 // Helper functions for doing and undoing moves
252 void do_capture_move(Key& key, PieceType capture, Color them, Square to, bool ep);
253 void do_castle_move(Move m);
254 void undo_castle_move(Move m);
255 void find_checkers();
257 template<bool FindPinned>
258 Bitboard hidden_checkers(Color c) const;
260 // Computing hash keys from scratch (for initialization and debugging)
261 Key compute_key() const;
262 Key compute_pawn_key() const;
263 Key compute_material_key() const;
265 // Computing incremental evaluation scores and material counts
266 Score pst(Piece p, Square s) const;
267 Score compute_value() const;
268 Value compute_non_pawn_material(Color c) const;
274 Bitboard byTypeBB[8], byColorBB[2];
277 int pieceCount[2][8]; // [color][pieceType]
280 Square pieceList[2][8][16]; // [color][pieceType][index]
281 int index[64]; // [square]
285 Key history[MaxGameLength];
286 int castleRightsMask[64];
287 Square castleRookSquare[16]; // [CastleRights]
288 StateInfo startState;
296 static Key zobrist[2][8][64];
297 static Key zobEp[64];
298 static Key zobCastle[16];
299 static Key zobSideToMove;
300 static Score PieceSquareTable[16][64];
301 static Key zobExclusion;
304 inline int64_t Position::nodes_searched() const {
308 inline void Position::set_nodes_searched(int64_t n) {
312 inline Piece Position::piece_on(Square s) const {
316 inline bool Position::square_is_empty(Square s) const {
317 return piece_on(s) == PIECE_NONE;
320 inline Color Position::side_to_move() const {
324 inline Bitboard Position::occupied_squares() const {
328 inline Bitboard Position::empty_squares() const {
329 return ~occupied_squares();
332 inline Bitboard Position::pieces(Color c) const {
336 inline Bitboard Position::pieces(PieceType pt) const {
340 inline Bitboard Position::pieces(PieceType pt, Color c) const {
341 return byTypeBB[pt] & byColorBB[c];
344 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2) const {
345 return byTypeBB[pt1] | byTypeBB[pt2];
348 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2, Color c) const {
349 return (byTypeBB[pt1] | byTypeBB[pt2]) & byColorBB[c];
352 inline int Position::piece_count(Color c, PieceType pt) const {
353 return pieceCount[c][pt];
356 inline const Square* Position::piece_list(Color c, PieceType pt) const {
357 return pieceList[c][pt];
360 inline Square Position::ep_square() const {
364 inline Square Position::king_square(Color c) const {
365 return pieceList[c][KING][0];
368 inline bool Position::can_castle(CastleRight f) const {
369 return st->castleRights & f;
372 inline bool Position::can_castle(Color c) const {
373 return st->castleRights & ((WHITE_OO | WHITE_OOO) << c);
376 inline Square Position::castle_rook_square(CastleRight f) const {
377 return castleRookSquare[f];
381 inline Bitboard Position::attacks_from<PAWN>(Square s, Color c) const {
382 return StepAttacksBB[make_piece(c, PAWN)][s];
385 template<PieceType Piece> // Knight and King and white pawns
386 inline Bitboard Position::attacks_from(Square s) const {
387 return StepAttacksBB[Piece][s];
391 inline Bitboard Position::attacks_from<BISHOP>(Square s) const {
392 return bishop_attacks_bb(s, occupied_squares());
396 inline Bitboard Position::attacks_from<ROOK>(Square s) const {
397 return rook_attacks_bb(s, occupied_squares());
401 inline Bitboard Position::attacks_from<QUEEN>(Square s) const {
402 return attacks_from<ROOK>(s) | attacks_from<BISHOP>(s);
405 inline Bitboard Position::checkers() const {
406 return st->checkersBB;
409 inline bool Position::in_check() const {
410 return st->checkersBB != EmptyBoardBB;
413 inline bool Position::pawn_is_passed(Color c, Square s) const {
414 return !(pieces(PAWN, opposite_color(c)) & passed_pawn_mask(c, s));
417 inline Key Position::get_key() const {
421 inline Key Position::get_exclusion_key() const {
422 return st->key ^ zobExclusion;
425 inline Key Position::get_pawn_key() const {
429 inline Key Position::get_material_key() const {
430 return st->materialKey;
433 inline Score Position::pst(Piece p, Square s) const {
434 return PieceSquareTable[p][s];
437 inline Score Position::pst_delta(Piece piece, Square from, Square to) const {
438 return PieceSquareTable[piece][to] - PieceSquareTable[piece][from];
441 inline Score Position::value() const {
445 inline Value Position::non_pawn_material(Color c) const {
446 return st->npMaterial[c];
449 inline bool Position::move_is_passed_pawn_push(Move m) const {
451 Color c = side_to_move();
452 return piece_on(move_from(m)) == make_piece(c, PAWN)
453 && pawn_is_passed(c, move_to(m));
456 inline int Position::full_moves() const {
460 inline bool Position::opposite_colored_bishops() const {
462 return piece_count(WHITE, BISHOP) == 1
463 && piece_count(BLACK, BISHOP) == 1
464 && opposite_color_squares(piece_list(WHITE, BISHOP)[0], piece_list(BLACK, BISHOP)[0]);
467 inline bool Position::has_pawn_on_7th(Color c) const {
468 return pieces(PAWN, c) & rank_bb(relative_rank(c, RANK_7));
471 inline bool Position::is_chess960() const {
475 inline bool Position::move_is_capture_or_promotion(Move m) const {
477 assert(m != MOVE_NONE && m != MOVE_NULL);
478 return move_is_special(m) ? !move_is_castle(m) : !square_is_empty(move_to(m));
481 inline bool Position::move_is_capture(Move m) const {
483 assert(m != MOVE_NONE && m != MOVE_NULL);
485 // Note that castle is coded as "king captures the rook"
486 return (!square_is_empty(move_to(m)) && !move_is_castle(m)) || move_is_ep(m);
489 inline PieceType Position::captured_piece_type() const {
490 return st->capturedType;
493 inline int Position::thread() const {
497 #endif // !defined(POSITION_H_INCLUDED)