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 friend class MaterialInfo;
110 friend class EndgameFunctions;
112 Position(); // No default or copy c'tor allowed
113 Position(const Position& pos);
122 Position(const Position& pos, int threadID);
123 Position(const std::string& fen, bool isChess960, int threadID);
126 void from_fen(const std::string& fen, bool isChess960);
127 const std::string to_fen() const;
128 void print(Move m = MOVE_NONE) const;
131 void flipped_copy(const Position& pos);
133 // The piece on a given square
134 Piece piece_on(Square s) const;
135 PieceType type_of_piece_on(Square s) const;
136 Color color_of_piece_on(Square s) const;
137 bool square_is_empty(Square s) const;
138 bool square_is_occupied(Square s) const;
139 Value midgame_value_of_piece_on(Square s) const;
140 Value endgame_value_of_piece_on(Square s) const;
143 Color side_to_move() const;
145 // Bitboard representation of the position
146 Bitboard empty_squares() const;
147 Bitboard occupied_squares() const;
148 Bitboard pieces_of_color(Color c) const;
149 Bitboard pieces(PieceType pt) const;
150 Bitboard pieces(PieceType pt, Color c) const;
151 Bitboard pieces(PieceType pt1, PieceType pt2) const;
152 Bitboard pieces(PieceType pt1, PieceType pt2, Color c) const;
154 // Number of pieces of each color and type
155 int piece_count(Color c, PieceType pt) const;
157 // The en passant square
158 Square ep_square() const;
160 // Current king position for each color
161 Square king_square(Color c) const;
164 bool can_castle_kingside(Color c) const;
165 bool can_castle_queenside(Color c) const;
166 bool can_castle(Color c) const;
167 Square initial_kr_square(Color c) const;
168 Square initial_qr_square(Color c) const;
170 // Bitboards for pinned pieces and discovered check candidates
171 Bitboard discovered_check_candidates(Color c) const;
172 Bitboard pinned_pieces(Color c) const;
174 // Checking pieces and under check information
175 Bitboard checkers() const;
176 bool is_check() const;
179 Square piece_list(Color c, PieceType pt, int index) const;
180 const Square* piece_list_begin(Color c, PieceType pt) const;
182 // Information about attacks to or from a given square
183 Bitboard attackers_to(Square s) const;
184 Bitboard attacks_from(Piece p, Square s) const;
185 static Bitboard attacks_from(Piece p, Square s, Bitboard occ);
186 template<PieceType> Bitboard attacks_from(Square s) const;
187 template<PieceType> Bitboard attacks_from(Square s, Color c) const;
189 // Properties of moves
190 bool pl_move_is_legal(Move m, Bitboard pinned) const;
191 bool pl_move_is_evasion(Move m, Bitboard pinned) const;
192 bool move_is_check(Move m) const;
193 bool move_is_check(Move m, const CheckInfo& ci) const;
194 bool move_is_capture(Move m) const;
195 bool move_is_capture_or_promotion(Move m) const;
196 bool move_is_passed_pawn_push(Move m) const;
197 bool move_attacks_square(Move m, Square s) const;
199 // Piece captured with previous moves
200 PieceType captured_piece_type() const;
202 // Information about pawns
203 bool pawn_is_passed(Color c, Square s) const;
206 bool square_is_weak(Square s, Color c) const;
208 // Doing and undoing moves
209 void do_setup_move(Move m);
210 void do_move(Move m, StateInfo& st);
211 void do_move(Move m, StateInfo& st, const CheckInfo& ci, bool moveIsCheck);
212 void undo_move(Move m);
213 void do_null_move(StateInfo& st);
214 void undo_null_move();
216 // Static exchange evaluation
217 int see(Square from, Square to) const;
218 int see(Move m) const;
219 int see_sign(Move m) const;
221 // Accessing hash keys
223 Key get_exclusion_key() const;
224 Key get_pawn_key() const;
225 Key get_material_key() const;
227 // Incremental evaluation
229 Value non_pawn_material(Color c) const;
230 static Score pst_delta(Piece piece, Square from, Square to);
232 // Game termination checks
233 bool is_mate() const;
234 bool is_draw() const;
236 // Check if side to move could be mated in one
237 bool has_mate_threat();
239 // Number of plies from starting position
240 int startpos_ply_counter() const;
242 // Other properties of the position
243 bool opposite_colored_bishops() const;
244 bool has_pawn_on_7th(Color c) const;
245 bool is_chess960() const;
247 // Current thread ID searching on the position
250 int64_t nodes_searched() const;
251 void set_nodes_searched(int64_t n);
253 // Position consistency check, for debugging
254 bool is_ok(int* failedStep = NULL) const;
256 // Static member functions
257 static void init_zobrist();
258 static void init_piece_square_tables();
262 // Initialization helper functions (used while setting up a position)
265 void put_piece(Piece p, Square s);
266 void do_allow_oo(Color c);
267 void do_allow_ooo(Color c);
268 bool set_castling_rights(char token);
270 // Helper functions for doing and undoing moves
271 void do_capture_move(Key& key, PieceType capture, Color them, Square to, bool ep);
272 void do_castle_move(Move m);
273 void undo_castle_move(Move m);
274 void find_checkers();
276 template<bool FindPinned>
277 Bitboard hidden_checkers(Color c) const;
279 // Computing hash keys from scratch (for initialization and debugging)
280 Key compute_key() const;
281 Key compute_pawn_key() const;
282 Key compute_material_key() const;
284 // Computing incremental evaluation scores and material counts
285 static Score pst(Color c, PieceType pt, Square s);
286 Score compute_value() const;
287 Value compute_non_pawn_material(Color c) const;
293 Bitboard byTypeBB[8], byColorBB[2];
296 int pieceCount[2][8]; // [color][pieceType]
299 Square pieceList[2][8][16]; // [color][pieceType][index]
300 int index[64]; // [square]
304 Key history[MaxGameLength];
305 int castleRightsMask[64];
306 StateInfo startState;
307 File initialKFile, initialKRFile, initialQRFile;
309 int startPosPlyCounter;
315 static Key zobrist[2][8][64];
316 static Key zobEp[64];
317 static Key zobCastle[16];
318 static Key zobSideToMove;
319 static Score PieceSquareTable[16][64];
320 static Key zobExclusion;
321 static const Value seeValues[8];
322 static const Value PieceValueMidgame[17];
323 static const Value PieceValueEndgame[17];
326 inline int64_t Position::nodes_searched() const {
330 inline void Position::set_nodes_searched(int64_t n) {
334 inline Piece Position::piece_on(Square s) const {
338 inline Color Position::color_of_piece_on(Square s) const {
339 return color_of_piece(piece_on(s));
342 inline PieceType Position::type_of_piece_on(Square s) const {
343 return type_of_piece(piece_on(s));
346 inline bool Position::square_is_empty(Square s) const {
347 return piece_on(s) == PIECE_NONE;
350 inline bool Position::square_is_occupied(Square s) const {
351 return !square_is_empty(s);
354 inline Value Position::midgame_value_of_piece_on(Square s) const {
355 return PieceValueMidgame[piece_on(s)];
358 inline Value Position::endgame_value_of_piece_on(Square s) const {
359 return PieceValueEndgame[piece_on(s)];
362 inline Color Position::side_to_move() const {
366 inline Bitboard Position::occupied_squares() const {
370 inline Bitboard Position::empty_squares() const {
371 return ~occupied_squares();
374 inline Bitboard Position::pieces_of_color(Color c) const {
378 inline Bitboard Position::pieces(PieceType pt) const {
382 inline Bitboard Position::pieces(PieceType pt, Color c) const {
383 return byTypeBB[pt] & byColorBB[c];
386 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2) const {
387 return byTypeBB[pt1] | byTypeBB[pt2];
390 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2, Color c) const {
391 return (byTypeBB[pt1] | byTypeBB[pt2]) & byColorBB[c];
394 inline int Position::piece_count(Color c, PieceType pt) const {
395 return pieceCount[c][pt];
398 inline Square Position::piece_list(Color c, PieceType pt, int idx) const {
399 return pieceList[c][pt][idx];
402 inline const Square* Position::piece_list_begin(Color c, PieceType pt) const {
403 return pieceList[c][pt];
406 inline Square Position::ep_square() const {
410 inline Square Position::king_square(Color c) const {
411 return pieceList[c][KING][0];
414 inline bool Position::can_castle_kingside(Color side) const {
415 return st->castleRights & (1+int(side));
418 inline bool Position::can_castle_queenside(Color side) const {
419 return st->castleRights & (4+4*int(side));
422 inline bool Position::can_castle(Color side) const {
423 return can_castle_kingside(side) || can_castle_queenside(side);
426 inline Square Position::initial_kr_square(Color c) const {
427 return relative_square(c, make_square(initialKRFile, RANK_1));
430 inline Square Position::initial_qr_square(Color c) const {
431 return relative_square(c, make_square(initialQRFile, RANK_1));
435 inline Bitboard Position::attacks_from<PAWN>(Square s, Color c) const {
436 return NonSlidingAttacksBB[make_piece(c, PAWN)][s];
439 template<PieceType Piece> // Knight and King and white pawns
440 inline Bitboard Position::attacks_from(Square s) const {
441 return NonSlidingAttacksBB[Piece][s];
445 inline Bitboard Position::attacks_from<BISHOP>(Square s) const {
446 return bishop_attacks_bb(s, occupied_squares());
450 inline Bitboard Position::attacks_from<ROOK>(Square s) const {
451 return rook_attacks_bb(s, occupied_squares());
455 inline Bitboard Position::attacks_from<QUEEN>(Square s) const {
456 return attacks_from<ROOK>(s) | attacks_from<BISHOP>(s);
459 inline Bitboard Position::checkers() const {
460 return st->checkersBB;
463 inline bool Position::is_check() const {
464 return st->checkersBB != EmptyBoardBB;
467 inline bool Position::pawn_is_passed(Color c, Square s) const {
468 return !(pieces(PAWN, opposite_color(c)) & passed_pawn_mask(c, s));
471 inline bool Position::square_is_weak(Square s, Color c) const {
472 return !(pieces(PAWN, opposite_color(c)) & attack_span_mask(c, s));
475 inline Key Position::get_key() const {
479 inline Key Position::get_exclusion_key() const {
480 return st->key ^ zobExclusion;
483 inline Key Position::get_pawn_key() const {
487 inline Key Position::get_material_key() const {
488 return st->materialKey;
491 inline Score Position::pst(Color c, PieceType pt, Square s) {
492 return PieceSquareTable[make_piece(c, pt)][s];
495 inline Score Position::pst_delta(Piece piece, Square from, Square to) {
496 return PieceSquareTable[piece][to] - PieceSquareTable[piece][from];
499 inline Score Position::value() const {
503 inline Value Position::non_pawn_material(Color c) const {
504 return st->npMaterial[c];
507 inline bool Position::move_is_passed_pawn_push(Move m) const {
509 Color c = side_to_move();
510 return piece_on(move_from(m)) == make_piece(c, PAWN)
511 && pawn_is_passed(c, move_to(m));
514 inline int Position::startpos_ply_counter() const {
515 return startPosPlyCounter;
518 inline bool Position::opposite_colored_bishops() const {
520 return piece_count(WHITE, BISHOP) == 1 && piece_count(BLACK, BISHOP) == 1
521 && opposite_color_squares(piece_list(WHITE, BISHOP, 0), piece_list(BLACK, BISHOP, 0));
524 inline bool Position::has_pawn_on_7th(Color c) const {
525 return pieces(PAWN, c) & rank_bb(relative_rank(c, RANK_7));
528 inline bool Position::is_chess960() const {
532 inline bool Position::move_is_capture(Move m) const {
534 // Move must not be MOVE_NONE !
535 return (m & (3 << 15)) ? !move_is_castle(m) : !square_is_empty(move_to(m));
538 inline bool Position::move_is_capture_or_promotion(Move m) const {
540 // Move must not be MOVE_NONE !
541 return (m & (0x1F << 12)) ? !move_is_castle(m) : !square_is_empty(move_to(m));
544 inline PieceType Position::captured_piece_type() const {
545 return st->capturedType;
548 inline int Position::thread() const {
552 inline void Position::do_allow_oo(Color c) {
553 st->castleRights |= (1 + int(c));
556 inline void Position::do_allow_ooo(Color c) {
557 st->castleRights |= (4 + 4*int(c));
560 #endif // !defined(POSITION_H_INCLUDED)