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/>.
21 #if !defined(POSITION_H_INCLUDED)
22 #define POSITION_H_INCLUDED
24 // Disable some silly and noisy warning from MSVC compiler
27 // Forcing value to bool 'true' or 'false' (performance warning)
28 #pragma warning(disable: 4800)
30 // Conditional expression is constant
31 #pragma warning(disable: 4127)
42 #include "direction.h"
53 /// Maximum number of plies per game (220 should be enough, because the
54 /// maximum search depth is 100, and during position setup we reset the
55 /// move counter for every non-reversible move).
56 const int MaxGameLength = 220;
63 /// struct checkInfo is initialized at c'tor time and keeps
64 /// info used to detect if a move gives check.
68 explicit CheckInfo(const Position&);
70 Bitboard dcCandidates;
75 /// Castle rights, encoded as bit fields
93 /// The StateInfo struct stores information we need to restore a Position
94 /// object to its previous state when we retract a move. Whenever a move
95 /// is made on the board (by calling Position::do_move), an StateInfo object
96 /// must be passed as a parameter.
99 Key pawnKey, materialKey;
100 int castleRights, rule50, gamePly, pliesFromNull;
105 PieceType capturedType;
112 /// The position data structure. A position consists of the following data:
114 /// * For each piece type, a bitboard representing the squares occupied
115 /// by pieces of that type.
116 /// * For each color, a bitboard representing the squares occupied by
117 /// pieces of that color.
118 /// * A bitboard of all occupied squares.
119 /// * A bitboard of all checking pieces.
120 /// * A 64-entry array of pieces, indexed by the squares of the board.
121 /// * The current side to move.
122 /// * Information about the castling rights for both sides.
123 /// * The initial files of the kings and both pairs of rooks. This is
124 /// used to implement the Chess960 castling rules.
125 /// * The en passant square (which is SQ_NONE if no en passant capture is
127 /// * The squares of the kings for both sides.
128 /// * Hash keys for the position itself, the current pawn structure, and
129 /// the current material situation.
130 /// * Hash keys for all previous positions in the game for detecting
131 /// repetition draws.
132 /// * A counter for detecting 50 move rule draws.
136 friend class MaterialInfo;
137 friend class EndgameFunctions;
139 Position(); // No default or copy c'tor allowed
140 Position(const Position& pos);
149 Position(const Position& pos, int threadID);
150 Position(const std::string& fen, int threadID);
153 void from_fen(const std::string& fen);
154 const std::string to_fen() const;
155 void print(Move m = MOVE_NONE) const;
158 void flipped_copy(const Position& pos);
160 // The piece on a given square
161 Piece piece_on(Square s) const;
162 PieceType type_of_piece_on(Square s) const;
163 Color color_of_piece_on(Square s) const;
164 bool square_is_empty(Square s) const;
165 bool square_is_occupied(Square s) const;
166 Value midgame_value_of_piece_on(Square s) const;
167 Value endgame_value_of_piece_on(Square s) const;
170 Color side_to_move() const;
172 // Bitboard representation of the position
173 Bitboard empty_squares() const;
174 Bitboard occupied_squares() const;
175 Bitboard pieces_of_color(Color c) const;
176 Bitboard pieces(PieceType pt) const;
177 Bitboard pieces(PieceType pt, Color c) const;
178 Bitboard pieces(PieceType pt1, PieceType pt2) const;
179 Bitboard pieces(PieceType pt1, PieceType pt2, Color c) const;
181 // Number of pieces of each color and type
182 int piece_count(Color c, PieceType pt) const;
184 // The en passant square
185 Square ep_square() const;
187 // Current king position for each color
188 Square king_square(Color c) const;
191 bool can_castle_kingside(Color c) const;
192 bool can_castle_queenside(Color c) const;
193 bool can_castle(Color c) const;
194 Square initial_kr_square(Color c) const;
195 Square initial_qr_square(Color c) const;
197 // Bitboards for pinned pieces and discovered check candidates
198 Bitboard discovered_check_candidates(Color c) const;
199 Bitboard pinned_pieces(Color c) const;
201 // Checking pieces and under check information
202 Bitboard checkers() const;
203 bool is_check() const;
206 Square piece_list(Color c, PieceType pt, int index) const;
207 const Square* piece_list_begin(Color c, PieceType pt) const;
209 // Information about attacks to or from a given square
210 Bitboard attackers_to(Square s) const;
211 Bitboard attacks_from(Piece p, Square s) const;
212 template<PieceType> Bitboard attacks_from(Square s) const;
213 template<PieceType> Bitboard attacks_from(Square s, Color c) const;
215 // Properties of moves
216 bool pl_move_is_legal(Move m, Bitboard pinned) const;
217 bool pl_move_is_evasion(Move m, Bitboard pinned) const;
218 bool move_is_check(Move m) const;
219 bool move_is_check(Move m, const CheckInfo& ci) const;
220 bool move_is_capture(Move m) const;
221 bool move_is_capture_or_promotion(Move m) const;
222 bool move_is_passed_pawn_push(Move m) const;
223 bool move_attacks_square(Move m, Square s) const;
225 // Piece captured with previous moves
226 PieceType captured_piece_type() const;
228 // Information about pawns
229 bool pawn_is_passed(Color c, Square s) const;
232 bool square_is_weak(Square s, Color c) const;
234 // Doing and undoing moves
236 void do_move(Move m, StateInfo& st);
237 void do_move(Move m, StateInfo& st, const CheckInfo& ci, bool moveIsCheck);
238 void undo_move(Move m);
239 void do_null_move(StateInfo& st);
240 void undo_null_move();
242 // Static exchange evaluation
243 int see(Square from, Square to) const;
244 int see(Move m) const;
245 int see_sign(Move m) const;
247 // Accessing hash keys
249 Key get_exclusion_key() const;
250 Key get_pawn_key() const;
251 Key get_material_key() const;
253 // Incremental evaluation
255 Value non_pawn_material(Color c) const;
256 static Score pst_delta(Piece piece, Square from, Square to);
258 // Game termination checks
259 bool is_mate() const;
260 bool is_draw() const;
262 // Check if side to move could be mated in one
263 bool has_mate_threat();
265 // Number of plies since the last non-reversible move
266 int rule_50_counter() const;
268 int startpos_ply_counter() const;
270 // Other properties of the position
271 bool opposite_colored_bishops() const;
272 bool has_pawn_on_7th(Color c) const;
273 bool is_chess960() const;
275 // Current thread ID searching on the position
278 // Reset the gamePly variable to 0
279 void reset_game_ply();
280 void inc_startpos_ply_counter();
281 int64_t nodes_searched() const;
282 void set_nodes_searched(int64_t n);
284 // Position consistency check, for debugging
285 bool is_ok(int* failedStep = NULL) const;
287 // Static member functions
288 static void init_zobrist();
289 static void init_piece_square_tables();
293 // Initialization helper functions (used while setting up a position)
295 void put_piece(Piece p, Square s);
296 void allow_oo(Color c);
297 void allow_ooo(Color c);
298 bool set_castling_rights(char token);
300 // Helper functions for doing and undoing moves
301 void do_capture_move(Key& key, PieceType capture, Color them, Square to, bool ep);
302 void do_castle_move(Move m);
303 void undo_castle_move(Move m);
304 void find_checkers();
306 template<bool FindPinned>
307 Bitboard hidden_checkers(Color c) const;
309 // Computing hash keys from scratch (for initialization and debugging)
310 Key compute_key() const;
311 Key compute_pawn_key() const;
312 Key compute_material_key() const;
314 // Computing incremental evaluation scores and material counts
315 static Score pst(Color c, PieceType pt, Square s);
316 Score compute_value() const;
317 Value compute_non_pawn_material(Color c) const;
323 Bitboard byTypeBB[8], byColorBB[2];
326 int pieceCount[2][8]; // [color][pieceType]
329 Square pieceList[2][8][16]; // [color][pieceType][index]
330 int index[64]; // [square]
334 Key history[MaxGameLength];
335 int castleRightsMask[64];
336 StateInfo startState;
337 File initialKFile, initialKRFile, initialQRFile;
339 int startPosPlyCounter;
345 static Key zobrist[2][8][64];
346 static Key zobEp[64];
347 static Key zobCastle[16];
348 static Key zobSideToMove;
349 static Score PieceSquareTable[16][64];
350 static Key zobExclusion;
351 static const Value seeValues[8];
356 //// Inline functions
359 inline int64_t Position::nodes_searched() const {
363 inline void Position::set_nodes_searched(int64_t n) {
367 inline Piece Position::piece_on(Square s) const {
371 inline Color Position::color_of_piece_on(Square s) const {
372 return color_of_piece(piece_on(s));
375 inline PieceType Position::type_of_piece_on(Square s) const {
376 return type_of_piece(piece_on(s));
379 inline bool Position::square_is_empty(Square s) const {
380 return piece_on(s) == PIECE_NONE;
383 inline bool Position::square_is_occupied(Square s) const {
384 return !square_is_empty(s);
387 inline Value Position::midgame_value_of_piece_on(Square s) const {
388 return PieceValueMidgame[piece_on(s)];
391 inline Value Position::endgame_value_of_piece_on(Square s) const {
392 return PieceValueEndgame[piece_on(s)];
395 inline Color Position::side_to_move() const {
399 inline Bitboard Position::occupied_squares() const {
403 inline Bitboard Position::empty_squares() const {
404 return ~(occupied_squares());
407 inline Bitboard Position::pieces_of_color(Color c) const {
411 inline Bitboard Position::pieces(PieceType pt) const {
415 inline Bitboard Position::pieces(PieceType pt, Color c) const {
416 return byTypeBB[pt] & byColorBB[c];
419 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2) const {
420 return byTypeBB[pt1] | byTypeBB[pt2];
423 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2, Color c) const {
424 return (byTypeBB[pt1] | byTypeBB[pt2]) & byColorBB[c];
427 inline int Position::piece_count(Color c, PieceType pt) const {
428 return pieceCount[c][pt];
431 inline Square Position::piece_list(Color c, PieceType pt, int idx) const {
432 return pieceList[c][pt][idx];
435 inline const Square* Position::piece_list_begin(Color c, PieceType pt) const {
436 return pieceList[c][pt];
439 inline Square Position::ep_square() const {
443 inline Square Position::king_square(Color c) const {
444 return pieceList[c][KING][0];
447 inline bool Position::can_castle_kingside(Color side) const {
448 return st->castleRights & (1+int(side));
451 inline bool Position::can_castle_queenside(Color side) const {
452 return st->castleRights & (4+4*int(side));
455 inline bool Position::can_castle(Color side) const {
456 return can_castle_kingside(side) || can_castle_queenside(side);
459 inline Square Position::initial_kr_square(Color c) const {
460 return relative_square(c, make_square(initialKRFile, RANK_1));
463 inline Square Position::initial_qr_square(Color c) const {
464 return relative_square(c, make_square(initialQRFile, RANK_1));
468 inline Bitboard Position::attacks_from<PAWN>(Square s, Color c) const {
469 return StepAttackBB[piece_of_color_and_type(c, PAWN)][s];
472 template<PieceType Piece> // Knight and King and white pawns
473 inline Bitboard Position::attacks_from(Square s) const {
474 return StepAttackBB[Piece][s];
478 inline Bitboard Position::attacks_from<BISHOP>(Square s) const {
479 return bishop_attacks_bb(s, occupied_squares());
483 inline Bitboard Position::attacks_from<ROOK>(Square s) const {
484 return rook_attacks_bb(s, occupied_squares());
488 inline Bitboard Position::attacks_from<QUEEN>(Square s) const {
489 return attacks_from<ROOK>(s) | attacks_from<BISHOP>(s);
492 inline Bitboard Position::checkers() const {
493 return st->checkersBB;
496 inline bool Position::is_check() const {
497 return st->checkersBB != EmptyBoardBB;
500 inline bool Position::pawn_is_passed(Color c, Square s) const {
501 return !(pieces(PAWN, opposite_color(c)) & passed_pawn_mask(c, s));
504 inline bool Position::square_is_weak(Square s, Color c) const {
505 return !(pieces(PAWN, opposite_color(c)) & attack_span_mask(c, s));
508 inline Key Position::get_key() const {
512 inline Key Position::get_exclusion_key() const {
513 return st->key ^ zobExclusion;
516 inline Key Position::get_pawn_key() const {
520 inline Key Position::get_material_key() const {
521 return st->materialKey;
524 inline Score Position::pst(Color c, PieceType pt, Square s) {
525 return PieceSquareTable[piece_of_color_and_type(c, pt)][s];
528 inline Score Position::pst_delta(Piece piece, Square from, Square to) {
529 return PieceSquareTable[piece][to] - PieceSquareTable[piece][from];
532 inline Score Position::value() const {
536 inline Value Position::non_pawn_material(Color c) const {
537 return st->npMaterial[c];
540 inline bool Position::move_is_passed_pawn_push(Move m) const {
542 Color c = side_to_move();
543 return piece_on(move_from(m)) == piece_of_color_and_type(c, PAWN)
544 && pawn_is_passed(c, move_to(m));
547 inline int Position::rule_50_counter() const {
552 inline int Position::startpos_ply_counter() const {
554 return startPosPlyCounter;
557 inline bool Position::opposite_colored_bishops() const {
559 return piece_count(WHITE, BISHOP) == 1
560 && piece_count(BLACK, BISHOP) == 1
561 && !same_color_squares(piece_list(WHITE, BISHOP, 0), piece_list(BLACK, BISHOP, 0));
564 inline bool Position::has_pawn_on_7th(Color c) const {
566 return pieces(PAWN, c) & relative_rank_bb(c, RANK_7);
569 inline bool Position::is_chess960() const {
574 inline bool Position::move_is_capture(Move m) const {
576 // Move must not be MOVE_NONE !
577 return (m & (3 << 15)) ? !move_is_castle(m) : !square_is_empty(move_to(m));
580 inline bool Position::move_is_capture_or_promotion(Move m) const {
582 // Move must not be MOVE_NONE !
583 return (m & (0x1F << 12)) ? !move_is_castle(m) : !square_is_empty(move_to(m));
586 inline PieceType Position::captured_piece_type() const {
587 return st->capturedType;
590 inline int Position::thread() const {
594 #endif // !defined(POSITION_H_INCLUDED)