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 explicit Position(int threadID);
150 Position(const Position& pos, int threadID);
151 Position(const std::string& fen, int threadID);
154 void from_fen(const std::string& fen);
155 const std::string to_fen() const;
156 void print(Move m = MOVE_NONE) const;
159 void flipped_copy(const Position& pos);
161 // The piece on a given square
162 Piece piece_on(Square s) const;
163 PieceType type_of_piece_on(Square s) const;
164 Color color_of_piece_on(Square s) const;
165 bool square_is_empty(Square s) const;
166 bool square_is_occupied(Square s) const;
167 Value midgame_value_of_piece_on(Square s) const;
168 Value endgame_value_of_piece_on(Square s) const;
171 Color side_to_move() const;
173 // Bitboard representation of the position
174 Bitboard empty_squares() const;
175 Bitboard occupied_squares() const;
176 Bitboard pieces_of_color(Color c) const;
177 Bitboard pieces(PieceType pt) const;
178 Bitboard pieces(PieceType pt, Color c) const;
179 Bitboard pieces(PieceType pt1, PieceType pt2) const;
180 Bitboard pieces(PieceType pt1, PieceType pt2, Color c) const;
182 // Number of pieces of each color and type
183 int piece_count(Color c, PieceType pt) const;
185 // The en passant square
186 Square ep_square() const;
188 // Current king position for each color
189 Square king_square(Color c) const;
192 bool can_castle_kingside(Color c) const;
193 bool can_castle_queenside(Color c) const;
194 bool can_castle(Color c) const;
195 Square initial_kr_square(Color c) const;
196 Square initial_qr_square(Color c) const;
198 // Bitboards for pinned pieces and discovered check candidates
199 Bitboard discovered_check_candidates(Color c) const;
200 Bitboard pinned_pieces(Color c) const;
202 // Checking pieces and under check information
203 Bitboard checkers() const;
204 bool is_check() const;
207 Square piece_list(Color c, PieceType pt, int index) const;
208 const Square* piece_list_begin(Color c, PieceType pt) const;
210 // Information about attacks to or from a given square
211 Bitboard attackers_to(Square s) const;
212 Bitboard attacks_from(Piece p, Square s) const;
213 template<PieceType> Bitboard attacks_from(Square s) const;
214 template<PieceType> Bitboard attacks_from(Square s, Color c) const;
216 // Properties of moves
217 bool pl_move_is_legal(Move m, Bitboard pinned) const;
218 bool pl_move_is_evasion(Move m, Bitboard pinned) const;
219 bool move_is_check(Move m) const;
220 bool move_is_check(Move m, const CheckInfo& ci) const;
221 bool move_is_capture(Move m) const;
222 bool move_is_capture_or_promotion(Move m) const;
223 bool move_is_passed_pawn_push(Move m) const;
224 bool move_attacks_square(Move m, Square s) const;
226 // Piece captured with previous moves
227 PieceType captured_piece_type() const;
229 // Information about pawns
230 bool pawn_is_passed(Color c, Square s) const;
233 bool square_is_weak(Square s, Color c) const;
235 // Doing and undoing moves
237 void do_move(Move m, StateInfo& st);
238 void do_move(Move m, StateInfo& st, const CheckInfo& ci, bool moveIsCheck);
239 void undo_move(Move m);
240 void do_null_move(StateInfo& st);
241 void undo_null_move();
243 // Static exchange evaluation
244 int see(Square from, Square to) const;
245 int see(Move m) const;
246 int see(Square to) const;
247 int see_sign(Move m) const;
249 // Accessing hash keys
251 Key get_exclusion_key() const;
252 Key get_pawn_key() const;
253 Key get_material_key() const;
255 // Incremental evaluation
257 Value non_pawn_material(Color c) const;
258 static Score pst_delta(Piece piece, Square from, Square to);
260 // Game termination checks
261 bool is_mate() const;
262 bool is_draw() const;
264 // Check if side to move could be mated in one
265 bool has_mate_threat();
267 // Number of plies since the last non-reversible move
268 int rule_50_counter() const;
270 int startpos_ply_counter() const;
272 // Other properties of the position
273 bool opposite_colored_bishops() const;
274 bool has_pawn_on_7th(Color c) const;
276 // Current thread ID searching on the position
279 // Reset the gamePly variable to 0
280 void reset_game_ply();
282 void inc_startpos_ply_counter();
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;
338 int startPosPlyCounter;
343 static Key zobrist[2][8][64];
344 static Key zobEp[64];
345 static Key zobCastle[16];
346 static Key zobSideToMove;
347 static Score PieceSquareTable[16][64];
348 static Key zobExclusion;
353 //// Inline functions
356 inline Piece Position::piece_on(Square s) const {
360 inline Color Position::color_of_piece_on(Square s) const {
361 return color_of_piece(piece_on(s));
364 inline PieceType Position::type_of_piece_on(Square s) const {
365 return type_of_piece(piece_on(s));
368 inline bool Position::square_is_empty(Square s) const {
369 return piece_on(s) == PIECE_NONE;
372 inline bool Position::square_is_occupied(Square s) const {
373 return !square_is_empty(s);
376 inline Value Position::midgame_value_of_piece_on(Square s) const {
377 return PieceValueMidgame[piece_on(s)];
380 inline Value Position::endgame_value_of_piece_on(Square s) const {
381 return PieceValueEndgame[piece_on(s)];
384 inline Color Position::side_to_move() const {
388 inline Bitboard Position::occupied_squares() const {
392 inline Bitboard Position::empty_squares() const {
393 return ~(occupied_squares());
396 inline Bitboard Position::pieces_of_color(Color c) const {
400 inline Bitboard Position::pieces(PieceType pt) const {
404 inline Bitboard Position::pieces(PieceType pt, Color c) const {
405 return byTypeBB[pt] & byColorBB[c];
408 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2) const {
409 return byTypeBB[pt1] | byTypeBB[pt2];
412 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2, Color c) const {
413 return (byTypeBB[pt1] | byTypeBB[pt2]) & byColorBB[c];
416 inline int Position::piece_count(Color c, PieceType pt) const {
417 return pieceCount[c][pt];
420 inline Square Position::piece_list(Color c, PieceType pt, int idx) const {
421 return pieceList[c][pt][idx];
424 inline const Square* Position::piece_list_begin(Color c, PieceType pt) const {
425 return pieceList[c][pt];
428 inline Square Position::ep_square() const {
432 inline Square Position::king_square(Color c) const {
433 return pieceList[c][KING][0];
436 inline bool Position::can_castle_kingside(Color side) const {
437 return st->castleRights & (1+int(side));
440 inline bool Position::can_castle_queenside(Color side) const {
441 return st->castleRights & (4+4*int(side));
444 inline bool Position::can_castle(Color side) const {
445 return can_castle_kingside(side) || can_castle_queenside(side);
448 inline Square Position::initial_kr_square(Color c) const {
449 return relative_square(c, make_square(initialKRFile, RANK_1));
452 inline Square Position::initial_qr_square(Color c) const {
453 return relative_square(c, make_square(initialQRFile, RANK_1));
457 inline Bitboard Position::attacks_from<PAWN>(Square s, Color c) const {
458 return StepAttackBB[piece_of_color_and_type(c, PAWN)][s];
461 template<PieceType Piece> // Knight and King and white pawns
462 inline Bitboard Position::attacks_from(Square s) const {
463 return StepAttackBB[Piece][s];
467 inline Bitboard Position::attacks_from<BISHOP>(Square s) const {
468 return bishop_attacks_bb(s, occupied_squares());
472 inline Bitboard Position::attacks_from<ROOK>(Square s) const {
473 return rook_attacks_bb(s, occupied_squares());
477 inline Bitboard Position::attacks_from<QUEEN>(Square s) const {
478 return attacks_from<ROOK>(s) | attacks_from<BISHOP>(s);
481 inline Bitboard Position::checkers() const {
482 return st->checkersBB;
485 inline bool Position::is_check() const {
486 return st->checkersBB != EmptyBoardBB;
489 inline bool Position::pawn_is_passed(Color c, Square s) const {
490 return !(pieces(PAWN, opposite_color(c)) & passed_pawn_mask(c, s));
493 inline bool Position::square_is_weak(Square s, Color c) const {
494 return !(pieces(PAWN, opposite_color(c)) & attack_span_mask(c, s));
497 inline Key Position::get_key() const {
501 inline Key Position::get_exclusion_key() const {
502 return st->key ^ zobExclusion;
505 inline Key Position::get_pawn_key() const {
509 inline Key Position::get_material_key() const {
510 return st->materialKey;
513 inline Score Position::pst(Color c, PieceType pt, Square s) {
514 return PieceSquareTable[piece_of_color_and_type(c, pt)][s];
517 inline Score Position::pst_delta(Piece piece, Square from, Square to) {
518 return PieceSquareTable[piece][to] - PieceSquareTable[piece][from];
521 inline Score Position::value() const {
525 inline Value Position::non_pawn_material(Color c) const {
526 return st->npMaterial[c];
529 inline bool Position::move_is_passed_pawn_push(Move m) const {
531 Color c = side_to_move();
532 return piece_on(move_from(m)) == piece_of_color_and_type(c, PAWN)
533 && pawn_is_passed(c, move_to(m));
536 inline int Position::rule_50_counter() const {
541 inline int Position::startpos_ply_counter() const {
543 return startPosPlyCounter;
546 inline bool Position::opposite_colored_bishops() const {
548 return piece_count(WHITE, BISHOP) == 1
549 && piece_count(BLACK, BISHOP) == 1
550 && !same_color_squares(piece_list(WHITE, BISHOP, 0), piece_list(BLACK, BISHOP, 0));
553 inline bool Position::has_pawn_on_7th(Color c) const {
555 return pieces(PAWN, c) & relative_rank_bb(c, RANK_7);
558 inline bool Position::move_is_capture(Move m) const {
560 // Move must not be MOVE_NONE !
561 return (m & (3 << 15)) ? !move_is_castle(m) : !square_is_empty(move_to(m));
564 inline bool Position::move_is_capture_or_promotion(Move m) const {
566 // Move must not be MOVE_NONE !
567 return (m & (0x1F << 12)) ? !move_is_castle(m) : !square_is_empty(move_to(m));
570 inline PieceType Position::captured_piece_type() const {
571 return st->capturedType;
574 inline int Position::thread() const {
578 #endif // !defined(POSITION_H_INCLUDED)