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 /// FEN string for the initial position
54 const std::string StartPosition = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1";
56 /// Maximum number of plies per game (220 should be enough, because the
57 /// maximum search depth is 100, and during position setup we reset the
58 /// move counter for every non-reversible move).
59 const int MaxGameLength = 220;
66 /// struct checkInfo is initialized at c'tor time and keeps
67 /// info used to detect if a move gives check.
71 CheckInfo(const Position&);
73 Bitboard dcCandidates;
78 /// Castle rights, encoded as bit fields
96 /// The StateInfo struct stores information we need to restore a Position
97 /// object to its previous state when we retract a move. Whenever a move
98 /// is made on the board (by calling Position::do_move), an StateInfo object
99 /// must be passed as a parameter.
102 Key pawnKey, materialKey;
103 int castleRights, rule50, pliesFromNull;
115 /// The position data structure. A position consists of the following data:
117 /// * For each piece type, a bitboard representing the squares occupied
118 /// by pieces of that type.
119 /// * For each color, a bitboard representing the squares occupied by
120 /// pieces of that color.
121 /// * A bitboard of all occupied squares.
122 /// * A bitboard of all checking pieces.
123 /// * A 64-entry array of pieces, indexed by the squares of the board.
124 /// * The current side to move.
125 /// * Information about the castling rights for both sides.
126 /// * The initial files of the kings and both pairs of rooks. This is
127 /// used to implement the Chess960 castling rules.
128 /// * The en passant square (which is SQ_NONE if no en passant capture is
130 /// * The squares of the kings for both sides.
131 /// * Hash keys for the position itself, the current pawn structure, and
132 /// the current material situation.
133 /// * Hash keys for all previous positions in the game for detecting
134 /// repetition draws.
135 /// * A counter for detecting 50 move rule draws.
139 friend class MaterialInfo;
140 friend class EndgameFunctions;
150 explicit Position(const Position& pos);
151 explicit Position(const std::string& fen);
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() 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 Score pst_delta(Piece piece, Square from, Square to) const;
260 // Game termination checks
261 bool is_mate() const;
262 bool is_draw() const;
264 // Check if one side threatens a mate in one
265 bool has_mate_threat(Color c);
267 // Number of plies since the last non-reversible move
268 int rule_50_counter() const;
270 // Other properties of the position
271 bool opposite_colored_bishops() const;
272 bool has_pawn_on_7th(Color c) const;
274 // Reset the gamePly variable to 0
275 void reset_game_ply();
277 // Position consistency check, for debugging
278 bool is_ok(int* failedStep = NULL) const;
280 // Static member functions
281 static void init_zobrist();
282 static void init_piece_square_tables();
286 // Initialization helper functions (used while setting up a position)
288 void put_piece(Piece p, Square s);
289 void allow_oo(Color c);
290 void allow_ooo(Color c);
292 // Helper functions for doing and undoing moves
293 void do_capture_move(Key& key, PieceType capture, Color them, Square to, bool ep);
294 void do_castle_move(Move m);
295 void undo_castle_move(Move m);
296 void find_checkers();
298 template<bool FindPinned>
299 Bitboard hidden_checkers(Color c) const;
301 // Computing hash keys from scratch (for initialization and debugging)
302 Key compute_key() const;
303 Key compute_pawn_key() const;
304 Key compute_material_key() const;
306 // Computing incremental evaluation scores and material counts
307 Score pst(Color c, PieceType pt, Square s) const;
308 Score compute_value() const;
309 Value compute_non_pawn_material(Color c) const;
315 Bitboard byTypeBB[8], byColorBB[2];
318 int pieceCount[2][8]; // [color][pieceType]
321 Square pieceList[2][8][16]; // [color][pieceType][index]
322 int index[64]; // [square]
327 Key history[MaxGameLength];
328 int castleRightsMask[64];
329 StateInfo startState;
330 File initialKFile, initialKRFile, initialQRFile;
334 static Key zobrist[2][8][64];
335 static Key zobEp[64];
336 static Key zobCastle[16];
337 static Key zobSideToMove;
338 static Score PieceSquareTable[16][64];
339 static Key zobExclusion;
344 //// Inline functions
347 inline Piece Position::piece_on(Square s) const {
351 inline Color Position::color_of_piece_on(Square s) const {
352 return color_of_piece(piece_on(s));
355 inline PieceType Position::type_of_piece_on(Square s) const {
356 return type_of_piece(piece_on(s));
359 inline bool Position::square_is_empty(Square s) const {
360 return piece_on(s) == EMPTY;
363 inline bool Position::square_is_occupied(Square s) const {
364 return !square_is_empty(s);
367 inline Value Position::midgame_value_of_piece_on(Square s) const {
368 return piece_value_midgame(piece_on(s));
371 inline Value Position::endgame_value_of_piece_on(Square s) const {
372 return piece_value_endgame(piece_on(s));
375 inline Color Position::side_to_move() const {
379 inline Bitboard Position::occupied_squares() const {
383 inline Bitboard Position::empty_squares() const {
384 return ~(occupied_squares());
387 inline Bitboard Position::pieces_of_color(Color c) const {
391 inline Bitboard Position::pieces(PieceType pt) const {
395 inline Bitboard Position::pieces(PieceType pt, Color c) const {
396 return byTypeBB[pt] & byColorBB[c];
399 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2) const {
400 return byTypeBB[pt1] | byTypeBB[pt2];
403 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2, Color c) const {
404 return (byTypeBB[pt1] | byTypeBB[pt2]) & byColorBB[c];
407 inline int Position::piece_count(Color c, PieceType pt) const {
408 return pieceCount[c][pt];
411 inline Square Position::piece_list(Color c, PieceType pt, int idx) const {
412 return pieceList[c][pt][idx];
415 inline const Square* Position::piece_list_begin(Color c, PieceType pt) const {
416 return pieceList[c][pt];
419 inline Square Position::ep_square() const {
423 inline Square Position::king_square(Color c) const {
424 return pieceList[c][KING][0];
427 inline bool Position::can_castle_kingside(Color side) const {
428 return st->castleRights & (1+int(side));
431 inline bool Position::can_castle_queenside(Color side) const {
432 return st->castleRights & (4+4*int(side));
435 inline bool Position::can_castle(Color side) const {
436 return can_castle_kingside(side) || can_castle_queenside(side);
439 inline Square Position::initial_kr_square(Color c) const {
440 return relative_square(c, make_square(initialKRFile, RANK_1));
443 inline Square Position::initial_qr_square(Color c) const {
444 return relative_square(c, make_square(initialQRFile, RANK_1));
448 inline Bitboard Position::attacks_from<PAWN>(Square s, Color c) const {
449 return StepAttackBB[piece_of_color_and_type(c, PAWN)][s];
452 template<PieceType Piece> // Knight and King and white pawns
453 inline Bitboard Position::attacks_from(Square s) const {
454 return StepAttackBB[Piece][s];
458 inline Bitboard Position::attacks_from<BISHOP>(Square s) const {
459 return bishop_attacks_bb(s, occupied_squares());
463 inline Bitboard Position::attacks_from<ROOK>(Square s) const {
464 return rook_attacks_bb(s, occupied_squares());
468 inline Bitboard Position::attacks_from<QUEEN>(Square s) const {
469 return attacks_from<ROOK>(s) | attacks_from<BISHOP>(s);
472 inline Bitboard Position::checkers() const {
473 return st->checkersBB;
476 inline bool Position::is_check() const {
477 return st->checkersBB != EmptyBoardBB;
480 inline bool Position::pawn_is_passed(Color c, Square s) const {
481 return !(pieces(PAWN, opposite_color(c)) & passed_pawn_mask(c, s));
484 inline bool Position::square_is_weak(Square s, Color c) const {
485 return !(pieces(PAWN, opposite_color(c)) & attack_span_mask(c, s));
488 inline Key Position::get_key() const {
492 inline Key Position::get_exclusion_key() const {
493 return st->key ^ zobExclusion;
496 inline Key Position::get_pawn_key() const {
500 inline Key Position::get_material_key() const {
501 return st->materialKey;
504 inline Score Position::pst(Color c, PieceType pt, Square s) const {
505 return PieceSquareTable[piece_of_color_and_type(c, pt)][s];
508 inline Score Position::pst_delta(Piece piece, Square from, Square to) const {
509 return PieceSquareTable[piece][to] - PieceSquareTable[piece][from];
512 inline Score Position::value() const {
516 inline Value Position::non_pawn_material(Color c) const {
517 return st->npMaterial[c];
520 inline bool Position::move_is_passed_pawn_push(Move m) const {
522 Color c = side_to_move();
523 return piece_on(move_from(m)) == piece_of_color_and_type(c, PAWN)
524 && pawn_is_passed(c, move_to(m));
527 inline int Position::rule_50_counter() const {
532 inline bool Position::opposite_colored_bishops() const {
534 return piece_count(WHITE, BISHOP) == 1
535 && piece_count(BLACK, BISHOP) == 1
536 && square_color(piece_list(WHITE, BISHOP, 0)) != square_color(piece_list(BLACK, BISHOP, 0));
539 inline bool Position::has_pawn_on_7th(Color c) const {
541 return pieces(PAWN, c) & relative_rank_bb(c, RANK_7);
544 inline bool Position::move_is_capture(Move m) const {
546 // Move must not be MOVE_NONE !
547 return (m & (3 << 15)) ? !move_is_castle(m) : !square_is_empty(move_to(m));
550 inline bool Position::move_is_capture_or_promotion(Move m) const {
552 // Move must not be MOVE_NONE !
553 return (m & (0x1F << 12)) ? !move_is_castle(m) : !square_is_empty(move_to(m));
556 inline PieceType Position::captured_piece() const {
560 #endif // !defined(POSITION_H_INCLUDED)