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 Marco Costalba
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 a silly and noisy warning from MSVC compiler
27 // Forcing value to bool 'true' or 'false' (performance warning)
28 #pragma warning(disable: 4800)
38 #include "direction.h"
49 /// FEN string for the initial position:
50 const std::string StartPosition =
51 "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1";
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 /// Castle rights, encoded as bit fields
81 /// The StateInfo struct stores information we need to restore a Position
82 /// object to its previous state when we retract a move. Whenever a move
83 /// is made on the board (by calling Position::do_move), an StateInfo object
84 /// must be passed as a parameter.
87 Key key, pawnKey, materialKey;
88 int castleRights, rule50;
90 Value mgValue, egValue;
99 /// The position data structure. A position consists of the following data:
101 /// * For each piece type, a bitboard representing the squares occupied
102 /// by pieces of that type.
103 /// * For each color, a bitboard representing the squares occupiecd by
104 /// pieces of that color.
105 /// * A bitboard of all occupied squares.
106 /// * A bitboard of all checking pieces.
107 /// * A 64-entry array of pieces, indexed by the squares of the board.
108 /// * The current side to move.
109 /// * Information about the castling rights for both sides.
110 /// * The initial files of the kings and both pairs of rooks. This is
111 /// used to implement the Chess960 castling rules.
112 /// * The en passant square (which is SQ_NONE if no en passant capture is
114 /// * The squares of the kings for both sides.
115 /// * The last move played.
116 /// * Hash keys for the position itself, the current pawn structure, and
117 /// the current material situation.
118 /// * Hash keys for all previous positions in the game (for detecting
119 /// repetition draws.
120 /// * A counter for detecting 50 move rule draws.
124 friend class MaterialInfo;
125 friend class EndgameFunctions;
130 Position(const Position& pos);
131 Position(const std::string& fen);
134 void from_fen(const std::string& fen);
135 const std::string to_fen() const;
136 void print(Move m = MOVE_NONE) const;
139 void copy(const Position &pos);
140 void flipped_copy(const Position &pos);
142 // The piece on a given square
143 Piece piece_on(Square s) const;
144 PieceType type_of_piece_on(Square s) const;
145 Color color_of_piece_on(Square s) const;
146 bool square_is_empty(Square s) const;
147 bool square_is_occupied(Square s) const;
148 Value midgame_value_of_piece_on(Square s) const;
149 Value endgame_value_of_piece_on(Square s) const;
152 Color side_to_move() const;
154 // Bitboard representation of the position
155 Bitboard empty_squares() const;
156 Bitboard occupied_squares() const;
157 Bitboard pieces_of_color(Color c) const;
158 Bitboard pieces_of_type(PieceType pt) const;
159 Bitboard pieces_of_color_and_type(Color c, PieceType pt) const;
160 Bitboard pawns() const;
161 Bitboard knights() const;
162 Bitboard bishops() const;
163 Bitboard rooks() const;
164 Bitboard queens() const;
165 Bitboard kings() const;
166 Bitboard rooks_and_queens() const;
167 Bitboard bishops_and_queens() const;
168 Bitboard sliders() const;
169 Bitboard pawns(Color c) const;
170 Bitboard knights(Color c) const;
171 Bitboard bishops(Color c) const;
172 Bitboard rooks(Color c) const;
173 Bitboard queens(Color c) const;
174 Bitboard kings(Color c) const;
175 Bitboard rooks_and_queens(Color c) const;
176 Bitboard bishops_and_queens(Color c) const;
177 Bitboard sliders_of_color(Color c) const;
179 // Number of pieces of each color and type
180 int piece_count(Color c, PieceType pt) const;
182 // The en passant square
183 Square ep_square() const;
185 // Current king position for each color
186 Square king_square(Color c) const;
189 bool can_castle_kingside(Color c) const;
190 bool can_castle_queenside(Color c) const;
191 bool can_castle(Color c) const;
192 Square initial_kr_square(Color c) const;
193 Square initial_qr_square(Color c) const;
196 Bitboard sliding_attacks(Square s, Direction d) const;
197 Bitboard ray_attacks(Square s, SignedDirection d) const;
198 Bitboard pawn_attacks(Color c, Square s) const;
201 Bitboard piece_attacks(Square s) const;
203 // Bitboards for pinned pieces and discovered check candidates
204 Bitboard discovered_check_candidates(Color c) const;
205 Bitboard pinned_pieces(Color c, Bitboard& p) const;
206 Bitboard pinned_pieces(Color c) const;
209 Bitboard checkers() const;
212 Square piece_list(Color c, PieceType pt, int index) const;
214 // Attack information for a given square
215 bool square_is_attacked(Square s, Color c) const;
216 Bitboard attacks_to(Square s) const;
217 Bitboard attacks_to(Square s, Color c) const;
218 bool is_check() const;
219 bool pawn_attacks_square(Color c, Square f, Square t) const;
222 Bitboard piece_attacks_square(Square f, Square t) const; // Dispatch at compile-time
224 bool piece_attacks_square(Piece p, Square f, Square t) const; // Dispatch at run-time
226 // Properties of moves
227 bool pl_move_is_legal(Move m) const;
228 bool pl_move_is_legal(Move m, Bitboard pinned) const;
229 bool move_is_check(Move m) const;
230 bool move_is_check(Move m, Bitboard dcCandidates) const;
231 bool move_is_capture(Move m) const;
232 bool move_is_deep_pawn_push(Move m) const;
233 bool move_is_pawn_push_to_7th(Move m) const;
234 bool move_is_passed_pawn_push(Move m) const;
235 bool move_was_passed_pawn_push(Move m) const;
236 bool move_attacks_square(Move m, Square s) const;
238 // Information about pawns
239 bool pawn_is_passed(Color c, Square s) const;
240 bool pawn_is_isolated(Color c, Square s) const;
241 bool pawn_is_doubled(Color c, Square s) const;
243 // Open and half-open files
244 bool file_is_open(File f) const;
245 bool file_is_half_open(Color c, File f) const;
248 bool square_is_weak(Square s, Color c) const;
250 // Doing and undoing moves
251 void setStartState(const StateInfo& st);
252 void do_move(Move m, StateInfo& st);
253 void do_move(Move m, StateInfo& st, Bitboard dcCandidates);
254 void undo_move(Move m);
255 void do_null_move(StateInfo& st);
256 void undo_null_move();
258 // Static exchange evaluation
259 int see(Square from, Square to) const;
260 int see(Move m) const;
261 int see(Square to) const;
263 // Accessing hash keys
265 Key get_pawn_key() const;
266 Key get_material_key() const;
268 // Incremental evaluation
269 Value mg_value() const;
270 Value eg_value() const;
271 Value non_pawn_material(Color c) const;
272 Phase game_phase() const;
273 Value mg_pst_delta(Move m) const;
275 // Game termination checks
276 bool is_mate() const;
277 bool is_draw() const;
279 // Check if one side threatens a mate in one
280 bool has_mate_threat(Color c);
282 // Number of plies since the last non-reversible move
283 int rule_50_counter() const;
285 // Other properties of the position
286 bool opposite_colored_bishops() const;
287 bool has_pawn_on_7th(Color c) const;
289 // Reset the gamePly variable to 0
290 void reset_game_ply();
292 // Position consistency check, for debugging
293 bool is_ok(int* failedStep = NULL) const;
295 // Static member functions:
296 static void init_zobrist();
297 static void init_piece_square_tables();
301 // Initialization helper functions (used while setting up a position)
303 void put_piece(Piece p, Square s);
304 void allow_oo(Color c);
305 void allow_ooo(Color c);
307 // Helper functions for doing and undoing moves
308 void do_capture_move(Move m, PieceType capture, Color them, Square to);
309 void do_castle_move(Move m);
310 void do_promotion_move(Move m);
311 void do_ep_move(Move m);
312 void undo_castle_move(Move m);
313 void undo_promotion_move(Move m);
314 void undo_ep_move(Move m);
315 void find_checkers();
317 template<PieceType Piece>
318 void update_checkers(Bitboard* pCheckersBB, Square ksq, Square from, Square to, Bitboard dcCandidates);
320 template<bool FindPinned>
321 Bitboard hidden_checkers(Color c) const;
323 // Computing hash keys from scratch (for initialization and debugging)
324 Key compute_key() const;
325 Key compute_pawn_key() const;
326 Key compute_material_key() const;
328 // Computing incremental evaluation scores and material counts
333 template<GamePhase> Value pst(Color c, PieceType pt, Square s) const;
334 template<GamePhase> Value compute_value() const;
335 Value compute_non_pawn_material(Color c) const;
338 Bitboard byColorBB[2], byTypeBB[8];
344 int pieceCount[2][8]; // [color][pieceType]
347 Square pieceList[2][8][16]; // [color][pieceType][index]
351 Square kingSquare[2];
354 Key history[MaxGameLength];
356 File initialKFile, initialKRFile, initialQRFile;
357 StateInfo startState;
361 static int castleRightsMask[64];
362 static Key zobrist[2][8][64];
363 static Key zobEp[64];
364 static Key zobCastle[16];
365 static Key zobMaterial[2][8][16];
366 static Key zobSideToMove;
367 static Value MgPieceSquareTable[16][64];
368 static Value EgPieceSquareTable[16][64];
373 //// Inline functions
376 inline Piece Position::piece_on(Square s) const {
380 inline Color Position::color_of_piece_on(Square s) const {
381 return color_of_piece(piece_on(s));
384 inline PieceType Position::type_of_piece_on(Square s) const {
385 return type_of_piece(piece_on(s));
388 inline bool Position::square_is_empty(Square s) const {
389 return piece_on(s) == EMPTY;
392 inline bool Position::square_is_occupied(Square s) const {
393 return !square_is_empty(s);
396 inline Value Position::midgame_value_of_piece_on(Square s) const {
397 return piece_value_midgame(piece_on(s));
400 inline Value Position::endgame_value_of_piece_on(Square s) const {
401 return piece_value_endgame(piece_on(s));
404 inline Color Position::side_to_move() const {
408 inline Bitboard Position::occupied_squares() const {
412 inline Bitboard Position::empty_squares() const {
413 return ~(occupied_squares());
416 inline Bitboard Position::pieces_of_color(Color c) const {
420 inline Bitboard Position::pieces_of_type(PieceType pt) const {
424 inline Bitboard Position::pieces_of_color_and_type(Color c, PieceType pt) const {
425 return pieces_of_color(c) & pieces_of_type(pt);
428 inline Bitboard Position::pawns() const {
429 return pieces_of_type(PAWN);
432 inline Bitboard Position::knights() const {
433 return pieces_of_type(KNIGHT);
436 inline Bitboard Position::bishops() const {
437 return pieces_of_type(BISHOP);
440 inline Bitboard Position::rooks() const {
441 return pieces_of_type(ROOK);
444 inline Bitboard Position::queens() const {
445 return pieces_of_type(QUEEN);
448 inline Bitboard Position::kings() const {
449 return pieces_of_type(KING);
452 inline Bitboard Position::rooks_and_queens() const {
453 return rooks() | queens();
456 inline Bitboard Position::bishops_and_queens() const {
457 return bishops() | queens();
460 inline Bitboard Position::sliders() const {
461 return bishops() | queens() | rooks();
464 inline Bitboard Position::pawns(Color c) const {
465 return pieces_of_color_and_type(c, PAWN);
468 inline Bitboard Position::knights(Color c) const {
469 return pieces_of_color_and_type(c, KNIGHT);
472 inline Bitboard Position::bishops(Color c) const {
473 return pieces_of_color_and_type(c, BISHOP);
476 inline Bitboard Position::rooks(Color c) const {
477 return pieces_of_color_and_type(c, ROOK);
480 inline Bitboard Position::queens(Color c) const {
481 return pieces_of_color_and_type(c, QUEEN);
484 inline Bitboard Position::kings(Color c) const {
485 return pieces_of_color_and_type(c, KING);
488 inline Bitboard Position::rooks_and_queens(Color c) const {
489 return rooks_and_queens() & pieces_of_color(c);
492 inline Bitboard Position::bishops_and_queens(Color c) const {
493 return bishops_and_queens() & pieces_of_color(c);
496 inline Bitboard Position::sliders_of_color(Color c) const {
497 return sliders() & pieces_of_color(c);
500 inline int Position::piece_count(Color c, PieceType pt) const {
501 return pieceCount[c][pt];
504 inline Square Position::piece_list(Color c, PieceType pt, int index) const {
505 return pieceList[c][pt][index];
508 inline Square Position::ep_square() const {
512 inline Square Position::king_square(Color c) const {
513 return kingSquare[c];
516 inline bool Position::can_castle_kingside(Color side) const {
517 return st->castleRights & (1+int(side));
520 inline bool Position::can_castle_queenside(Color side) const {
521 return st->castleRights & (4+4*int(side));
524 inline bool Position::can_castle(Color side) const {
525 return can_castle_kingside(side) || can_castle_queenside(side);
528 inline Square Position::initial_kr_square(Color c) const {
529 return relative_square(c, make_square(initialKRFile, RANK_1));
532 inline Square Position::initial_qr_square(Color c) const {
533 return relative_square(c, make_square(initialQRFile, RANK_1));
536 inline Bitboard Position::pawn_attacks(Color c, Square s) const {
537 return StepAttackBB[piece_of_color_and_type(c, PAWN)][s];
541 inline Bitboard Position::piece_attacks<PAWN>(Square s) const {
542 return StepAttackBB[piece_of_color_and_type(opposite_color(sideToMove), PAWN)][s];
546 inline Bitboard Position::piece_attacks<KNIGHT>(Square s) const {
547 return StepAttackBB[KNIGHT][s];
551 inline Bitboard Position::piece_attacks<BISHOP>(Square s) const {
552 return bishop_attacks_bb(s, occupied_squares());
556 inline Bitboard Position::piece_attacks<ROOK>(Square s) const {
557 return rook_attacks_bb(s, occupied_squares());
561 inline Bitboard Position::piece_attacks<QUEEN>(Square s) const {
562 return piece_attacks<ROOK>(s) | piece_attacks<BISHOP>(s);
566 inline Bitboard Position::piece_attacks<KING>(Square s) const {
567 return StepAttackBB[KING][s];
570 inline Bitboard Position::checkers() const {
571 return st->checkersBB;
574 inline bool Position::is_check() const {
575 return st->checkersBB != EmptyBoardBB;
578 inline bool Position::pawn_attacks_square(Color c, Square f, Square t) const {
579 return bit_is_set(pawn_attacks(c, f), t);
582 template<PieceType Piece>
583 Bitboard Position::piece_attacks_square(Square f, Square t) const {
584 return bit_is_set(piece_attacks<Piece>(f), t);
587 inline Bitboard Position::attacks_to(Square s, Color c) const {
589 return attacks_to(s) & pieces_of_color(c);
592 inline bool Position::square_is_attacked(Square s, Color c) const {
594 return attacks_to(s, c) != EmptyBoardBB;
597 inline bool Position::pawn_is_passed(Color c, Square s) const {
598 return !(pawns(opposite_color(c)) & passed_pawn_mask(c, s));
601 inline bool Position::pawn_is_isolated(Color c, Square s) const {
602 return !(pawns(c) & neighboring_files_bb(s));
605 inline bool Position::pawn_is_doubled(Color c, Square s) const {
606 return pawns(c) & squares_behind(c, s);
609 inline bool Position::file_is_open(File f) const {
610 return !(pawns() & file_bb(f));
613 inline bool Position::file_is_half_open(Color c, File f) const {
614 return !(pawns(c) & file_bb(f));
617 inline bool Position::square_is_weak(Square s, Color c) const {
618 return !(pawns(c) & outpost_mask(opposite_color(c), s));
621 inline Key Position::get_key() const {
625 inline Key Position::get_pawn_key() const {
629 inline Key Position::get_material_key() const {
630 return st->materialKey;
633 template<Position::GamePhase Phase>
634 inline Value Position::pst(Color c, PieceType pt, Square s) const {
635 return (Phase == MidGame ? MgPieceSquareTable[piece_of_color_and_type(c, pt)][s]
636 : EgPieceSquareTable[piece_of_color_and_type(c, pt)][s]);
639 inline Value Position::mg_pst_delta(Move m) const {
640 return MgPieceSquareTable[piece_on(move_from(m))][move_to(m)]
641 -MgPieceSquareTable[piece_on(move_from(m))][move_from(m)];
644 inline Value Position::mg_value() const {
648 inline Value Position::eg_value() const {
652 inline Value Position::non_pawn_material(Color c) const {
653 return npMaterial[c];
656 inline Phase Position::game_phase() const {
658 // Values modified by Joona Kiiski
659 static const Value MidgameLimit = Value(15713);
660 static const Value EndgameLimit = Value(4428);
662 Value npm = non_pawn_material(WHITE) + non_pawn_material(BLACK);
664 if (npm >= MidgameLimit)
665 return PHASE_MIDGAME;
666 else if(npm <= EndgameLimit)
667 return PHASE_ENDGAME;
669 return Phase(((npm - EndgameLimit) * 128) / (MidgameLimit - EndgameLimit));
672 inline bool Position::move_is_deep_pawn_push(Move m) const {
674 Color c = side_to_move();
675 return piece_on(move_from(m)) == piece_of_color_and_type(c, PAWN)
676 && relative_rank(c, move_to(m)) > RANK_4;
679 inline bool Position::move_is_pawn_push_to_7th(Move m) const {
681 Color c = side_to_move();
682 return piece_on(move_from(m)) == piece_of_color_and_type(c, PAWN)
683 && relative_rank(c, move_to(m)) == RANK_7;
686 inline bool Position::move_is_passed_pawn_push(Move m) const {
688 Color c = side_to_move();
689 return piece_on(move_from(m)) == piece_of_color_and_type(c, PAWN)
690 && pawn_is_passed(c, move_to(m));
693 inline bool Position::move_was_passed_pawn_push(Move m) const {
695 Color c = opposite_color(side_to_move());
696 return piece_on(move_to(m)) == piece_of_color_and_type(c, PAWN)
697 && pawn_is_passed(c, move_to(m));
700 inline int Position::rule_50_counter() const {
705 inline bool Position::opposite_colored_bishops() const {
707 return piece_count(WHITE, BISHOP) == 1
708 && piece_count(BLACK, BISHOP) == 1
709 && square_color(piece_list(WHITE, BISHOP, 0)) != square_color(piece_list(BLACK, BISHOP, 0));
712 inline bool Position::has_pawn_on_7th(Color c) const {
714 return pawns(c) & relative_rank_bb(c, RANK_7);
718 #endif // !defined(POSITION_H_INCLUDED)