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"
50 /// FEN string for the initial position:
51 const std::string StartPosition =
52 "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1";
54 /// Maximum number of plies per game (220 should be enough, because the
55 /// maximum search depth is 100, and during position setup we reset the
56 /// move counter for every non-reversible move):
57 const int MaxGameLength = 220;
64 /// Castle rights, encoded as bit fields:
76 /// The UndoInfo struct stores information we need to restore a Position
77 /// object to its previous state when we retract a move. Whenever a move
78 /// is made on the board (by calling Position::do_move), an UndoInfo object
79 /// must be passed as a parameter. When the move is unmade (by calling
80 /// Position::undo_move), the same UndoInfo object must be passed again.
86 Key key, pawnKey, materialKey;
90 Value mgValue, egValue;
94 /// The position data structure. A position consists of the following data:
96 /// * For each piece type, a bitboard representing the squares occupied
97 /// by pieces of that type.
98 /// * For each color, a bitboard representing the squares occupiecd by
99 /// pieces of that color.
100 /// * A bitboard of all occupied squares.
101 /// * A bitboard of all checking pieces.
102 /// * A 64-entry array of pieces, indexed by the squares of the board.
103 /// * The current side to move.
104 /// * Information about the castling rights for both sides.
105 /// * The initial files of the kings and both pairs of rooks. This is
106 /// used to implement the Chess960 castling rules.
107 /// * The en passant square (which is SQ_NONE if no en passant capture is
109 /// * The squares of the kings for both sides.
110 /// * The last move played.
111 /// * Hash keys for the position itself, the current pawn structure, and
112 /// the current material situation.
113 /// * Hash keys for all previous positions in the game (for detecting
114 /// repetition draws.
115 /// * A counter for detecting 50 move rule draws.
119 friend class MaterialInfo;
120 friend class EndgameFunctions;
125 Position(const Position& pos);
126 Position(const std::string& fen);
129 void from_fen(const std::string& fen);
130 const std::string to_fen() const;
131 void print(Move m = MOVE_NONE) const;
134 void copy(const Position &pos);
135 void flipped_copy(const Position &pos);
137 // The piece on a given square
138 Piece piece_on(Square s) const;
139 PieceType type_of_piece_on(Square s) const;
140 Color color_of_piece_on(Square s) const;
141 bool square_is_empty(Square s) const;
142 bool square_is_occupied(Square s) const;
143 Value midgame_value_of_piece_on(Square s) const;
144 Value endgame_value_of_piece_on(Square s) const;
147 Color side_to_move() const;
149 // Bitboard representation of the position
150 Bitboard empty_squares() const;
151 Bitboard occupied_squares() const;
152 Bitboard pieces_of_color(Color c) const;
153 Bitboard pieces_of_type(PieceType pt) const;
154 Bitboard pieces_of_color_and_type(Color c, PieceType pt) const;
155 Bitboard pawns() const;
156 Bitboard knights() const;
157 Bitboard bishops() const;
158 Bitboard rooks() const;
159 Bitboard queens() const;
160 Bitboard kings() const;
161 Bitboard rooks_and_queens() const;
162 Bitboard bishops_and_queens() const;
163 Bitboard sliders() const;
164 Bitboard pawns(Color c) const;
165 Bitboard knights(Color c) const;
166 Bitboard bishops(Color c) const;
167 Bitboard rooks(Color c) const;
168 Bitboard queens(Color c) const;
169 Bitboard kings(Color c) const;
170 Bitboard rooks_and_queens(Color c) const;
171 Bitboard bishops_and_queens(Color c) const;
172 Bitboard sliders_of_color(Color c) const;
174 // Number of pieces of each color and type
175 int piece_count(Color c, PieceType pt) const;
177 // The en passant square
178 Square ep_square() const;
180 // Current king position for each color
181 Square king_square(Color c) const;
184 bool can_castle_kingside(Color c) const;
185 bool can_castle_queenside(Color c) const;
186 bool can_castle(Color c) const;
187 Square initial_kr_square(Color c) const;
188 Square initial_qr_square(Color c) const;
191 Bitboard sliding_attacks(Square s, Direction d) const;
192 Bitboard ray_attacks(Square s, SignedDirection d) const;
193 Bitboard pawn_attacks(Color c, Square s) const;
196 Bitboard piece_attacks(Square s) 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;
203 Bitboard checkers() const;
206 Square piece_list(Color c, PieceType pt, int index) const;
208 // Attack information for a given square
209 bool square_is_attacked(Square s, Color c) const;
210 Bitboard attacks_to(Square s) const;
211 Bitboard attacks_to(Square s, Color c) const;
212 bool is_check() const;
213 bool pawn_attacks_square(Color c, Square f, Square t) const;
216 Bitboard piece_attacks_square(Square f, Square t) const; // Dispatch at compile-time
218 bool piece_attacks_square(Square f, Square t) const; // Dispatch at run-time
220 // Properties of moves
221 bool pl_move_is_legal(Move m) const;
222 bool pl_move_is_legal(Move m, Bitboard pinned) const;
223 bool move_is_check(Move m) const;
224 bool move_is_check(Move m, Bitboard dcCandidates) const;
225 bool move_is_capture(Move m) const;
226 bool move_is_deep_pawn_push(Move m) const;
227 bool move_is_pawn_push_to_7th(Move m) const;
228 bool move_is_passed_pawn_push(Move m) const;
229 bool move_was_passed_pawn_push(Move m) const;
230 bool move_attacks_square(Move m, Square s) const;
232 // Information about pawns
233 bool pawn_is_passed(Color c, Square s) const;
234 bool pawn_is_isolated(Color c, Square s) const;
235 bool pawn_is_doubled(Color c, Square s) const;
237 // Open and half-open files
238 bool file_is_open(File f) const;
239 bool file_is_half_open(Color c, File f) const;
242 bool square_is_weak(Square s, Color c) const;
244 // Doing and undoing moves
245 void backup(UndoInfo &u) const;
246 void restore(const UndoInfo &u);
247 void do_move(Move m, UndoInfo &u);
248 void do_move(Move m, UndoInfo &u, Bitboard dcCandidates);
249 void undo_move(Move m, const UndoInfo &u);
250 void do_null_move(UndoInfo &u);
251 void undo_null_move(const UndoInfo &u);
253 // Static exchange evaluation
254 int see(Square from, Square to) const;
255 int see(Move m) const;
256 int see(Square to) const;
258 // Accessing hash keys
260 Key get_pawn_key() const;
261 Key get_material_key() const;
263 // Incremental evaluation
264 Value mg_value() const;
265 Value eg_value() const;
266 Value non_pawn_material(Color c) const;
267 Phase game_phase() const;
268 Value mg_pst_delta(Move m) const;
270 // Game termination checks
271 bool is_mate() const;
272 bool is_draw() const;
274 // Check if one side threatens a mate in one
275 bool has_mate_threat(Color c);
277 // Number of plies since the last non-reversible move
278 int rule_50_counter() const;
280 // Other properties of the position
281 bool opposite_colored_bishops() const;
282 bool has_pawn_on_7th(Color c) const;
284 // Reset the gamePly variable to 0
285 void reset_game_ply();
287 // Position consistency check, for debugging
288 bool is_ok(int* failedStep = NULL) const;
290 // Static member functions:
291 static void init_zobrist();
292 static void init_piece_square_tables();
295 // Initialization helper functions (used while setting up a position)
297 void put_piece(Piece p, Square s);
298 void allow_oo(Color c);
299 void allow_ooo(Color c);
301 // Helper functions for doing and undoing moves
302 void do_capture_move(Move m, PieceType capture, Color them, Square to);
303 void do_castle_move(Move m);
304 void do_promotion_move(Move m, UndoInfo &u);
305 void do_ep_move(Move m);
306 void undo_castle_move(Move m);
307 void undo_promotion_move(Move m, const UndoInfo &u);
308 void undo_ep_move(Move m);
309 void find_checkers();
311 template<PieceType Piece, bool FindPinned>
312 Bitboard hidden_checks(Color c, Square ksq) const;
314 // Computing hash keys from scratch (for initialization and debugging)
315 Key compute_key() const;
316 Key compute_pawn_key() const;
317 Key compute_material_key() const;
319 // Computing incremental evaluation scores and material counts
320 Value mg_pst(Color c, PieceType pt, Square s) const;
321 Value eg_pst(Color c, PieceType pt, Square s) const;
322 Value compute_mg_value() const;
323 Value compute_eg_value() const;
324 Value compute_non_pawn_material(Color c) const;
327 Bitboard byColorBB[2], byTypeBB[8];
334 int pieceCount[2][8]; // [color][pieceType]
337 Square pieceList[2][8][16]; // [color][pieceType][index]
343 File initialKFile, initialKRFile, initialQRFile;
345 Square kingSquare[2];
347 Key key, pawnKey, materialKey, history[MaxGameLength];
349 Value mgValue, egValue;
353 static int castleRightsMask[64];
354 static Key zobrist[2][8][64];
355 static Key zobEp[64];
356 static Key zobCastle[16];
357 static Key zobMaterial[2][8][16];
358 static Key zobSideToMove;
359 static Value MgPieceSquareTable[16][64];
360 static Value EgPieceSquareTable[16][64];
365 //// Inline functions
368 inline Piece Position::piece_on(Square s) const {
372 inline Color Position::color_of_piece_on(Square s) const {
373 return color_of_piece(piece_on(s));
376 inline PieceType Position::type_of_piece_on(Square s) const {
377 return type_of_piece(piece_on(s));
380 inline bool Position::square_is_empty(Square s) const {
381 return piece_on(s) == EMPTY;
384 inline bool Position::square_is_occupied(Square s) const {
385 return !square_is_empty(s);
388 inline Value Position::midgame_value_of_piece_on(Square s) const {
389 return piece_value_midgame(piece_on(s));
392 inline Value Position::endgame_value_of_piece_on(Square s) const {
393 return piece_value_endgame(piece_on(s));
396 inline Color Position::side_to_move() const {
400 inline Bitboard Position::occupied_squares() const {
404 inline Bitboard Position::empty_squares() const {
405 return ~(occupied_squares());
408 inline Bitboard Position::pieces_of_color(Color c) const {
412 inline Bitboard Position::pieces_of_type(PieceType pt) const {
416 inline Bitboard Position::pieces_of_color_and_type(Color c, PieceType pt) const {
417 return pieces_of_color(c) & pieces_of_type(pt);
420 inline Bitboard Position::pawns() const {
421 return pieces_of_type(PAWN);
424 inline Bitboard Position::knights() const {
425 return pieces_of_type(KNIGHT);
428 inline Bitboard Position::bishops() const {
429 return pieces_of_type(BISHOP);
432 inline Bitboard Position::rooks() const {
433 return pieces_of_type(ROOK);
436 inline Bitboard Position::queens() const {
437 return pieces_of_type(QUEEN);
440 inline Bitboard Position::kings() const {
441 return pieces_of_type(KING);
444 inline Bitboard Position::rooks_and_queens() const {
445 return rooks() | queens();
448 inline Bitboard Position::bishops_and_queens() const {
449 return bishops() | queens();
452 inline Bitboard Position::sliders() const {
453 return bishops() | queens() | rooks();
456 inline Bitboard Position::pawns(Color c) const {
457 return pieces_of_color_and_type(c, PAWN);
460 inline Bitboard Position::knights(Color c) const {
461 return pieces_of_color_and_type(c, KNIGHT);
464 inline Bitboard Position::bishops(Color c) const {
465 return pieces_of_color_and_type(c, BISHOP);
468 inline Bitboard Position::rooks(Color c) const {
469 return pieces_of_color_and_type(c, ROOK);
472 inline Bitboard Position::queens(Color c) const {
473 return pieces_of_color_and_type(c, QUEEN);
476 inline Bitboard Position::kings(Color c) const {
477 return pieces_of_color_and_type(c, KING);
480 inline Bitboard Position::rooks_and_queens(Color c) const {
481 return rooks_and_queens() & pieces_of_color(c);
484 inline Bitboard Position::bishops_and_queens(Color c) const {
485 return bishops_and_queens() & pieces_of_color(c);
488 inline Bitboard Position::sliders_of_color(Color c) const {
489 return sliders() & pieces_of_color(c);
492 inline int Position::piece_count(Color c, PieceType pt) const {
493 return pieceCount[c][pt];
496 inline Square Position::piece_list(Color c, PieceType pt, int index) const {
497 return pieceList[c][pt][index];
500 inline Square Position::ep_square() const {
504 inline Square Position::king_square(Color c) const {
505 return kingSquare[c];
508 inline bool Position::can_castle_kingside(Color side) const {
509 return castleRights & (1+int(side));
512 inline bool Position::can_castle_queenside(Color side) const {
513 return castleRights & (4+4*int(side));
516 inline bool Position::can_castle(Color side) const {
517 return can_castle_kingside(side) || can_castle_queenside(side);
520 inline Square Position::initial_kr_square(Color c) const {
521 return relative_square(c, make_square(initialKRFile, RANK_1));
524 inline Square Position::initial_qr_square(Color c) const {
525 return relative_square(c, make_square(initialQRFile, RANK_1));
528 inline Bitboard Position::pawn_attacks(Color c, Square s) const {
529 return StepAttackBB[pawn_of_color(c)][s];
533 inline Bitboard Position::piece_attacks<KNIGHT>(Square s) const {
534 return StepAttackBB[KNIGHT][s];
538 inline Bitboard Position::piece_attacks<BISHOP>(Square s) const {
539 return bishop_attacks_bb(s, occupied_squares());
543 inline Bitboard Position::piece_attacks<ROOK>(Square s) const {
544 return rook_attacks_bb(s, occupied_squares());
548 inline Bitboard Position::piece_attacks<QUEEN>(Square s) const {
549 return piece_attacks<ROOK>(s) | piece_attacks<BISHOP>(s);
553 inline Bitboard Position::piece_attacks<KING>(Square s) const {
554 return StepAttackBB[KING][s];
557 inline Bitboard Position::checkers() const {
561 inline bool Position::is_check() const {
562 return checkersBB != EmptyBoardBB;
565 inline bool Position::pawn_attacks_square(Color c, Square f, Square t) const {
566 return bit_is_set(pawn_attacks(c, f), t);
569 template<PieceType Piece>
570 Bitboard Position::piece_attacks_square(Square f, Square t) const {
571 return bit_is_set(piece_attacks<Piece>(f), t);
574 inline bool Position::pawn_is_passed(Color c, Square s) const {
575 return !(pawns(opposite_color(c)) & passed_pawn_mask(c, s));
578 inline bool Position::pawn_is_isolated(Color c, Square s) const {
579 return !(pawns(c) & neighboring_files_bb(s));
582 inline bool Position::pawn_is_doubled(Color c, Square s) const {
583 return pawns(c) & squares_behind(c, s);
586 inline bool Position::file_is_open(File f) const {
587 return !(pawns() & file_bb(f));
590 inline bool Position::file_is_half_open(Color c, File f) const {
591 return !(pawns(c) & file_bb(f));
594 inline bool Position::square_is_weak(Square s, Color c) const {
595 return !(pawns(c) & outpost_mask(opposite_color(c), s));
598 inline Key Position::get_key() const {
602 inline Key Position::get_pawn_key() const {
606 inline Key Position::get_material_key() const {
610 inline Value Position::mg_pst(Color c, PieceType pt, Square s) const {
611 return MgPieceSquareTable[piece_of_color_and_type(c, pt)][s];
614 inline Value Position::mg_pst_delta(Move m) const {
615 return MgPieceSquareTable[piece_on(move_from(m))][move_to(m)]
616 -MgPieceSquareTable[piece_on(move_from(m))][move_from(m)];
619 inline Value Position::eg_pst(Color c, PieceType pt, Square s) const {
620 return EgPieceSquareTable[piece_of_color_and_type(c, pt)][s];
623 inline Value Position::mg_value() const {
627 inline Value Position::eg_value() const {
631 inline Value Position::non_pawn_material(Color c) const {
632 return npMaterial[c];
635 inline Phase Position::game_phase() const {
637 // The purpose of the Value(325) terms below is to make sure the difference
638 // between MidgameLimit and EndgameLimit is a power of 2, which should make
639 // the division at the end of the function a bit faster.
640 static const Value MidgameLimit = 2 * QueenValueMidgame
641 + 2 * RookValueMidgame
642 + 6 * BishopValueMidgame
645 static const Value EndgameLimit = 4 * RookValueMidgame - Value(325);
647 Value npm = non_pawn_material(WHITE) + non_pawn_material(BLACK);
649 if (npm >= MidgameLimit)
650 return PHASE_MIDGAME;
651 else if(npm <= EndgameLimit)
652 return PHASE_ENDGAME;
654 return Phase(((npm - EndgameLimit) * 128) / (MidgameLimit - EndgameLimit));
657 inline bool Position::move_is_deep_pawn_push(Move m) const {
659 Color c = side_to_move();
660 return piece_on(move_from(m)) == pawn_of_color(c)
661 && relative_rank(c, move_to(m)) > RANK_4;
664 inline bool Position::move_is_pawn_push_to_7th(Move m) const {
666 Color c = side_to_move();
667 return piece_on(move_from(m)) == pawn_of_color(c)
668 && relative_rank(c, move_to(m)) == RANK_7;
671 inline bool Position::move_is_passed_pawn_push(Move m) const {
673 Color c = side_to_move();
674 return piece_on(move_from(m)) == pawn_of_color(c)
675 && pawn_is_passed(c, move_to(m));
678 inline bool Position::move_was_passed_pawn_push(Move m) const {
680 Color c = opposite_color(side_to_move());
681 return piece_on(move_to(m)) == pawn_of_color(c)
682 && pawn_is_passed(c, move_to(m));
685 inline int Position::rule_50_counter() const {
690 inline bool Position::opposite_colored_bishops() const {
692 return piece_count(WHITE, BISHOP) == 1
693 && piece_count(BLACK, BISHOP) == 1
694 && square_color(piece_list(WHITE, BISHOP, 0)) != square_color(piece_list(BLACK, BISHOP, 0));
697 inline bool Position::has_pawn_on_7th(Color c) const {
699 return pawns(c) & relative_rank_bb(c, RANK_7);
703 #endif // !defined(POSITION_H_INCLUDED)