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;
89 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(Piece p, 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>
312 void update_checkers(Bitboard* pCheckersBB, Square ksq, Square from, Square to, Bitboard dcCandidates);
314 template<PieceType Piece, bool FindPinned>
315 Bitboard hidden_checks(Color c, Square ksq) const;
317 // Computing hash keys from scratch (for initialization and debugging)
318 Key compute_key() const;
319 Key compute_pawn_key() const;
320 Key compute_material_key() const;
322 // Computing incremental evaluation scores and material counts
323 Value mg_pst(Color c, PieceType pt, Square s) const;
324 Value eg_pst(Color c, PieceType pt, Square s) const;
325 Value compute_mg_value() const;
326 Value compute_eg_value() const;
327 Value compute_non_pawn_material(Color c) const;
330 Bitboard byColorBB[2], byTypeBB[8];
337 int pieceCount[2][8]; // [color][pieceType]
340 Square pieceList[2][8][16]; // [color][pieceType][index]
346 File initialKFile, initialKRFile, initialQRFile;
348 Square kingSquare[2];
350 Key key, pawnKey, materialKey, history[MaxGameLength];
352 Value mgValue, egValue;
356 static int castleRightsMask[64];
357 static Key zobrist[2][8][64];
358 static Key zobEp[64];
359 static Key zobCastle[16];
360 static Key zobMaterial[2][8][16];
361 static Key zobSideToMove;
362 static Value MgPieceSquareTable[16][64];
363 static Value EgPieceSquareTable[16][64];
368 //// Inline functions
371 inline Piece Position::piece_on(Square s) const {
375 inline Color Position::color_of_piece_on(Square s) const {
376 return color_of_piece(piece_on(s));
379 inline PieceType Position::type_of_piece_on(Square s) const {
380 return type_of_piece(piece_on(s));
383 inline bool Position::square_is_empty(Square s) const {
384 return piece_on(s) == EMPTY;
387 inline bool Position::square_is_occupied(Square s) const {
388 return !square_is_empty(s);
391 inline Value Position::midgame_value_of_piece_on(Square s) const {
392 return piece_value_midgame(piece_on(s));
395 inline Value Position::endgame_value_of_piece_on(Square s) const {
396 return piece_value_endgame(piece_on(s));
399 inline Color Position::side_to_move() const {
403 inline Bitboard Position::occupied_squares() const {
407 inline Bitboard Position::empty_squares() const {
408 return ~(occupied_squares());
411 inline Bitboard Position::pieces_of_color(Color c) const {
415 inline Bitboard Position::pieces_of_type(PieceType pt) const {
419 inline Bitboard Position::pieces_of_color_and_type(Color c, PieceType pt) const {
420 return pieces_of_color(c) & pieces_of_type(pt);
423 inline Bitboard Position::pawns() const {
424 return pieces_of_type(PAWN);
427 inline Bitboard Position::knights() const {
428 return pieces_of_type(KNIGHT);
431 inline Bitboard Position::bishops() const {
432 return pieces_of_type(BISHOP);
435 inline Bitboard Position::rooks() const {
436 return pieces_of_type(ROOK);
439 inline Bitboard Position::queens() const {
440 return pieces_of_type(QUEEN);
443 inline Bitboard Position::kings() const {
444 return pieces_of_type(KING);
447 inline Bitboard Position::rooks_and_queens() const {
448 return rooks() | queens();
451 inline Bitboard Position::bishops_and_queens() const {
452 return bishops() | queens();
455 inline Bitboard Position::sliders() const {
456 return bishops() | queens() | rooks();
459 inline Bitboard Position::pawns(Color c) const {
460 return pieces_of_color_and_type(c, PAWN);
463 inline Bitboard Position::knights(Color c) const {
464 return pieces_of_color_and_type(c, KNIGHT);
467 inline Bitboard Position::bishops(Color c) const {
468 return pieces_of_color_and_type(c, BISHOP);
471 inline Bitboard Position::rooks(Color c) const {
472 return pieces_of_color_and_type(c, ROOK);
475 inline Bitboard Position::queens(Color c) const {
476 return pieces_of_color_and_type(c, QUEEN);
479 inline Bitboard Position::kings(Color c) const {
480 return pieces_of_color_and_type(c, KING);
483 inline Bitboard Position::rooks_and_queens(Color c) const {
484 return rooks_and_queens() & pieces_of_color(c);
487 inline Bitboard Position::bishops_and_queens(Color c) const {
488 return bishops_and_queens() & pieces_of_color(c);
491 inline Bitboard Position::sliders_of_color(Color c) const {
492 return sliders() & pieces_of_color(c);
495 inline int Position::piece_count(Color c, PieceType pt) const {
496 return pieceCount[c][pt];
499 inline Square Position::piece_list(Color c, PieceType pt, int index) const {
500 return pieceList[c][pt][index];
503 inline Square Position::ep_square() const {
507 inline Square Position::king_square(Color c) const {
508 return kingSquare[c];
511 inline bool Position::can_castle_kingside(Color side) const {
512 return castleRights & (1+int(side));
515 inline bool Position::can_castle_queenside(Color side) const {
516 return castleRights & (4+4*int(side));
519 inline bool Position::can_castle(Color side) const {
520 return can_castle_kingside(side) || can_castle_queenside(side);
523 inline Square Position::initial_kr_square(Color c) const {
524 return relative_square(c, make_square(initialKRFile, RANK_1));
527 inline Square Position::initial_qr_square(Color c) const {
528 return relative_square(c, make_square(initialQRFile, RANK_1));
531 inline Bitboard Position::pawn_attacks(Color c, Square s) const {
532 return StepAttackBB[piece_of_color_and_type(c, PAWN)][s];
536 inline Bitboard Position::piece_attacks<PAWN>(Square s) const {
537 return StepAttackBB[piece_of_color_and_type(opposite_color(sideToMove), PAWN)][s];
541 inline Bitboard Position::piece_attacks<KNIGHT>(Square s) const {
542 return StepAttackBB[KNIGHT][s];
546 inline Bitboard Position::piece_attacks<BISHOP>(Square s) const {
547 return bishop_attacks_bb(s, occupied_squares());
551 inline Bitboard Position::piece_attacks<ROOK>(Square s) const {
552 return rook_attacks_bb(s, occupied_squares());
556 inline Bitboard Position::piece_attacks<QUEEN>(Square s) const {
557 return piece_attacks<ROOK>(s) | piece_attacks<BISHOP>(s);
561 inline Bitboard Position::piece_attacks<KING>(Square s) const {
562 return StepAttackBB[KING][s];
565 inline Bitboard Position::checkers() const {
569 inline bool Position::is_check() const {
570 return checkersBB != EmptyBoardBB;
573 inline bool Position::pawn_attacks_square(Color c, Square f, Square t) const {
574 return bit_is_set(pawn_attacks(c, f), t);
577 template<PieceType Piece>
578 Bitboard Position::piece_attacks_square(Square f, Square t) const {
579 return bit_is_set(piece_attacks<Piece>(f), t);
582 inline Bitboard Position::attacks_to(Square s, Color c) const {
584 return attacks_to(s) & pieces_of_color(c);
587 inline bool Position::square_is_attacked(Square s, Color c) const {
589 return attacks_to(s, c) != EmptyBoardBB;
592 inline bool Position::pawn_is_passed(Color c, Square s) const {
593 return !(pawns(opposite_color(c)) & passed_pawn_mask(c, s));
596 inline bool Position::pawn_is_isolated(Color c, Square s) const {
597 return !(pawns(c) & neighboring_files_bb(s));
600 inline bool Position::pawn_is_doubled(Color c, Square s) const {
601 return pawns(c) & squares_behind(c, s);
604 inline bool Position::file_is_open(File f) const {
605 return !(pawns() & file_bb(f));
608 inline bool Position::file_is_half_open(Color c, File f) const {
609 return !(pawns(c) & file_bb(f));
612 inline bool Position::square_is_weak(Square s, Color c) const {
613 return !(pawns(c) & outpost_mask(opposite_color(c), s));
616 inline Key Position::get_key() const {
620 inline Key Position::get_pawn_key() const {
624 inline Key Position::get_material_key() const {
628 inline Value Position::mg_pst(Color c, PieceType pt, Square s) const {
629 return MgPieceSquareTable[piece_of_color_and_type(c, pt)][s];
632 inline Value Position::mg_pst_delta(Move m) const {
633 return MgPieceSquareTable[piece_on(move_from(m))][move_to(m)]
634 -MgPieceSquareTable[piece_on(move_from(m))][move_from(m)];
637 inline Value Position::eg_pst(Color c, PieceType pt, Square s) const {
638 return EgPieceSquareTable[piece_of_color_and_type(c, pt)][s];
641 inline Value Position::mg_value() const {
645 inline Value Position::eg_value() const {
649 inline Value Position::non_pawn_material(Color c) const {
650 return npMaterial[c];
653 inline Phase Position::game_phase() const {
655 // The purpose of the Value(325) terms below is to make sure the difference
656 // between MidgameLimit and EndgameLimit is a power of 2, which should make
657 // the division at the end of the function a bit faster.
658 static const Value MidgameLimit = 2 * QueenValueMidgame
659 + 2 * RookValueMidgame
660 + 6 * BishopValueMidgame
663 static const Value EndgameLimit = 4 * RookValueMidgame - Value(325);
665 Value npm = non_pawn_material(WHITE) + non_pawn_material(BLACK);
667 if (npm >= MidgameLimit)
668 return PHASE_MIDGAME;
669 else if(npm <= EndgameLimit)
670 return PHASE_ENDGAME;
672 return Phase(((npm - EndgameLimit) * 128) / (MidgameLimit - EndgameLimit));
675 inline bool Position::move_is_deep_pawn_push(Move m) const {
677 Color c = side_to_move();
678 return piece_on(move_from(m)) == piece_of_color_and_type(c, PAWN)
679 && relative_rank(c, move_to(m)) > RANK_4;
682 inline bool Position::move_is_pawn_push_to_7th(Move m) const {
684 Color c = side_to_move();
685 return piece_on(move_from(m)) == piece_of_color_and_type(c, PAWN)
686 && relative_rank(c, move_to(m)) == RANK_7;
689 inline bool Position::move_is_passed_pawn_push(Move m) const {
691 Color c = side_to_move();
692 return piece_on(move_from(m)) == piece_of_color_and_type(c, PAWN)
693 && pawn_is_passed(c, move_to(m));
696 inline bool Position::move_was_passed_pawn_push(Move m) const {
698 Color c = opposite_color(side_to_move());
699 return piece_on(move_to(m)) == piece_of_color_and_type(c, PAWN)
700 && pawn_is_passed(c, move_to(m));
703 inline int Position::rule_50_counter() const {
708 inline bool Position::opposite_colored_bishops() const {
710 return piece_count(WHITE, BISHOP) == 1
711 && piece_count(BLACK, BISHOP) == 1
712 && square_color(piece_list(WHITE, BISHOP, 0)) != square_color(piece_list(BLACK, BISHOP, 0));
715 inline bool Position::has_pawn_on_7th(Color c) const {
717 return pawns(c) & relative_rank_bb(c, RANK_7);
721 #endif // !defined(POSITION_H_INCLUDED)