2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2009 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 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 /// Castle rights, encoded as bit fields
84 /// The StateInfo struct stores information we need to restore a Position
85 /// object to its previous state when we retract a move. Whenever a move
86 /// is made on the board (by calling Position::do_move), an StateInfo object
87 /// must be passed as a parameter.
90 Key key, pawnKey, materialKey;
91 int castleRights, rule50;
93 Value mgValue, egValue;
102 /// The position data structure. A position consists of the following data:
104 /// * For each piece type, a bitboard representing the squares occupied
105 /// by pieces of that type.
106 /// * For each color, a bitboard representing the squares occupied by
107 /// pieces of that color.
108 /// * A bitboard of all occupied squares.
109 /// * A bitboard of all checking pieces.
110 /// * A 64-entry array of pieces, indexed by the squares of the board.
111 /// * The current side to move.
112 /// * Information about the castling rights for both sides.
113 /// * The initial files of the kings and both pairs of rooks. This is
114 /// used to implement the Chess960 castling rules.
115 /// * The en passant square (which is SQ_NONE if no en passant capture is
117 /// * The squares of the kings for both sides.
118 /// * Hash keys for the position itself, the current pawn structure, and
119 /// the current material situation.
120 /// * Hash keys for all previous positions in the game for detecting
121 /// repetition draws.
122 /// * A counter for detecting 50 move rule draws.
126 friend class MaterialInfo;
127 friend class EndgameFunctions;
132 Position(const Position& pos);
133 Position(const std::string& fen);
136 void from_fen(const std::string& fen);
137 const std::string to_fen() const;
138 void print(Move m = MOVE_NONE) const;
141 void copy(const Position &pos);
142 void flipped_copy(const Position &pos);
144 // The piece on a given square
145 Piece piece_on(Square s) const;
146 PieceType type_of_piece_on(Square s) const;
147 Color color_of_piece_on(Square s) const;
148 bool square_is_empty(Square s) const;
149 bool square_is_occupied(Square s) const;
150 Value midgame_value_of_piece_on(Square s) const;
151 Value endgame_value_of_piece_on(Square s) const;
154 Color side_to_move() const;
156 // Bitboard representation of the position
157 Bitboard empty_squares() const;
158 Bitboard occupied_squares() const;
159 Bitboard pieces_of_color(Color c) const;
160 Bitboard pieces_of_type(PieceType pt) const;
161 Bitboard pieces_of_color_and_type(Color c, PieceType pt) const;
162 Bitboard pawns() const;
163 Bitboard knights() const;
164 Bitboard bishops() const;
165 Bitboard rooks() const;
166 Bitboard queens() const;
167 Bitboard kings() const;
168 Bitboard rooks_and_queens() const;
169 Bitboard bishops_and_queens() const;
170 Bitboard sliders() const;
171 Bitboard pawns(Color c) const;
172 Bitboard knights(Color c) const;
173 Bitboard bishops(Color c) const;
174 Bitboard rooks(Color c) const;
175 Bitboard queens(Color c) const;
176 Bitboard kings(Color c) const;
177 Bitboard rooks_and_queens(Color c) const;
178 Bitboard bishops_and_queens(Color c) const;
179 Bitboard sliders_of_color(Color c) const;
181 // Number of pieces of each color and type
182 int piece_count(Color c, PieceType pt) const;
184 // The en passant square
185 Square ep_square() const;
187 // Current king position for each color
188 Square king_square(Color c) const;
191 bool can_castle_kingside(Color c) const;
192 bool can_castle_queenside(Color c) const;
193 bool can_castle(Color c) const;
194 Square initial_kr_square(Color c) const;
195 Square initial_qr_square(Color c) const;
198 Bitboard sliding_attacks(Square s, Direction d) const;
199 Bitboard ray_attacks(Square s, SignedDirection d) const;
200 Bitboard pawn_attacks(Color c, Square s) const;
203 Bitboard piece_attacks(Square s) const;
205 // Bitboards for pinned pieces and discovered check candidates
206 Bitboard discovered_check_candidates(Color c) const;
207 Bitboard pinned_pieces(Color c, Bitboard& p) const;
208 Bitboard pinned_pieces(Color c) const;
211 Bitboard checkers() const;
214 Square piece_list(Color c, PieceType pt, int index) const;
216 // Attack information for a given square
217 bool square_is_attacked(Square s, Color c) const;
218 Bitboard attacks_to(Square s) const;
219 Bitboard attacks_to(Square s, Color c) const;
220 bool is_check() const;
221 bool pawn_attacks_square(Color c, Square f, Square t) const;
224 Bitboard piece_attacks_square(Square f, Square t) const; // Dispatch at compile-time
226 bool piece_attacks_square(Piece p, Square f, Square t) const; // Dispatch at run-time
228 // Properties of moves
229 bool pl_move_is_legal(Move m) const;
230 bool pl_move_is_legal(Move m, Bitboard pinned) const;
231 bool move_is_check(Move m) const;
232 bool move_is_check(Move m, Bitboard dcCandidates) const;
233 bool move_is_capture(Move m) const;
234 bool move_is_deep_pawn_push(Move m) const;
235 bool move_is_pawn_push_to_7th(Move m) const;
236 bool move_is_passed_pawn_push(Move m) const;
237 bool move_was_passed_pawn_push(Move m) const;
238 bool move_attacks_square(Move m, Square s) const;
240 // Information about pawns
241 bool pawn_is_passed(Color c, Square s) const;
242 bool pawn_is_isolated(Color c, Square s) const;
243 bool pawn_is_doubled(Color c, Square s) const;
245 // Open and half-open files
246 bool file_is_open(File f) const;
247 bool file_is_half_open(Color c, File f) const;
250 bool square_is_weak(Square s, Color c) const;
252 // Doing and undoing moves
253 void setStartState(const StateInfo& st);
254 void do_move(Move m, StateInfo& st);
255 void do_move(Move m, StateInfo& st, Bitboard dcCandidates);
256 void undo_move(Move m);
257 void do_null_move(StateInfo& st);
258 void undo_null_move();
260 // Static exchange evaluation
261 int see(Square from, Square to) const;
262 int see(Move m) const;
263 int see(Square to) const;
265 // Accessing hash keys
267 Key get_pawn_key() const;
268 Key get_material_key() const;
270 // Incremental evaluation
271 Value mg_value() const;
272 Value eg_value() const;
273 Value non_pawn_material(Color c) const;
274 Phase game_phase() const;
275 Value mg_pst_delta(Move m) const;
277 // Game termination checks
278 bool is_mate() const;
279 bool is_draw() const;
281 // Check if one side threatens a mate in one
282 bool has_mate_threat(Color c);
284 // Number of plies since the last non-reversible move
285 int rule_50_counter() const;
287 // Other properties of the position
288 bool opposite_colored_bishops() const;
289 bool has_pawn_on_7th(Color c) const;
291 // Reset the gamePly variable to 0
292 void reset_game_ply();
294 // Position consistency check, for debugging
295 bool is_ok(int* failedStep = NULL) const;
297 // Static member functions:
298 static void init_zobrist();
299 static void init_piece_square_tables();
303 // Initialization helper functions (used while setting up a position)
305 void put_piece(Piece p, Square s);
306 void allow_oo(Color c);
307 void allow_ooo(Color c);
309 // Helper functions for doing and undoing moves
310 void do_capture_move(PieceType capture, Color them, Square to);
311 void do_castle_move(Move m);
312 void do_promotion_move(Move m);
313 void do_ep_move(Move m);
314 void undo_castle_move(Move m);
315 void undo_promotion_move(Move m);
316 void undo_ep_move(Move m);
317 void find_checkers();
319 template<PieceType Piece>
320 void update_checkers(Bitboard* pCheckersBB, Square ksq, Square from, Square to, Bitboard dcCandidates);
322 template<bool FindPinned>
323 Bitboard hidden_checkers(Color c) const;
325 // Computing hash keys from scratch (for initialization and debugging)
326 Key compute_key() const;
327 Key compute_pawn_key() const;
328 Key compute_material_key() const;
330 // Computing incremental evaluation scores and material counts
335 template<GamePhase> Value pst(Color c, PieceType pt, Square s) const;
336 template<GamePhase> Value compute_value() const;
337 Value compute_non_pawn_material(Color c) const;
340 Bitboard byColorBB[2], byTypeBB[8];
346 int pieceCount[2][8]; // [color][pieceType]
349 Square pieceList[2][8][16]; // [color][pieceType][index]
353 Square kingSquare[2];
356 Key history[MaxGameLength];
357 File initialKFile, initialKRFile, initialQRFile;
358 StateInfo startState;
362 static int castleRightsMask[64];
363 static Key zobrist[2][8][64];
364 static Key zobEp[64];
365 static Key zobCastle[16];
366 static Key zobMaterial[2][8][16];
367 static Key zobSideToMove;
368 static Value MgPieceSquareTable[16][64];
369 static Value EgPieceSquareTable[16][64];
374 //// Inline functions
377 inline Piece Position::piece_on(Square s) const {
381 inline Color Position::color_of_piece_on(Square s) const {
382 return color_of_piece(piece_on(s));
385 inline PieceType Position::type_of_piece_on(Square s) const {
386 return type_of_piece(piece_on(s));
389 inline bool Position::square_is_empty(Square s) const {
390 return piece_on(s) == EMPTY;
393 inline bool Position::square_is_occupied(Square s) const {
394 return !square_is_empty(s);
397 inline Value Position::midgame_value_of_piece_on(Square s) const {
398 return piece_value_midgame(piece_on(s));
401 inline Value Position::endgame_value_of_piece_on(Square s) const {
402 return piece_value_endgame(piece_on(s));
405 inline Color Position::side_to_move() const {
409 inline Bitboard Position::occupied_squares() const {
413 inline Bitboard Position::empty_squares() const {
414 return ~(occupied_squares());
417 inline Bitboard Position::pieces_of_color(Color c) const {
421 inline Bitboard Position::pieces_of_type(PieceType pt) const {
425 inline Bitboard Position::pieces_of_color_and_type(Color c, PieceType pt) const {
426 return pieces_of_color(c) & pieces_of_type(pt);
429 inline Bitboard Position::pawns() const {
430 return pieces_of_type(PAWN);
433 inline Bitboard Position::knights() const {
434 return pieces_of_type(KNIGHT);
437 inline Bitboard Position::bishops() const {
438 return pieces_of_type(BISHOP);
441 inline Bitboard Position::rooks() const {
442 return pieces_of_type(ROOK);
445 inline Bitboard Position::queens() const {
446 return pieces_of_type(QUEEN);
449 inline Bitboard Position::kings() const {
450 return pieces_of_type(KING);
453 inline Bitboard Position::rooks_and_queens() const {
454 return rooks() | queens();
457 inline Bitboard Position::bishops_and_queens() const {
458 return bishops() | queens();
461 inline Bitboard Position::sliders() const {
462 return bishops() | queens() | rooks();
465 inline Bitboard Position::pawns(Color c) const {
466 return pieces_of_color_and_type(c, PAWN);
469 inline Bitboard Position::knights(Color c) const {
470 return pieces_of_color_and_type(c, KNIGHT);
473 inline Bitboard Position::bishops(Color c) const {
474 return pieces_of_color_and_type(c, BISHOP);
477 inline Bitboard Position::rooks(Color c) const {
478 return pieces_of_color_and_type(c, ROOK);
481 inline Bitboard Position::queens(Color c) const {
482 return pieces_of_color_and_type(c, QUEEN);
485 inline Bitboard Position::kings(Color c) const {
486 return pieces_of_color_and_type(c, KING);
489 inline Bitboard Position::rooks_and_queens(Color c) const {
490 return rooks_and_queens() & pieces_of_color(c);
493 inline Bitboard Position::bishops_and_queens(Color c) const {
494 return bishops_and_queens() & pieces_of_color(c);
497 inline int Position::piece_count(Color c, PieceType pt) const {
498 return pieceCount[c][pt];
501 inline Square Position::piece_list(Color c, PieceType pt, int index) const {
502 return pieceList[c][pt][index];
505 inline Square Position::ep_square() const {
509 inline Square Position::king_square(Color c) const {
510 return kingSquare[c];
513 inline bool Position::can_castle_kingside(Color side) const {
514 return st->castleRights & (1+int(side));
517 inline bool Position::can_castle_queenside(Color side) const {
518 return st->castleRights & (4+4*int(side));
521 inline bool Position::can_castle(Color side) const {
522 return can_castle_kingside(side) || can_castle_queenside(side);
525 inline Square Position::initial_kr_square(Color c) const {
526 return relative_square(c, make_square(initialKRFile, RANK_1));
529 inline Square Position::initial_qr_square(Color c) const {
530 return relative_square(c, make_square(initialQRFile, RANK_1));
533 inline Bitboard Position::pawn_attacks(Color c, Square s) const {
534 return StepAttackBB[piece_of_color_and_type(c, PAWN)][s];
537 template<PieceType Piece> // Knight and King
538 inline Bitboard Position::piece_attacks(Square s) const {
539 return StepAttackBB[Piece][s];
543 inline Bitboard Position::piece_attacks<PAWN>(Square s) const {
544 return StepAttackBB[piece_of_color_and_type(opposite_color(sideToMove), PAWN)][s];
548 inline Bitboard Position::piece_attacks<BISHOP>(Square s) const {
549 return bishop_attacks_bb(s, occupied_squares());
553 inline Bitboard Position::piece_attacks<ROOK>(Square s) const {
554 return rook_attacks_bb(s, occupied_squares());
558 inline Bitboard Position::piece_attacks<QUEEN>(Square s) const {
559 return piece_attacks<ROOK>(s) | piece_attacks<BISHOP>(s);
562 inline Bitboard Position::checkers() const {
563 return st->checkersBB;
566 inline bool Position::is_check() const {
567 return st->checkersBB != EmptyBoardBB;
570 inline bool Position::pawn_attacks_square(Color c, Square f, Square t) const {
571 return bit_is_set(pawn_attacks(c, f), t);
574 template<PieceType Piece>
575 Bitboard Position::piece_attacks_square(Square f, Square t) const {
576 return bit_is_set(piece_attacks<Piece>(f), t);
579 inline Bitboard Position::attacks_to(Square s, Color c) const {
581 return attacks_to(s) & pieces_of_color(c);
584 inline bool Position::square_is_attacked(Square s, Color c) const {
586 return attacks_to(s, c) != EmptyBoardBB;
589 inline bool Position::pawn_is_passed(Color c, Square s) const {
590 return !(pawns(opposite_color(c)) & passed_pawn_mask(c, s));
593 inline bool Position::pawn_is_isolated(Color c, Square s) const {
594 return !(pawns(c) & neighboring_files_bb(s));
597 inline bool Position::pawn_is_doubled(Color c, Square s) const {
598 return pawns(c) & squares_behind(c, s);
601 inline bool Position::file_is_open(File f) const {
602 return !(pawns() & file_bb(f));
605 inline bool Position::file_is_half_open(Color c, File f) const {
606 return !(pawns(c) & file_bb(f));
609 inline bool Position::square_is_weak(Square s, Color c) const {
610 return !(pawns(c) & outpost_mask(opposite_color(c), s));
613 inline Key Position::get_key() const {
617 inline Key Position::get_pawn_key() const {
621 inline Key Position::get_material_key() const {
622 return st->materialKey;
625 template<Position::GamePhase Phase>
626 inline Value Position::pst(Color c, PieceType pt, Square s) const {
627 return (Phase == MidGame ? MgPieceSquareTable[piece_of_color_and_type(c, pt)][s]
628 : EgPieceSquareTable[piece_of_color_and_type(c, pt)][s]);
631 inline Value Position::mg_pst_delta(Move m) const {
632 return MgPieceSquareTable[piece_on(move_from(m))][move_to(m)]
633 -MgPieceSquareTable[piece_on(move_from(m))][move_from(m)];
636 inline Value Position::mg_value() const {
640 inline Value Position::eg_value() const {
644 inline Value Position::non_pawn_material(Color c) const {
645 return st->npMaterial[c];
648 inline Phase Position::game_phase() const {
650 // Values modified by Joona Kiiski
651 static const Value MidgameLimit = Value(15713);
652 static const Value EndgameLimit = Value(4428);
654 Value npm = non_pawn_material(WHITE) + non_pawn_material(BLACK);
656 if (npm >= MidgameLimit)
657 return PHASE_MIDGAME;
658 else if(npm <= EndgameLimit)
659 return PHASE_ENDGAME;
661 return Phase(((npm - EndgameLimit) * 128) / (MidgameLimit - EndgameLimit));
664 inline bool Position::move_is_deep_pawn_push(Move m) const {
666 Color c = side_to_move();
667 return piece_on(move_from(m)) == piece_of_color_and_type(c, PAWN)
668 && relative_rank(c, move_to(m)) > RANK_4;
671 inline bool Position::move_is_pawn_push_to_7th(Move m) const {
673 Color c = side_to_move();
674 return piece_on(move_from(m)) == piece_of_color_and_type(c, PAWN)
675 && relative_rank(c, move_to(m)) == RANK_7;
678 inline bool Position::move_is_passed_pawn_push(Move m) const {
680 Color c = side_to_move();
681 return piece_on(move_from(m)) == piece_of_color_and_type(c, PAWN)
682 && pawn_is_passed(c, move_to(m));
685 inline bool Position::move_was_passed_pawn_push(Move m) const {
687 Color c = opposite_color(side_to_move());
688 return piece_on(move_to(m)) == piece_of_color_and_type(c, PAWN)
689 && pawn_is_passed(c, move_to(m));
692 inline int Position::rule_50_counter() const {
697 inline bool Position::opposite_colored_bishops() const {
699 return piece_count(WHITE, BISHOP) == 1
700 && piece_count(BLACK, BISHOP) == 1
701 && square_color(piece_list(WHITE, BISHOP, 0)) != square_color(piece_list(BLACK, BISHOP, 0));
704 inline bool Position::has_pawn_on_7th(Color c) const {
706 return pawns(c) & relative_rank_bb(c, RANK_7);
709 inline bool Position::move_is_capture(Move m) const {
711 // Move must not be MOVE_NONE !
713 return (!square_is_empty(move_to(m)) && !move_is_castle(m)) || move_is_ep(m);
716 #endif // !defined(POSITION_H_INCLUDED)