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;
137 Position(const Position& pos);
138 Position(const std::string& fen);
141 void from_fen(const std::string& fen);
142 const std::string to_fen() const;
143 void print(Move m = MOVE_NONE) const;
146 void copy(const Position& pos);
147 void flipped_copy(const Position& pos);
149 // The piece on a given square
150 Piece piece_on(Square s) const;
151 PieceType type_of_piece_on(Square s) const;
152 Color color_of_piece_on(Square s) const;
153 bool square_is_empty(Square s) const;
154 bool square_is_occupied(Square s) const;
155 Value midgame_value_of_piece_on(Square s) const;
156 Value endgame_value_of_piece_on(Square s) const;
159 Color side_to_move() const;
161 // Bitboard representation of the position
162 Bitboard empty_squares() const;
163 Bitboard occupied_squares() const;
164 Bitboard pieces_of_color(Color c) const;
165 Bitboard pieces_of_type(PieceType pt) const;
166 Bitboard pawns() const;
167 Bitboard knights() const;
168 Bitboard bishops() const;
169 Bitboard rooks() const;
170 Bitboard queens() const;
171 Bitboard kings() const;
172 Bitboard rooks_and_queens() const;
173 Bitboard bishops_and_queens() const;
174 Bitboard sliders() const;
175 Bitboard pawns(Color c) const;
176 Bitboard knights(Color c) const;
177 Bitboard bishops(Color c) const;
178 Bitboard rooks(Color c) const;
179 Bitboard queens(Color c) const;
180 Bitboard kings(Color c) const;
181 Bitboard rooks_and_queens(Color c) const;
182 Bitboard bishops_and_queens(Color c) const;
183 Bitboard sliders_of_color(Color c) const;
185 // Number of pieces of each color and type
186 int piece_count(Color c, PieceType pt) const;
188 // The en passant square
189 Square ep_square() const;
191 // Current king position for each color
192 Square king_square(Color c) const;
195 bool can_castle_kingside(Color c) const;
196 bool can_castle_queenside(Color c) const;
197 bool can_castle(Color c) const;
198 Square initial_kr_square(Color c) const;
199 Square initial_qr_square(Color c) const;
202 Bitboard sliding_attacks(Square s, Direction d) const;
203 Bitboard ray_attacks(Square s, SignedDirection d) const;
204 Bitboard pawn_attacks(Color c, Square s) const;
207 Bitboard piece_attacks(Square s) const;
209 // Bitboards for pinned pieces and discovered check candidates
210 Bitboard discovered_check_candidates(Color c) const;
211 Bitboard pinned_pieces(Color c, Bitboard& p) const;
212 Bitboard pinned_pieces(Color c) const;
215 Bitboard checkers() const;
218 Square piece_list(Color c, PieceType pt, int index) const;
220 // Attack information for a given square
221 bool square_is_attacked(Square s, Color c) const;
222 Bitboard attacks_to(Square s) const;
223 Bitboard attacks_to(Square s, Color c) const;
224 bool is_check() const;
225 bool pawn_attacks_square(Color c, Square f, Square t) const;
228 Bitboard piece_attacks_square(Square f, Square t) const; // Dispatch at compile-time
230 bool piece_attacks_square(Piece p, Square f, Square t) const; // Dispatch at run-time
232 // Properties of moves
233 bool pl_move_is_legal(Move m) const;
234 bool pl_move_is_legal(Move m, Bitboard pinned) const;
235 bool move_is_check(Move m) const;
236 bool move_is_check(Move m, Bitboard dcCandidates) const;
237 bool move_is_capture(Move m) const;
238 bool move_is_passed_pawn_push(Move m) const;
239 bool move_attacks_square(Move m, Square s) const;
241 // Information about pawns
242 bool pawn_is_passed(Color c, Square s) const;
243 static bool pawn_is_passed(Bitboard theirPawns, Color c, Square s);
244 static bool pawn_is_isolated(Bitboard ourPawns, Square s);
245 static bool pawn_is_doubled(Bitboard ourPawns, Color c, Square s);
248 bool square_is_weak(Square s, Color c) const;
250 // Doing and undoing moves
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;
262 int see_sign(Move m) const;
264 // Accessing hash keys
266 Key get_pawn_key() const;
267 Key get_material_key() const;
269 // Incremental evaluation
270 Value mg_value() const;
271 Value eg_value() const;
272 Value non_pawn_material(Color c) const;
273 Phase game_phase() const;
274 template<GamePhase> Value pst_delta(Piece piece, Square from, Square to) const;
276 // Game termination checks
277 bool is_mate() const;
278 bool is_draw() const;
280 // Check if one side threatens a mate in one
281 bool has_mate_threat(Color c);
283 // Number of plies since the last non-reversible move
284 int rule_50_counter() const;
286 // Other properties of the position
287 bool opposite_colored_bishops() const;
288 bool has_pawn_on_7th(Color c) const;
290 // Reset the gamePly variable to 0
291 void reset_game_ply();
293 // Position consistency check, for debugging
294 bool is_ok(int* failedStep = NULL) const;
296 // Static member functions:
297 static void init_zobrist();
298 static void init_piece_square_tables();
302 // Initialization helper functions (used while setting up a position)
304 void put_piece(Piece p, Square s);
305 void allow_oo(Color c);
306 void allow_ooo(Color c);
308 // Helper functions for doing and undoing moves
309 void do_capture_move(Bitboard& key, PieceType capture, Color them, Square to, bool ep);
310 void do_castle_move(Move m);
311 void undo_castle_move(Move m);
312 void find_checkers();
314 template<PieceType Piece>
315 void update_checkers(Bitboard* pCheckersBB, Square ksq, Square from, Square to, Bitboard dcCandidates);
317 template<bool FindPinned>
318 Bitboard hidden_checkers(Color c) const;
320 // Computing hash keys from scratch (for initialization and debugging)
321 Key compute_key() const;
322 Key compute_pawn_key() const;
323 Key compute_material_key() const;
325 // Computing incremental evaluation scores and material counts
326 template<GamePhase> Value pst(Color c, PieceType pt, Square s) const;
327 template<GamePhase> Value compute_value() const;
328 Value compute_non_pawn_material(Color c) const;
331 Bitboard byColorBB[2], byTypeBB[8];
337 int pieceCount[2][8]; // [color][pieceType]
340 Square pieceList[2][8][16]; // [color][pieceType][index]
341 int index[64]; // [square]
344 Square kingSquare[2];
347 Key history[MaxGameLength];
348 File initialKFile, initialKRFile, initialQRFile;
349 StateInfo startState;
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::pawns() const {
417 return pieces_of_type(PAWN);
420 inline Bitboard Position::knights() const {
421 return pieces_of_type(KNIGHT);
424 inline Bitboard Position::bishops() const {
425 return pieces_of_type(BISHOP);
428 inline Bitboard Position::rooks() const {
429 return pieces_of_type(ROOK);
432 inline Bitboard Position::queens() const {
433 return pieces_of_type(QUEEN);
436 inline Bitboard Position::kings() const {
437 return pieces_of_type(KING);
440 inline Bitboard Position::rooks_and_queens() const {
441 return rooks() | queens();
444 inline Bitboard Position::bishops_and_queens() const {
445 return bishops() | queens();
448 inline Bitboard Position::sliders() const {
449 return bishops() | queens() | rooks();
452 inline Bitboard Position::pawns(Color c) const {
453 return pieces_of_color(c) & pieces_of_type(PAWN);
456 inline Bitboard Position::knights(Color c) const {
457 return pieces_of_color(c) & pieces_of_type(KNIGHT);
460 inline Bitboard Position::bishops(Color c) const {
461 return pieces_of_color(c) & pieces_of_type(BISHOP);
464 inline Bitboard Position::rooks(Color c) const {
465 return pieces_of_color(c) & pieces_of_type(ROOK);
468 inline Bitboard Position::queens(Color c) const {
469 return pieces_of_color(c) & pieces_of_type(QUEEN);
472 inline Bitboard Position::kings(Color c) const {
473 return pieces_of_color(c) & pieces_of_type(KING);
476 inline Bitboard Position::rooks_and_queens(Color c) const {
477 return pieces_of_color(c) & rooks_and_queens();
480 inline Bitboard Position::bishops_and_queens(Color c) const {
481 return pieces_of_color(c) & bishops_and_queens();
484 inline int Position::piece_count(Color c, PieceType pt) const {
485 return pieceCount[c][pt];
488 inline Square Position::piece_list(Color c, PieceType pt, int index) const {
489 return pieceList[c][pt][index];
492 inline Square Position::ep_square() const {
496 inline Square Position::king_square(Color c) const {
497 return kingSquare[c];
500 inline bool Position::can_castle_kingside(Color side) const {
501 return st->castleRights & (1+int(side));
504 inline bool Position::can_castle_queenside(Color side) const {
505 return st->castleRights & (4+4*int(side));
508 inline bool Position::can_castle(Color side) const {
509 return can_castle_kingside(side) || can_castle_queenside(side);
512 inline Square Position::initial_kr_square(Color c) const {
513 return relative_square(c, make_square(initialKRFile, RANK_1));
516 inline Square Position::initial_qr_square(Color c) const {
517 return relative_square(c, make_square(initialQRFile, RANK_1));
520 inline Bitboard Position::pawn_attacks(Color c, Square s) const {
521 return StepAttackBB[piece_of_color_and_type(c, PAWN)][s];
524 template<PieceType Piece> // Knight and King
525 inline Bitboard Position::piece_attacks(Square s) const {
526 return StepAttackBB[Piece][s];
530 inline Bitboard Position::piece_attacks<PAWN>(Square s) const {
531 return StepAttackBB[piece_of_color_and_type(opposite_color(sideToMove), PAWN)][s];
535 inline Bitboard Position::piece_attacks<BISHOP>(Square s) const {
536 return bishop_attacks_bb(s, occupied_squares());
540 inline Bitboard Position::piece_attacks<ROOK>(Square s) const {
541 return rook_attacks_bb(s, occupied_squares());
545 inline Bitboard Position::piece_attacks<QUEEN>(Square s) const {
546 return piece_attacks<ROOK>(s) | piece_attacks<BISHOP>(s);
549 inline Bitboard Position::checkers() const {
550 return st->checkersBB;
553 inline bool Position::is_check() const {
554 return st->checkersBB != EmptyBoardBB;
557 inline bool Position::pawn_attacks_square(Color c, Square f, Square t) const {
558 return bit_is_set(pawn_attacks(c, f), t);
561 template<PieceType Piece>
562 Bitboard Position::piece_attacks_square(Square f, Square t) const {
563 return bit_is_set(piece_attacks<Piece>(f), t);
566 inline Bitboard Position::attacks_to(Square s, Color c) const {
568 return attacks_to(s) & pieces_of_color(c);
571 inline bool Position::square_is_attacked(Square s, Color c) const {
573 return attacks_to(s, c) != EmptyBoardBB;
576 inline bool Position::pawn_is_passed(Color c, Square s) const {
577 return !(pawns(opposite_color(c)) & passed_pawn_mask(c, s));
580 inline bool Position::pawn_is_passed(Bitboard theirPawns, Color c, Square s) {
581 return !(theirPawns & passed_pawn_mask(c, s));
584 inline bool Position::pawn_is_isolated(Bitboard ourPawns, Square s) {
585 return !(ourPawns & neighboring_files_bb(s));
588 inline bool Position::pawn_is_doubled(Bitboard ourPawns, Color c, Square s) {
589 return ourPawns & squares_behind(c, s);
592 inline bool Position::square_is_weak(Square s, Color c) const {
593 return !(pawns(c) & outpost_mask(opposite_color(c), s));
596 inline Key Position::get_key() const {
600 inline Key Position::get_pawn_key() const {
604 inline Key Position::get_material_key() const {
605 return st->materialKey;
608 template<Position::GamePhase Ph>
609 inline Value Position::pst(Color c, PieceType pt, Square s) const {
610 return (Ph == MidGame ? MgPieceSquareTable[piece_of_color_and_type(c, pt)][s]
611 : EgPieceSquareTable[piece_of_color_and_type(c, pt)][s]);
614 template<Position::GamePhase Ph>
615 inline Value Position::pst_delta(Piece piece, Square from, Square to) const {
616 return (Ph == MidGame ? MgPieceSquareTable[piece][to] - MgPieceSquareTable[piece][from]
617 : EgPieceSquareTable[piece][to] - EgPieceSquareTable[piece][from]);
620 inline Value Position::mg_value() const {
624 inline Value Position::eg_value() const {
628 inline Value Position::non_pawn_material(Color c) const {
629 return st->npMaterial[c];
632 inline Phase Position::game_phase() const {
634 // Values modified by Joona Kiiski
635 static const Value MidgameLimit = Value(15581);
636 static const Value EndgameLimit = Value(3998);
638 Value npm = non_pawn_material(WHITE) + non_pawn_material(BLACK);
640 if (npm >= MidgameLimit)
641 return PHASE_MIDGAME;
642 else if(npm <= EndgameLimit)
643 return PHASE_ENDGAME;
645 return Phase(((npm - EndgameLimit) * 128) / (MidgameLimit - EndgameLimit));
648 inline bool Position::move_is_passed_pawn_push(Move m) const {
650 Color c = side_to_move();
651 return piece_on(move_from(m)) == piece_of_color_and_type(c, PAWN)
652 && pawn_is_passed(c, move_to(m));
655 inline int Position::rule_50_counter() const {
660 inline bool Position::opposite_colored_bishops() const {
662 return piece_count(WHITE, BISHOP) == 1
663 && piece_count(BLACK, BISHOP) == 1
664 && square_color(piece_list(WHITE, BISHOP, 0)) != square_color(piece_list(BLACK, BISHOP, 0));
667 inline bool Position::has_pawn_on_7th(Color c) const {
669 return pawns(c) & relative_rank_bb(c, RANK_7);
672 inline bool Position::move_is_capture(Move m) const {
674 // Move must not be MOVE_NONE !
676 return (!square_is_empty(move_to(m)) && !move_is_castle(m)) || move_is_ep(m);
679 #endif // !defined(POSITION_H_INCLUDED)