2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2010 Marco Costalba, Joona Kiiski, Tord Romstad
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 StartPositionFEN = "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 /// struct checkInfo is initialized at c'tor time and keeps
67 /// info used to detect if a move gives check.
71 explicit CheckInfo(const Position&);
73 Bitboard dcCandidates;
78 /// Castle rights, encoded as bit fields
96 /// The StateInfo struct stores information we need to restore a Position
97 /// object to its previous state when we retract a move. Whenever a move
98 /// is made on the board (by calling Position::do_move), an StateInfo object
99 /// must be passed as a parameter.
102 Key pawnKey, materialKey;
103 int castleRights, rule50, gamePly, pliesFromNull;
115 /// The position data structure. A position consists of the following data:
117 /// * For each piece type, a bitboard representing the squares occupied
118 /// by pieces of that type.
119 /// * For each color, a bitboard representing the squares occupied by
120 /// pieces of that color.
121 /// * A bitboard of all occupied squares.
122 /// * A bitboard of all checking pieces.
123 /// * A 64-entry array of pieces, indexed by the squares of the board.
124 /// * The current side to move.
125 /// * Information about the castling rights for both sides.
126 /// * The initial files of the kings and both pairs of rooks. This is
127 /// used to implement the Chess960 castling rules.
128 /// * The en passant square (which is SQ_NONE if no en passant capture is
130 /// * The squares of the kings for both sides.
131 /// * Hash keys for the position itself, the current pawn structure, and
132 /// the current material situation.
133 /// * Hash keys for all previous positions in the game for detecting
134 /// repetition draws.
135 /// * A counter for detecting 50 move rule draws.
139 friend class MaterialInfo;
140 friend class EndgameFunctions;
142 Position(); // No default or copy c'tor allowed
143 Position(const Position& pos);
152 explicit Position(int threadID);
153 Position(const Position& pos, int threadID);
154 Position(const std::string& fen, int threadID);
157 void from_fen(const std::string& fen);
158 const std::string to_fen() const;
159 void print(Move m = MOVE_NONE) const;
162 void flipped_copy(const Position& pos);
164 // The piece on a given square
165 Piece piece_on(Square s) const;
166 PieceType type_of_piece_on(Square s) const;
167 Color color_of_piece_on(Square s) const;
168 bool square_is_empty(Square s) const;
169 bool square_is_occupied(Square s) const;
170 Value midgame_value_of_piece_on(Square s) const;
171 Value endgame_value_of_piece_on(Square s) const;
174 Color side_to_move() const;
176 // Bitboard representation of the position
177 Bitboard empty_squares() const;
178 Bitboard occupied_squares() const;
179 Bitboard pieces_of_color(Color c) const;
180 Bitboard pieces(PieceType pt) const;
181 Bitboard pieces(PieceType pt, Color c) const;
182 Bitboard pieces(PieceType pt1, PieceType pt2) const;
183 Bitboard pieces(PieceType pt1, PieceType pt2, 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;
201 // Bitboards for pinned pieces and discovered check candidates
202 Bitboard discovered_check_candidates(Color c) const;
203 Bitboard pinned_pieces(Color c) const;
205 // Checking pieces and under check information
206 Bitboard checkers() const;
207 bool is_check() const;
210 Square piece_list(Color c, PieceType pt, int index) const;
211 const Square* piece_list_begin(Color c, PieceType pt) const;
213 // Information about attacks to or from a given square
214 Bitboard attackers_to(Square s) const;
215 Bitboard attacks_from(Piece p, Square s) const;
216 template<PieceType> Bitboard attacks_from(Square s) const;
217 template<PieceType> Bitboard attacks_from(Square s, Color c) const;
219 // Properties of moves
220 bool pl_move_is_legal(Move m, Bitboard pinned) const;
221 bool pl_move_is_evasion(Move m, Bitboard pinned) const;
222 bool move_is_check(Move m) const;
223 bool move_is_check(Move m, const CheckInfo& ci) const;
224 bool move_is_capture(Move m) const;
225 bool move_is_capture_or_promotion(Move m) const;
226 bool move_is_passed_pawn_push(Move m) const;
227 bool move_attacks_square(Move m, Square s) const;
229 // Piece captured with previous moves
230 PieceType captured_piece() const;
232 // Information about pawns
233 bool pawn_is_passed(Color c, Square s) const;
236 bool square_is_weak(Square s, Color c) const;
238 // Doing and undoing moves
240 void do_move(Move m, StateInfo& st);
241 void do_move(Move m, StateInfo& st, const CheckInfo& ci, bool moveIsCheck);
242 void undo_move(Move m);
243 void do_null_move(StateInfo& st);
244 void undo_null_move();
246 // Static exchange evaluation
247 int see(Square from, Square to) const;
248 int see(Move m) const;
249 int see(Square to) const;
250 int see_sign(Move m) const;
252 // Accessing hash keys
254 Key get_exclusion_key() const;
255 Key get_pawn_key() const;
256 Key get_material_key() const;
258 // Incremental evaluation
260 Value non_pawn_material(Color c) const;
261 static Score pst_delta(Piece piece, Square from, Square to);
263 // Game termination checks
264 bool is_mate() const;
265 bool is_draw() const;
267 // Check if one side threatens a mate in one
268 bool has_mate_threat(Color c);
270 // Number of plies since the last non-reversible move
271 int rule_50_counter() const;
273 // Other properties of the position
274 bool opposite_colored_bishops() const;
275 bool has_pawn_on_7th(Color c) const;
277 // Current thread ID searching on the position
280 // Reset the gamePly variable to 0
281 void reset_game_ply();
283 // Position consistency check, for debugging
284 bool is_ok(int* failedStep = NULL) const;
286 // Static member functions
287 static void init_zobrist();
288 static void init_piece_square_tables();
292 // Initialization helper functions (used while setting up a position)
294 void put_piece(Piece p, Square s);
295 void allow_oo(Color c);
296 void allow_ooo(Color c);
298 // Helper functions for doing and undoing moves
299 void do_capture_move(Key& key, PieceType capture, Color them, Square to, bool ep);
300 void do_castle_move(Move m);
301 void undo_castle_move(Move m);
302 void find_checkers();
304 template<bool FindPinned>
305 Bitboard hidden_checkers(Color c) const;
307 // Computing hash keys from scratch (for initialization and debugging)
308 Key compute_key() const;
309 Key compute_pawn_key() const;
310 Key compute_material_key() const;
312 // Computing incremental evaluation scores and material counts
313 static Score pst(Color c, PieceType pt, Square s);
314 Score compute_value() const;
315 Value compute_non_pawn_material(Color c) const;
321 Bitboard byTypeBB[8], byColorBB[2];
324 int pieceCount[2][8]; // [color][pieceType]
327 Square pieceList[2][8][16]; // [color][pieceType][index]
328 int index[64]; // [square]
332 Key history[MaxGameLength];
333 int castleRightsMask[64];
334 StateInfo startState;
335 File initialKFile, initialKRFile, initialQRFile;
340 static Key zobrist[2][8][64];
341 static Key zobEp[64];
342 static Key zobCastle[16];
343 static Key zobSideToMove;
344 static Score PieceSquareTable[16][64];
345 static Key zobExclusion;
350 //// Inline functions
353 inline Piece Position::piece_on(Square s) const {
357 inline Color Position::color_of_piece_on(Square s) const {
358 return color_of_piece(piece_on(s));
361 inline PieceType Position::type_of_piece_on(Square s) const {
362 return type_of_piece(piece_on(s));
365 inline bool Position::square_is_empty(Square s) const {
366 return piece_on(s) == EMPTY;
369 inline bool Position::square_is_occupied(Square s) const {
370 return !square_is_empty(s);
373 inline Value Position::midgame_value_of_piece_on(Square s) const {
374 return piece_value_midgame(piece_on(s));
377 inline Value Position::endgame_value_of_piece_on(Square s) const {
378 return piece_value_endgame(piece_on(s));
381 inline Color Position::side_to_move() const {
385 inline Bitboard Position::occupied_squares() const {
389 inline Bitboard Position::empty_squares() const {
390 return ~(occupied_squares());
393 inline Bitboard Position::pieces_of_color(Color c) const {
397 inline Bitboard Position::pieces(PieceType pt) const {
401 inline Bitboard Position::pieces(PieceType pt, Color c) const {
402 return byTypeBB[pt] & byColorBB[c];
405 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2) const {
406 return byTypeBB[pt1] | byTypeBB[pt2];
409 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2, Color c) const {
410 return (byTypeBB[pt1] | byTypeBB[pt2]) & byColorBB[c];
413 inline int Position::piece_count(Color c, PieceType pt) const {
414 return pieceCount[c][pt];
417 inline Square Position::piece_list(Color c, PieceType pt, int idx) const {
418 return pieceList[c][pt][idx];
421 inline const Square* Position::piece_list_begin(Color c, PieceType pt) const {
422 return pieceList[c][pt];
425 inline Square Position::ep_square() const {
429 inline Square Position::king_square(Color c) const {
430 return pieceList[c][KING][0];
433 inline bool Position::can_castle_kingside(Color side) const {
434 return st->castleRights & (1+int(side));
437 inline bool Position::can_castle_queenside(Color side) const {
438 return st->castleRights & (4+4*int(side));
441 inline bool Position::can_castle(Color side) const {
442 return can_castle_kingside(side) || can_castle_queenside(side);
445 inline Square Position::initial_kr_square(Color c) const {
446 return relative_square(c, make_square(initialKRFile, RANK_1));
449 inline Square Position::initial_qr_square(Color c) const {
450 return relative_square(c, make_square(initialQRFile, RANK_1));
454 inline Bitboard Position::attacks_from<PAWN>(Square s, Color c) const {
455 return StepAttackBB[piece_of_color_and_type(c, PAWN)][s];
458 template<PieceType Piece> // Knight and King and white pawns
459 inline Bitboard Position::attacks_from(Square s) const {
460 return StepAttackBB[Piece][s];
464 inline Bitboard Position::attacks_from<BISHOP>(Square s) const {
465 return bishop_attacks_bb(s, occupied_squares());
469 inline Bitboard Position::attacks_from<ROOK>(Square s) const {
470 return rook_attacks_bb(s, occupied_squares());
474 inline Bitboard Position::attacks_from<QUEEN>(Square s) const {
475 return attacks_from<ROOK>(s) | attacks_from<BISHOP>(s);
478 inline Bitboard Position::checkers() const {
479 return st->checkersBB;
482 inline bool Position::is_check() const {
483 return st->checkersBB != EmptyBoardBB;
486 inline bool Position::pawn_is_passed(Color c, Square s) const {
487 return !(pieces(PAWN, opposite_color(c)) & passed_pawn_mask(c, s));
490 inline bool Position::square_is_weak(Square s, Color c) const {
491 return !(pieces(PAWN, opposite_color(c)) & attack_span_mask(c, s));
494 inline Key Position::get_key() const {
498 inline Key Position::get_exclusion_key() const {
499 return st->key ^ zobExclusion;
502 inline Key Position::get_pawn_key() const {
506 inline Key Position::get_material_key() const {
507 return st->materialKey;
510 inline Score Position::pst(Color c, PieceType pt, Square s) {
511 return PieceSquareTable[piece_of_color_and_type(c, pt)][s];
514 inline Score Position::pst_delta(Piece piece, Square from, Square to) {
515 return PieceSquareTable[piece][to] - PieceSquareTable[piece][from];
518 inline Score Position::value() const {
522 inline Value Position::non_pawn_material(Color c) const {
523 return st->npMaterial[c];
526 inline bool Position::move_is_passed_pawn_push(Move m) const {
528 Color c = side_to_move();
529 return piece_on(move_from(m)) == piece_of_color_and_type(c, PAWN)
530 && pawn_is_passed(c, move_to(m));
533 inline int Position::rule_50_counter() const {
538 inline bool Position::opposite_colored_bishops() const {
540 return piece_count(WHITE, BISHOP) == 1
541 && piece_count(BLACK, BISHOP) == 1
542 && square_color(piece_list(WHITE, BISHOP, 0)) != square_color(piece_list(BLACK, BISHOP, 0));
545 inline bool Position::has_pawn_on_7th(Color c) const {
547 return pieces(PAWN, c) & relative_rank_bb(c, RANK_7);
550 inline bool Position::move_is_capture(Move m) const {
552 // Move must not be MOVE_NONE !
553 return (m & (3 << 15)) ? !move_is_castle(m) : !square_is_empty(move_to(m));
556 inline bool Position::move_is_capture_or_promotion(Move m) const {
558 // Move must not be MOVE_NONE !
559 return (m & (0x1F << 12)) ? !move_is_castle(m) : !square_is_empty(move_to(m));
562 inline PieceType Position::captured_piece() const {
566 inline int Position::thread() const {
570 #endif // !defined(POSITION_H_INCLUDED)