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/>.
20 #if !defined(POSITION_H_INCLUDED)
21 #define POSITION_H_INCLUDED
29 /// Maximum number of plies per game (220 should be enough, because the
30 /// maximum search depth is 100, and during position setup we reset the
31 /// move counter for every non-reversible move).
32 const int MaxGameLength = 220;
35 /// The checkInfo struct is initialized at c'tor time and keeps info used
36 /// to detect if a move gives check.
40 explicit CheckInfo(const Position&);
42 Bitboard dcCandidates;
48 /// The StateInfo struct stores information we need to restore a Position
49 /// object to its previous state when we retract a move. Whenever a move
50 /// is made on the board (by calling Position::do_move), an StateInfo object
51 /// must be passed as a parameter.
55 Key pawnKey, materialKey;
56 int castleRights, rule50, gamePly, pliesFromNull;
63 PieceType capturedType;
68 /// The position data structure. A position consists of the following data:
70 /// * For each piece type, a bitboard representing the squares occupied
71 /// by pieces of that type.
72 /// * For each color, a bitboard representing the squares occupied by
73 /// pieces of that color.
74 /// * A bitboard of all occupied squares.
75 /// * A bitboard of all checking pieces.
76 /// * A 64-entry array of pieces, indexed by the squares of the board.
77 /// * The current side to move.
78 /// * Information about the castling rights for both sides.
79 /// * The initial files of the kings and both pairs of rooks. This is
80 /// used to implement the Chess960 castling rules.
81 /// * The en passant square (which is SQ_NONE if no en passant capture is
83 /// * The squares of the kings for both sides.
84 /// * Hash keys for the position itself, the current pawn structure, and
85 /// the current material situation.
86 /// * Hash keys for all previous positions in the game for detecting
88 /// * A counter for detecting 50 move rule draws.
92 // No defaul, copy c'tor or assignment allowed, default c'tor will not be
93 // generated anyhow because of user-defined c'tors.
94 Position(const Position&);
95 Position& operator=(const Position&);
98 Position(const Position& pos, int threadID);
99 Position(const std::string& fen, bool isChess960, int threadID);
102 void from_fen(const std::string& fen, bool isChess960);
103 const std::string to_fen() const;
104 void print(Move m = MOVE_NONE) const;
106 // The piece on a given square
107 Piece piece_on(Square s) const;
108 bool square_is_empty(Square s) const;
111 Color side_to_move() const;
113 // Bitboard representation of the position
114 Bitboard empty_squares() const;
115 Bitboard occupied_squares() const;
116 Bitboard pieces(Color c) const;
117 Bitboard pieces(PieceType pt) const;
118 Bitboard pieces(PieceType pt, Color c) const;
119 Bitboard pieces(PieceType pt1, PieceType pt2) const;
120 Bitboard pieces(PieceType pt1, PieceType pt2, Color c) const;
122 // Number of pieces of each color and type
123 int piece_count(Color c, PieceType pt) const;
125 // The en passant square
126 Square ep_square() const;
128 // Current king position for each color
129 Square king_square(Color c) const;
132 bool can_castle(CastleRight f) const;
133 bool can_castle(Color c) const;
134 Square castle_rook_square(CastleRight f) const;
136 // Bitboards for pinned pieces and discovered check candidates
137 Bitboard discovered_check_candidates() const;
138 Bitboard pinned_pieces() const;
140 // Checking pieces and under check information
141 Bitboard checkers() const;
142 bool in_check() const;
145 const Square* piece_list(Color c, PieceType pt) const;
147 // Information about attacks to or from a given square
148 Bitboard attackers_to(Square s) const;
149 Bitboard attackers_to(Square s, Bitboard occ) const;
150 Bitboard attacks_from(Piece p, Square s) const;
151 static Bitboard attacks_from(Piece p, Square s, Bitboard occ);
152 template<PieceType> Bitboard attacks_from(Square s) const;
153 template<PieceType> Bitboard attacks_from(Square s, Color c) const;
155 // Properties of moves
156 bool pl_move_is_legal(Move m, Bitboard pinned) const;
157 bool move_is_pl(const Move m) const;
158 bool move_gives_check(Move m, const CheckInfo& ci) const;
159 bool move_is_capture(Move m) const;
160 bool move_is_capture_or_promotion(Move m) const;
161 bool move_is_passed_pawn_push(Move m) const;
162 bool move_attacks_square(Move m, Square s) const;
164 // Piece captured with previous moves
165 PieceType captured_piece_type() const;
167 // Information about pawns
168 bool pawn_is_passed(Color c, Square s) const;
170 // Doing and undoing moves
171 void do_setup_move(Move m);
172 void do_move(Move m, StateInfo& st);
173 void do_move(Move m, StateInfo& st, const CheckInfo& ci, bool moveIsCheck);
174 void undo_move(Move m);
175 void do_null_move(StateInfo& st);
176 void undo_null_move();
178 // Static exchange evaluation
179 int see(Move m) const;
180 int see_sign(Move m) const;
182 // Accessing hash keys
184 Key get_exclusion_key() const;
185 Key get_pawn_key() const;
186 Key get_material_key() const;
188 // Incremental evaluation
190 Value non_pawn_material(Color c) const;
191 Score pst_delta(Piece piece, Square from, Square to) const;
193 // Game termination checks
194 bool is_mate() const;
195 template<bool SkipRepetition> bool is_draw() const;
197 // Number of plies from starting position
198 int startpos_ply_counter() const;
200 // Other properties of the position
201 bool opposite_colored_bishops() const;
202 bool has_pawn_on_7th(Color c) const;
203 bool is_chess960() const;
205 // Current thread ID searching on the position
208 int64_t nodes_searched() const;
209 void set_nodes_searched(int64_t n);
211 // Position consistency check, for debugging
212 bool is_ok(int* failedStep = NULL) const;
215 // Global initialization
220 // Initialization helper functions (used while setting up a position)
223 void put_piece(Piece p, Square s);
224 void set_castle(int f, Square ksq, Square rsq);
225 void set_castling_rights(char token);
226 bool move_is_legal(const Move m) const;
228 // Helper functions for doing and undoing moves
229 void do_capture_move(Key& key, PieceType capture, Color them, Square to, bool ep);
230 void do_castle_move(Move m);
231 void undo_castle_move(Move m);
233 template<bool FindPinned>
234 Bitboard hidden_checkers() const;
236 // Computing hash keys from scratch (for initialization and debugging)
237 Key compute_key() const;
238 Key compute_pawn_key() const;
239 Key compute_material_key() const;
241 // Computing incremental evaluation scores and material counts
242 Score pst(Piece p, Square s) const;
243 Score compute_value() const;
244 Value compute_non_pawn_material(Color c) const;
247 Piece board[64]; // [square]
250 Bitboard byTypeBB[8]; // [pieceType]
251 Bitboard byColorBB[2]; // [color]
254 int pieceCount[2][8]; // [color][pieceType]
257 Square pieceList[2][8][16]; // [color][pieceType][index]
258 int index[64]; // [square]
261 Key history[MaxGameLength];
262 int castleRightsMask[64]; // [square]
263 Square castleRookSquare[16]; // [castleRight]
264 StateInfo startState;
273 static Score pieceSquareTable[16][64]; // [piece][square]
274 static Key zobrist[2][8][64]; // [color][pieceType][square]
275 static Key zobEp[64]; // [square]
276 static Key zobCastle[16]; // [castleRight]
277 static Key zobSideToMove;
278 static Key zobExclusion;
281 inline int64_t Position::nodes_searched() const {
285 inline void Position::set_nodes_searched(int64_t n) {
289 inline Piece Position::piece_on(Square s) const {
293 inline bool Position::square_is_empty(Square s) const {
294 return piece_on(s) == PIECE_NONE;
297 inline Color Position::side_to_move() const {
301 inline Bitboard Position::occupied_squares() const {
305 inline Bitboard Position::empty_squares() const {
306 return ~occupied_squares();
309 inline Bitboard Position::pieces(Color c) const {
313 inline Bitboard Position::pieces(PieceType pt) const {
317 inline Bitboard Position::pieces(PieceType pt, Color c) const {
318 return byTypeBB[pt] & byColorBB[c];
321 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2) const {
322 return byTypeBB[pt1] | byTypeBB[pt2];
325 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2, Color c) const {
326 return (byTypeBB[pt1] | byTypeBB[pt2]) & byColorBB[c];
329 inline int Position::piece_count(Color c, PieceType pt) const {
330 return pieceCount[c][pt];
333 inline const Square* Position::piece_list(Color c, PieceType pt) const {
334 return pieceList[c][pt];
337 inline Square Position::ep_square() const {
341 inline Square Position::king_square(Color c) const {
342 return pieceList[c][KING][0];
345 inline bool Position::can_castle(CastleRight f) const {
346 return st->castleRights & f;
349 inline bool Position::can_castle(Color c) const {
350 return st->castleRights & ((WHITE_OO | WHITE_OOO) << c);
353 inline Square Position::castle_rook_square(CastleRight f) const {
354 return castleRookSquare[f];
358 inline Bitboard Position::attacks_from<PAWN>(Square s, Color c) const {
359 return StepAttacksBB[make_piece(c, PAWN)][s];
362 template<PieceType Piece> // Knight and King and white pawns
363 inline Bitboard Position::attacks_from(Square s) const {
364 return StepAttacksBB[Piece][s];
368 inline Bitboard Position::attacks_from<BISHOP>(Square s) const {
369 return bishop_attacks_bb(s, occupied_squares());
373 inline Bitboard Position::attacks_from<ROOK>(Square s) const {
374 return rook_attacks_bb(s, occupied_squares());
378 inline Bitboard Position::attacks_from<QUEEN>(Square s) const {
379 return attacks_from<ROOK>(s) | attacks_from<BISHOP>(s);
382 inline Bitboard Position::checkers() const {
383 return st->checkersBB;
386 inline bool Position::in_check() const {
387 return st->checkersBB != EmptyBoardBB;
390 inline bool Position::pawn_is_passed(Color c, Square s) const {
391 return !(pieces(PAWN, opposite_color(c)) & passed_pawn_mask(c, s));
394 inline Key Position::get_key() const {
398 inline Key Position::get_exclusion_key() const {
399 return st->key ^ zobExclusion;
402 inline Key Position::get_pawn_key() const {
406 inline Key Position::get_material_key() const {
407 return st->materialKey;
410 inline Score Position::pst(Piece p, Square s) const {
411 return pieceSquareTable[p][s];
414 inline Score Position::pst_delta(Piece piece, Square from, Square to) const {
415 return pieceSquareTable[piece][to] - pieceSquareTable[piece][from];
418 inline Score Position::value() const {
422 inline Value Position::non_pawn_material(Color c) const {
423 return st->npMaterial[c];
426 inline bool Position::move_is_passed_pawn_push(Move m) const {
428 Color c = side_to_move();
429 return piece_on(move_from(m)) == make_piece(c, PAWN)
430 && pawn_is_passed(c, move_to(m));
433 inline int Position::startpos_ply_counter() const {
434 return Max(2 * (fullMoves - 1), 0) + int(sideToMove == BLACK);
437 inline bool Position::opposite_colored_bishops() const {
439 return piece_count(WHITE, BISHOP) == 1
440 && piece_count(BLACK, BISHOP) == 1
441 && opposite_color_squares(piece_list(WHITE, BISHOP)[0], piece_list(BLACK, BISHOP)[0]);
444 inline bool Position::has_pawn_on_7th(Color c) const {
445 return pieces(PAWN, c) & rank_bb(relative_rank(c, RANK_7));
448 inline bool Position::is_chess960() const {
452 inline bool Position::move_is_capture_or_promotion(Move m) const {
454 assert(move_is_ok(m));
455 return move_is_special(m) ? !move_is_castle(m) : !square_is_empty(move_to(m));
458 inline bool Position::move_is_capture(Move m) const {
460 // Note that castle is coded as "king captures the rook"
461 assert(move_is_ok(m));
462 return (!square_is_empty(move_to(m)) && !move_is_castle(m)) || move_is_ep(m);
465 inline PieceType Position::captured_piece_type() const {
466 return st->capturedType;
469 inline int Position::thread() const {
473 #endif // !defined(POSITION_H_INCLUDED)