2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2012 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 /// The checkInfo struct is initialized at c'tor time and keeps info used
30 /// to detect if a move gives check.
35 explicit CheckInfo(const Position&);
37 Bitboard dcCandidates;
44 /// The StateInfo struct stores information we need to restore a Position
45 /// object to its previous state when we retract a move. Whenever a move
46 /// is made on the board (by calling Position::do_move), an StateInfo object
47 /// must be passed as a parameter.
50 Key pawnKey, materialKey;
52 int castleRights, rule50, pliesFromNull;
58 PieceType capturedType;
63 /// The position data structure. A position consists of the following data:
65 /// * For each piece type, a bitboard representing the squares occupied
66 /// by pieces of that type.
67 /// * For each color, a bitboard representing the squares occupied by
68 /// pieces of that color.
69 /// * A bitboard of all occupied squares.
70 /// * A bitboard of all checking pieces.
71 /// * A 64-entry array of pieces, indexed by the squares of the board.
72 /// * The current side to move.
73 /// * Information about the castling rights for both sides.
74 /// * The initial files of the kings and both pairs of rooks. This is
75 /// used to implement the Chess960 castling rules.
76 /// * The en passant square (which is SQ_NONE if no en passant capture is
78 /// * The squares of the kings for both sides.
79 /// * Hash keys for the position itself, the current pawn structure, and
80 /// the current material situation.
81 /// * Hash keys for all previous positions in the game for detecting
83 /// * A counter for detecting 50 move rule draws.
87 // No copy c'tor or assignment operator allowed
88 Position(const Position&);
89 Position& operator=(const Position&);
93 Position(const Position& pos, int th) { copy(pos, th); }
94 Position(const std::string& fen, bool isChess960, int th);
97 void copy(const Position& pos, int th);
98 void from_fen(const std::string& fen, bool isChess960);
99 const std::string to_fen() const;
100 void print(Move m = MOVE_NONE) const;
102 // The piece on a given square
103 Piece piece_on(Square s) const;
104 Piece piece_moved(Move m) const;
105 bool square_is_empty(Square s) const;
108 Color side_to_move() const;
110 // Bitboard representation of the position
111 Bitboard empty_squares() const;
112 Bitboard occupied_squares() const;
113 Bitboard pieces(Color c) const;
114 Bitboard pieces(PieceType pt) const;
115 Bitboard pieces(PieceType pt, Color c) const;
116 Bitboard pieces(PieceType pt1, PieceType pt2) const;
117 Bitboard pieces(PieceType pt1, PieceType pt2, Color c) const;
119 // Number of pieces of each color and type
120 int piece_count(Color c, PieceType pt) const;
122 // The en passant square
123 Square ep_square() const;
125 // Current king position for each color
126 Square king_square(Color c) const;
129 bool can_castle(CastleRight f) const;
130 bool can_castle(Color c) const;
131 Square castle_rook_square(CastleRight f) const;
133 // Bitboards for pinned pieces and discovered check candidates
134 Bitboard discovered_check_candidates() const;
135 Bitboard pinned_pieces() const;
137 // Checking pieces and under check information
138 Bitboard checkers() const;
139 bool in_check() const;
142 const Square* piece_list(Color c, PieceType pt) const;
144 // Information about attacks to or from a given square
145 Bitboard attackers_to(Square s) const;
146 Bitboard attackers_to(Square s, Bitboard occ) const;
147 Bitboard attacks_from(Piece p, Square s) const;
148 static Bitboard attacks_from(Piece p, Square s, Bitboard occ);
149 template<PieceType> Bitboard attacks_from(Square s) const;
150 template<PieceType> Bitboard attacks_from(Square s, Color c) const;
152 // Properties of moves
153 bool move_gives_check(Move m, const CheckInfo& ci) const;
154 bool move_attacks_square(Move m, Square s) const;
155 bool pl_move_is_legal(Move m, Bitboard pinned) const;
156 bool is_pseudo_legal(const Move m) const;
157 bool is_capture(Move m) const;
158 bool is_capture_or_promotion(Move m) const;
159 bool is_passed_pawn_push(Move m) const;
161 // Piece captured with previous moves
162 PieceType captured_piece_type() const;
164 // Information about pawns
165 bool pawn_is_passed(Color c, Square s) const;
167 // Doing and undoing moves
168 void do_move(Move m, StateInfo& st);
169 void do_move(Move m, StateInfo& st, const CheckInfo& ci, bool moveIsCheck);
170 void undo_move(Move m);
171 template<bool Do> void do_null_move(StateInfo& st);
173 // Static exchange evaluation
174 int see(Move m) const;
175 int see_sign(Move m) const;
177 // Accessing hash keys
179 Key exclusion_key() const;
180 Key pawn_key() const;
181 Key material_key() const;
183 // Incremental evaluation
185 Value non_pawn_material(Color c) const;
186 Score pst_delta(Piece piece, Square from, Square to) const;
188 // Game termination checks
189 bool is_mate() const;
190 template<bool SkipRepetition> bool is_draw() const;
192 // Plies from start position to the beginning of search
193 int startpos_ply_counter() const;
195 // Other properties of the position
196 bool opposite_colored_bishops() const;
197 bool has_pawn_on_7th(Color c) const;
198 bool is_chess960() const;
200 // Current thread ID searching on the position
203 int64_t nodes_searched() const;
204 void set_nodes_searched(int64_t n);
206 // Position consistency check, for debugging
207 bool pos_is_ok(int* failedStep = NULL) const;
210 // Global initialization
215 // Initialization helper functions (used while setting up a position)
217 void put_piece(Piece p, Square s);
218 void set_castle_right(Square ksq, Square rsq);
219 bool move_is_legal(const Move m) const;
221 // Helper template functions
222 template<bool Do> void do_castle_move(Move m);
223 template<bool FindPinned> Bitboard hidden_checkers() const;
225 // Computing hash keys from scratch (for initialization and debugging)
226 Key compute_key() const;
227 Key compute_pawn_key() const;
228 Key compute_material_key() const;
230 // Computing incremental evaluation scores and material counts
231 Score pst(Piece p, Square s) const;
232 Score compute_value() const;
233 Value compute_non_pawn_material(Color c) const;
236 Piece board[64]; // [square]
239 Bitboard byTypeBB[8]; // [pieceType]
240 Bitboard byColorBB[2]; // [color]
244 int pieceCount[2][8]; // [color][pieceType]
247 Square pieceList[2][8][16]; // [color][pieceType][index]
248 int index[64]; // [square]
251 int castleRightsMask[64]; // [square]
252 Square castleRookSquare[16]; // [castleRight]
253 StateInfo startState;
262 static Score pieceSquareTable[16][64]; // [piece][square]
263 static Key zobrist[2][8][64]; // [color][pieceType][square]/[piece count]
264 static Key zobEp[64]; // [square]
265 static Key zobCastle[16]; // [castleRight]
266 static Key zobSideToMove;
267 static Key zobExclusion;
270 inline int64_t Position::nodes_searched() const {
274 inline void Position::set_nodes_searched(int64_t n) {
278 inline Piece Position::piece_on(Square s) const {
282 inline Piece Position::piece_moved(Move m) const {
283 return board[from_sq(m)];
286 inline bool Position::square_is_empty(Square s) const {
287 return board[s] == NO_PIECE;
290 inline Color Position::side_to_move() const {
294 inline Bitboard Position::occupied_squares() const {
298 inline Bitboard Position::empty_squares() const {
302 inline Bitboard Position::pieces(Color c) const {
306 inline Bitboard Position::pieces(PieceType pt) const {
310 inline Bitboard Position::pieces(PieceType pt, Color c) const {
311 return byTypeBB[pt] & byColorBB[c];
314 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2) const {
315 return byTypeBB[pt1] | byTypeBB[pt2];
318 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2, Color c) const {
319 return (byTypeBB[pt1] | byTypeBB[pt2]) & byColorBB[c];
322 inline int Position::piece_count(Color c, PieceType pt) const {
323 return pieceCount[c][pt];
326 inline const Square* Position::piece_list(Color c, PieceType pt) const {
327 return pieceList[c][pt];
330 inline Square Position::ep_square() const {
334 inline Square Position::king_square(Color c) const {
335 return pieceList[c][KING][0];
338 inline bool Position::can_castle(CastleRight f) const {
339 return st->castleRights & f;
342 inline bool Position::can_castle(Color c) const {
343 return st->castleRights & ((WHITE_OO | WHITE_OOO) << c);
346 inline Square Position::castle_rook_square(CastleRight f) const {
347 return castleRookSquare[f];
351 inline Bitboard Position::attacks_from<PAWN>(Square s, Color c) const {
352 return StepAttacksBB[make_piece(c, PAWN)][s];
355 template<PieceType Piece> // Knight and King and white pawns
356 inline Bitboard Position::attacks_from(Square s) const {
357 return StepAttacksBB[Piece][s];
361 inline Bitboard Position::attacks_from<BISHOP>(Square s) const {
362 return bishop_attacks_bb(s, occupied_squares());
366 inline Bitboard Position::attacks_from<ROOK>(Square s) const {
367 return rook_attacks_bb(s, occupied_squares());
371 inline Bitboard Position::attacks_from<QUEEN>(Square s) const {
372 return attacks_from<ROOK>(s) | attacks_from<BISHOP>(s);
375 inline Bitboard Position::attacks_from(Piece p, Square s) const {
376 return attacks_from(p, s, occupied_squares());
379 inline Bitboard Position::attackers_to(Square s) const {
380 return attackers_to(s, occupied_squares());
383 inline Bitboard Position::checkers() const {
384 return st->checkersBB;
387 inline bool Position::in_check() const {
388 return st->checkersBB != 0;
391 inline Bitboard Position::discovered_check_candidates() const {
392 return hidden_checkers<false>();
395 inline Bitboard Position::pinned_pieces() const {
396 return hidden_checkers<true>();
399 inline bool Position::pawn_is_passed(Color c, Square s) const {
400 return !(pieces(PAWN, flip(c)) & passed_pawn_mask(c, s));
403 inline Key Position::key() const {
407 inline Key Position::exclusion_key() const {
408 return st->key ^ zobExclusion;
411 inline Key Position::pawn_key() const {
415 inline Key Position::material_key() const {
416 return st->materialKey;
419 inline Score Position::pst(Piece p, Square s) const {
420 return pieceSquareTable[p][s];
423 inline Score Position::pst_delta(Piece piece, Square from, Square to) const {
424 return pieceSquareTable[piece][to] - pieceSquareTable[piece][from];
427 inline Score Position::value() const {
431 inline Value Position::non_pawn_material(Color c) const {
432 return st->npMaterial[c];
435 inline bool Position::is_passed_pawn_push(Move m) const {
437 return board[from_sq(m)] == make_piece(sideToMove, PAWN)
438 && pawn_is_passed(sideToMove, to_sq(m));
441 inline int Position::startpos_ply_counter() const {
442 return startPosPly + st->pliesFromNull; // HACK
445 inline bool Position::opposite_colored_bishops() const {
447 return pieceCount[WHITE][BISHOP] == 1
448 && pieceCount[BLACK][BISHOP] == 1
449 && opposite_colors(pieceList[WHITE][BISHOP][0], pieceList[BLACK][BISHOP][0]);
452 inline bool Position::has_pawn_on_7th(Color c) const {
453 return pieces(PAWN, c) & rank_bb(relative_rank(c, RANK_7));
456 inline bool Position::is_chess960() const {
460 inline bool Position::is_capture_or_promotion(Move m) const {
463 return is_special(m) ? !is_castle(m) : !square_is_empty(to_sq(m));
466 inline bool Position::is_capture(Move m) const {
468 // Note that castle is coded as "king captures the rook"
470 return (!square_is_empty(to_sq(m)) && !is_castle(m)) || is_enpassant(m);
473 inline PieceType Position::captured_piece_type() const {
474 return st->capturedType;
477 inline int Position::thread() const {
481 #endif // !defined(POSITION_H_INCLUDED)