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
30 /// The checkInfo struct is initialized at c'tor time and keeps info used
31 /// to detect if a move gives check.
37 explicit CheckInfo(const Position&);
39 Bitboard dcCandidates;
41 Bitboard checkSq[PIECE_TYPE_NB];
46 /// The StateInfo struct stores information we need to restore a Position
47 /// object to its previous state when we retract a move. Whenever a move
48 /// is made on the board (by calling Position::do_move), a StateInfo object
49 /// must be passed as a parameter.
52 Key pawnKey, materialKey;
53 Value npMaterial[COLOR_NB];
54 int castleRights, rule50, pliesFromNull;
60 PieceType capturedType;
65 /// When making a move the current StateInfo up to 'key' excluded is copied to
66 /// the new one. Here we calculate the quad words (64bits) needed to be copied.
67 const size_t StateCopySize64 = offsetof(StateInfo, key) / sizeof(uint64_t) + 1;
70 /// The position data structure. A position consists of the following data:
72 /// * For each piece type, a bitboard representing the squares occupied
73 /// by pieces of that type.
74 /// * For each color, a bitboard representing the squares occupied by
75 /// pieces of that color.
76 /// * A bitboard of all occupied squares.
77 /// * A bitboard of all checking pieces.
78 /// * A 64-entry array of pieces, indexed by the squares of the board.
79 /// * The current side to move.
80 /// * Information about the castling rights for both sides.
81 /// * The initial files of the kings and both pairs of rooks. This is
82 /// used to implement the Chess960 castling rules.
83 /// * The en passant square (which is SQ_NONE if no en passant capture is
85 /// * The squares of the kings for both sides.
86 /// * Hash keys for the position itself, the current pawn structure, and
87 /// the current material situation.
88 /// * Hash keys for all previous positions in the game for detecting
90 /// * A counter for detecting 50 move rule draws.
95 Position(const Position& p, Thread* t) { *this = p; thisThread = t; }
96 Position(const std::string& f, bool c960, Thread* t) { from_fen(f, c960, t); }
97 Position& operator=(const Position&);
100 void from_fen(const std::string& fen, bool isChess960, Thread* th);
101 const std::string to_fen() const;
102 void print(Move m = MOVE_NONE) const;
104 // Position representation
105 Bitboard pieces() const;
106 Bitboard pieces(PieceType pt) const;
107 Bitboard pieces(PieceType pt1, PieceType pt2) const;
108 Bitboard pieces(Color c) const;
109 Bitboard pieces(Color c, PieceType pt) const;
110 Bitboard pieces(Color c, PieceType pt1, PieceType pt2) const;
111 Piece piece_on(Square s) const;
112 Square king_square(Color c) const;
113 Square ep_square() const;
114 bool is_empty(Square s) const;
115 const Square* piece_list(Color c, PieceType pt) const;
116 int piece_count(Color c, PieceType pt) const;
119 int can_castle(CastleRight f) const;
120 int can_castle(Color c) const;
121 bool castle_impeded(Color c, CastlingSide s) const;
122 Square castle_rook_square(Color c, CastlingSide s) const;
125 bool in_check() const;
126 Bitboard checkers() const;
127 Bitboard discovered_check_candidates() const;
128 Bitboard pinned_pieces() const;
130 // Attacks to/from a given square
131 Bitboard attackers_to(Square s) const;
132 Bitboard attackers_to(Square s, Bitboard occ) const;
133 Bitboard attacks_from(Piece p, Square s) const;
134 static Bitboard attacks_from(Piece p, Square s, Bitboard occ);
135 template<PieceType> Bitboard attacks_from(Square s) const;
136 template<PieceType> Bitboard attacks_from(Square s, Color c) const;
138 // Properties of moves
139 bool move_gives_check(Move m, const CheckInfo& ci) const;
140 bool move_is_legal(const Move m) const;
141 bool pl_move_is_legal(Move m, Bitboard pinned) const;
142 bool is_pseudo_legal(const Move m) const;
143 bool is_capture(Move m) const;
144 bool is_capture_or_promotion(Move m) const;
145 bool is_passed_pawn_push(Move m) const;
146 Piece piece_moved(Move m) const;
147 PieceType captured_piece_type() const;
150 bool pawn_is_passed(Color c, Square s) const;
151 bool pawn_on_7th(Color c) const;
152 bool opposite_bishops() const;
153 bool bishop_pair(Color c) const;
155 // Doing and undoing moves
156 void do_move(Move m, StateInfo& st);
157 void do_move(Move m, StateInfo& st, const CheckInfo& ci, bool moveIsCheck);
158 void undo_move(Move m);
159 template<bool Do> void do_null_move(StateInfo& st);
161 // Static exchange evaluation
162 int see(Move m) const;
163 int see_sign(Move m) const;
165 // Accessing hash keys
167 Key exclusion_key() const;
168 Key pawn_key() const;
169 Key material_key() const;
171 // Incremental piece-square evaluation
172 Score psq_score() const;
173 Score psq_delta(Piece p, Square from, Square to) const;
174 Value non_pawn_material(Color c) const;
176 // Other properties of the position
177 Color side_to_move() const;
178 int startpos_ply_counter() const;
179 bool is_chess960() const;
180 Thread* this_thread() const;
181 int64_t nodes_searched() const;
182 void set_nodes_searched(int64_t n);
183 template<bool CheckRepetition, bool CheckThreeFold> bool is_draw() const;
185 // Position consistency check, for debugging
186 bool pos_is_ok(int* failedStep = NULL) const;
190 // Initialization helpers (used while setting up a position)
192 void put_piece(Piece p, Square s);
193 void set_castle_right(Color c, Square rfrom);
195 // Helper template functions
196 template<bool Do> void do_castle_move(Move m);
197 template<bool FindPinned> Bitboard hidden_checkers() const;
199 // Computing hash keys from scratch (for initialization and debugging)
200 Key compute_key() const;
201 Key compute_pawn_key() const;
202 Key compute_material_key() const;
204 // Computing incremental evaluation scores and material counts
205 Score compute_psq_score() const;
206 Value compute_non_pawn_material(Color c) const;
209 Piece board[SQUARE_NB];
210 Bitboard byTypeBB[PIECE_TYPE_NB];
211 Bitboard byColorBB[COLOR_NB];
212 int pieceCount[COLOR_NB][PIECE_TYPE_NB];
213 Square pieceList[COLOR_NB][PIECE_TYPE_NB][16];
214 int index[SQUARE_NB];
217 int castleRightsMask[SQUARE_NB];
218 Square castleRookSquare[COLOR_NB][CASTLING_SIDE_NB];
219 Bitboard castlePath[COLOR_NB][CASTLING_SIDE_NB];
220 StateInfo startState;
229 inline int64_t Position::nodes_searched() const {
233 inline void Position::set_nodes_searched(int64_t n) {
237 inline Piece Position::piece_on(Square s) const {
241 inline Piece Position::piece_moved(Move m) const {
242 return board[from_sq(m)];
245 inline bool Position::is_empty(Square s) const {
246 return board[s] == NO_PIECE;
249 inline Color Position::side_to_move() const {
253 inline Bitboard Position::pieces() const {
254 return byTypeBB[ALL_PIECES];
257 inline Bitboard Position::pieces(PieceType pt) const {
261 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2) const {
262 return byTypeBB[pt1] | byTypeBB[pt2];
265 inline Bitboard Position::pieces(Color c) const {
269 inline Bitboard Position::pieces(Color c, PieceType pt) const {
270 return byColorBB[c] & byTypeBB[pt];
273 inline Bitboard Position::pieces(Color c, PieceType pt1, PieceType pt2) const {
274 return byColorBB[c] & (byTypeBB[pt1] | byTypeBB[pt2]);
277 inline int Position::piece_count(Color c, PieceType pt) const {
278 return pieceCount[c][pt];
281 inline const Square* Position::piece_list(Color c, PieceType pt) const {
282 return pieceList[c][pt];
285 inline Square Position::ep_square() const {
289 inline Square Position::king_square(Color c) const {
290 return pieceList[c][KING][0];
293 inline int Position::can_castle(CastleRight f) const {
294 return st->castleRights & f;
297 inline int Position::can_castle(Color c) const {
298 return st->castleRights & ((WHITE_OO | WHITE_OOO) << (2 * c));
301 inline bool Position::castle_impeded(Color c, CastlingSide s) const {
302 return byTypeBB[ALL_PIECES] & castlePath[c][s];
305 inline Square Position::castle_rook_square(Color c, CastlingSide s) const {
306 return castleRookSquare[c][s];
309 template<PieceType Pt>
310 inline Bitboard Position::attacks_from(Square s) const {
312 return Pt == BISHOP || Pt == ROOK ? attacks_bb<Pt>(s, pieces())
313 : Pt == QUEEN ? attacks_from<ROOK>(s) | attacks_from<BISHOP>(s)
314 : StepAttacksBB[Pt][s];
318 inline Bitboard Position::attacks_from<PAWN>(Square s, Color c) const {
319 return StepAttacksBB[make_piece(c, PAWN)][s];
322 inline Bitboard Position::attacks_from(Piece p, Square s) const {
323 return attacks_from(p, s, byTypeBB[ALL_PIECES]);
326 inline Bitboard Position::attackers_to(Square s) const {
327 return attackers_to(s, byTypeBB[ALL_PIECES]);
330 inline Bitboard Position::checkers() const {
331 return st->checkersBB;
334 inline bool Position::in_check() const {
335 return st->checkersBB != 0;
338 inline Bitboard Position::discovered_check_candidates() const {
339 return hidden_checkers<false>();
342 inline Bitboard Position::pinned_pieces() const {
343 return hidden_checkers<true>();
346 inline bool Position::pawn_is_passed(Color c, Square s) const {
347 return !(pieces(~c, PAWN) & passed_pawn_mask(c, s));
350 inline Key Position::key() const {
354 inline Key Position::exclusion_key() const {
355 return st->key ^ Zobrist::exclusion;
358 inline Key Position::pawn_key() const {
362 inline Key Position::material_key() const {
363 return st->materialKey;
366 inline Score Position::psq_delta(Piece p, Square from, Square to) const {
367 return pieceSquareTable[p][to] - pieceSquareTable[p][from];
370 inline Score Position::psq_score() const {
374 inline Value Position::non_pawn_material(Color c) const {
375 return st->npMaterial[c];
378 inline bool Position::is_passed_pawn_push(Move m) const {
380 return type_of(piece_moved(m)) == PAWN
381 && pawn_is_passed(sideToMove, to_sq(m));
384 inline int Position::startpos_ply_counter() const {
385 return startPosPly + st->pliesFromNull; // HACK
388 inline bool Position::opposite_bishops() const {
390 return pieceCount[WHITE][BISHOP] == 1
391 && pieceCount[BLACK][BISHOP] == 1
392 && opposite_colors(pieceList[WHITE][BISHOP][0], pieceList[BLACK][BISHOP][0]);
395 inline bool Position::bishop_pair(Color c) const {
397 return pieceCount[c][BISHOP] >= 2
398 && opposite_colors(pieceList[c][BISHOP][0], pieceList[c][BISHOP][1]);
401 inline bool Position::pawn_on_7th(Color c) const {
402 return pieces(c, PAWN) & rank_bb(relative_rank(c, RANK_7));
405 inline bool Position::is_chess960() const {
409 inline bool Position::is_capture_or_promotion(Move m) const {
412 return type_of(m) ? type_of(m) != CASTLE : !is_empty(to_sq(m));
415 inline bool Position::is_capture(Move m) const {
417 // Note that castle is coded as "king captures the rook"
419 return (!is_empty(to_sq(m)) && type_of(m) != CASTLE) || type_of(m) == ENPASSANT;
422 inline PieceType Position::captured_piece_type() const {
423 return st->capturedType;
426 inline Thread* Position::this_thread() const {
430 #endif // !defined(POSITION_H_INCLUDED)