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) { set(f, c960, t); }
97 Position& operator=(const Position&);
100 void set(const std::string& fen, bool isChess960, Thread* th);
101 const std::string fen() const;
102 const std::string pretty(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 Bitboard checkers() const;
126 Bitboard discovered_check_candidates() const;
127 Bitboard pinned_pieces() const;
129 // Attacks to/from a given square
130 Bitboard attackers_to(Square s) const;
131 Bitboard attackers_to(Square s, Bitboard occ) const;
132 Bitboard attacks_from(Piece p, Square s) const;
133 static Bitboard attacks_from(Piece p, Square s, Bitboard occ);
134 template<PieceType> Bitboard attacks_from(Square s) const;
135 template<PieceType> Bitboard attacks_from(Square s, Color c) const;
137 // Properties of moves
138 bool move_gives_check(Move m, const CheckInfo& ci) const;
139 bool pl_move_is_legal(Move m, Bitboard pinned) const;
140 bool is_pseudo_legal(const Move m) const;
141 bool is_capture(Move m) const;
142 bool is_capture_or_promotion(Move m) const;
143 bool is_passed_pawn_push(Move m) const;
144 Piece piece_moved(Move m) const;
145 PieceType captured_piece_type() const;
148 bool pawn_is_passed(Color c, Square s) const;
149 bool pawn_on_7th(Color c) const;
150 bool opposite_bishops() const;
151 bool bishop_pair(Color c) const;
153 // Doing and undoing moves
154 void do_move(Move m, StateInfo& st);
155 void do_move(Move m, StateInfo& st, const CheckInfo& ci, bool moveIsCheck);
156 void undo_move(Move m);
157 template<bool Do> void do_null_move(StateInfo& st);
159 // Static exchange evaluation
160 int see(Move m) const;
161 int see_sign(Move m) const;
163 // Accessing hash keys
165 Key exclusion_key() const;
166 Key pawn_key() const;
167 Key material_key() const;
169 // Incremental piece-square evaluation
170 Score psq_score() const;
171 Score psq_delta(Piece p, Square from, Square to) const;
172 Value non_pawn_material(Color c) const;
174 // Other properties of the position
175 Color side_to_move() const;
176 int startpos_ply_counter() const;
177 bool is_chess960() const;
178 Thread* this_thread() const;
179 int64_t nodes_searched() const;
180 void set_nodes_searched(int64_t n);
181 template<bool CheckRepetition, bool CheckThreeFold> bool is_draw() const;
183 // Position consistency check, for debugging
184 bool pos_is_ok(int* failedStep = NULL) const;
188 // Initialization helpers (used while setting up a position)
190 void put_piece(Piece p, Square s);
191 void set_castle_right(Color c, Square rfrom);
193 // Helper template functions
194 template<bool Do> void do_castle_move(Move m);
195 template<bool FindPinned> Bitboard hidden_checkers() const;
197 // Computing hash keys from scratch (for initialization and debugging)
198 Key compute_key() const;
199 Key compute_pawn_key() const;
200 Key compute_material_key() const;
202 // Computing incremental evaluation scores and material counts
203 Score compute_psq_score() const;
204 Value compute_non_pawn_material(Color c) const;
207 Piece board[SQUARE_NB];
208 Bitboard byTypeBB[PIECE_TYPE_NB];
209 Bitboard byColorBB[COLOR_NB];
210 int pieceCount[COLOR_NB][PIECE_TYPE_NB];
211 Square pieceList[COLOR_NB][PIECE_TYPE_NB][16];
212 int index[SQUARE_NB];
215 int castleRightsMask[SQUARE_NB];
216 Square castleRookSquare[COLOR_NB][CASTLING_SIDE_NB];
217 Bitboard castlePath[COLOR_NB][CASTLING_SIDE_NB];
218 StateInfo startState;
227 inline int64_t Position::nodes_searched() const {
231 inline void Position::set_nodes_searched(int64_t n) {
235 inline Piece Position::piece_on(Square s) const {
239 inline Piece Position::piece_moved(Move m) const {
240 return board[from_sq(m)];
243 inline bool Position::is_empty(Square s) const {
244 return board[s] == NO_PIECE;
247 inline Color Position::side_to_move() const {
251 inline Bitboard Position::pieces() const {
252 return byTypeBB[ALL_PIECES];
255 inline Bitboard Position::pieces(PieceType pt) const {
259 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2) const {
260 return byTypeBB[pt1] | byTypeBB[pt2];
263 inline Bitboard Position::pieces(Color c) const {
267 inline Bitboard Position::pieces(Color c, PieceType pt) const {
268 return byColorBB[c] & byTypeBB[pt];
271 inline Bitboard Position::pieces(Color c, PieceType pt1, PieceType pt2) const {
272 return byColorBB[c] & (byTypeBB[pt1] | byTypeBB[pt2]);
275 inline int Position::piece_count(Color c, PieceType pt) const {
276 return pieceCount[c][pt];
279 inline const Square* Position::piece_list(Color c, PieceType pt) const {
280 return pieceList[c][pt];
283 inline Square Position::ep_square() const {
287 inline Square Position::king_square(Color c) const {
288 return pieceList[c][KING][0];
291 inline int Position::can_castle(CastleRight f) const {
292 return st->castleRights & f;
295 inline int Position::can_castle(Color c) const {
296 return st->castleRights & ((WHITE_OO | WHITE_OOO) << (2 * c));
299 inline bool Position::castle_impeded(Color c, CastlingSide s) const {
300 return byTypeBB[ALL_PIECES] & castlePath[c][s];
303 inline Square Position::castle_rook_square(Color c, CastlingSide s) const {
304 return castleRookSquare[c][s];
307 template<PieceType Pt>
308 inline Bitboard Position::attacks_from(Square s) const {
310 return Pt == BISHOP || Pt == ROOK ? attacks_bb<Pt>(s, pieces())
311 : Pt == QUEEN ? attacks_from<ROOK>(s) | attacks_from<BISHOP>(s)
312 : StepAttacksBB[Pt][s];
316 inline Bitboard Position::attacks_from<PAWN>(Square s, Color c) const {
317 return StepAttacksBB[make_piece(c, PAWN)][s];
320 inline Bitboard Position::attacks_from(Piece p, Square s) const {
321 return attacks_from(p, s, byTypeBB[ALL_PIECES]);
324 inline Bitboard Position::attackers_to(Square s) const {
325 return attackers_to(s, byTypeBB[ALL_PIECES]);
328 inline Bitboard Position::checkers() const {
329 return st->checkersBB;
332 inline Bitboard Position::discovered_check_candidates() const {
333 return hidden_checkers<false>();
336 inline Bitboard Position::pinned_pieces() const {
337 return hidden_checkers<true>();
340 inline bool Position::pawn_is_passed(Color c, Square s) const {
341 return !(pieces(~c, PAWN) & passed_pawn_mask(c, s));
344 inline Key Position::key() const {
348 inline Key Position::exclusion_key() const {
349 return st->key ^ Zobrist::exclusion;
352 inline Key Position::pawn_key() const {
356 inline Key Position::material_key() const {
357 return st->materialKey;
360 inline Score Position::psq_delta(Piece p, Square from, Square to) const {
361 return pieceSquareTable[p][to] - pieceSquareTable[p][from];
364 inline Score Position::psq_score() const {
368 inline Value Position::non_pawn_material(Color c) const {
369 return st->npMaterial[c];
372 inline bool Position::is_passed_pawn_push(Move m) const {
374 return type_of(piece_moved(m)) == PAWN
375 && pawn_is_passed(sideToMove, to_sq(m));
378 inline int Position::startpos_ply_counter() const {
379 return startPosPly + st->pliesFromNull; // HACK
382 inline bool Position::opposite_bishops() const {
384 return pieceCount[WHITE][BISHOP] == 1
385 && pieceCount[BLACK][BISHOP] == 1
386 && opposite_colors(pieceList[WHITE][BISHOP][0], pieceList[BLACK][BISHOP][0]);
389 inline bool Position::bishop_pair(Color c) const {
391 return pieceCount[c][BISHOP] >= 2
392 && opposite_colors(pieceList[c][BISHOP][0], pieceList[c][BISHOP][1]);
395 inline bool Position::pawn_on_7th(Color c) const {
396 return pieces(c, PAWN) & rank_bb(relative_rank(c, RANK_7));
399 inline bool Position::is_chess960() const {
403 inline bool Position::is_capture_or_promotion(Move m) const {
406 return type_of(m) ? type_of(m) != CASTLE : !is_empty(to_sq(m));
409 inline bool Position::is_capture(Move m) const {
411 // Note that castle is coded as "king captures the rook"
413 return (!is_empty(to_sq(m)) && type_of(m) != CASTLE) || type_of(m) == ENPASSANT;
416 inline PieceType Position::captured_piece_type() const {
417 return st->capturedType;
420 inline Thread* Position::this_thread() const {
424 #endif // !defined(POSITION_H_INCLUDED)