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_attacks_square(Move m, Square s) const;
141 bool move_is_legal(const Move m) const;
142 bool pl_move_is_legal(Move m, Bitboard pinned) const;
143 bool is_pseudo_legal(const Move m) const;
144 bool is_capture(Move m) const;
145 bool is_capture_or_promotion(Move m) const;
146 bool is_passed_pawn_push(Move m) const;
147 Piece piece_moved(Move m) const;
148 PieceType captured_piece_type() const;
151 bool pawn_is_passed(Color c, Square s) const;
152 bool pawn_on_7th(Color c) const;
153 bool opposite_bishops() const;
154 bool bishop_pair(Color c) const;
156 // Doing and undoing moves
157 void do_move(Move m, StateInfo& st);
158 void do_move(Move m, StateInfo& st, const CheckInfo& ci, bool moveIsCheck);
159 void undo_move(Move m);
160 template<bool Do> void do_null_move(StateInfo& st);
162 // Static exchange evaluation
163 int see(Move m) const;
164 int see_sign(Move m) const;
166 // Accessing hash keys
168 Key exclusion_key() const;
169 Key pawn_key() const;
170 Key material_key() const;
172 // Incremental piece-square evaluation
173 Score psq_score() const;
174 Score psq_delta(Piece p, Square from, Square to) const;
175 Value non_pawn_material(Color c) const;
177 // Other properties of the position
178 Color side_to_move() const;
179 int startpos_ply_counter() const;
180 bool is_chess960() const;
181 Thread* this_thread() const;
182 int64_t nodes_searched() const;
183 void set_nodes_searched(int64_t n);
184 template<bool CheckRepetition, bool CheckThreeFold> bool is_draw() const;
186 // Position consistency check, for debugging
187 bool pos_is_ok(int* failedStep = NULL) const;
191 // Initialization helpers (used while setting up a position)
193 void put_piece(Piece p, Square s);
194 void set_castle_right(Color c, Square rfrom);
196 // Helper template functions
197 template<bool Do> void do_castle_move(Move m);
198 template<bool FindPinned> Bitboard hidden_checkers() const;
200 // Computing hash keys from scratch (for initialization and debugging)
201 Key compute_key() const;
202 Key compute_pawn_key() const;
203 Key compute_material_key() const;
205 // Computing incremental evaluation scores and material counts
206 Score compute_psq_score() const;
207 Value compute_non_pawn_material(Color c) const;
210 Piece board[SQUARE_NB];
211 Bitboard byTypeBB[PIECE_TYPE_NB];
212 Bitboard byColorBB[COLOR_NB];
213 int pieceCount[COLOR_NB][PIECE_TYPE_NB];
214 Square pieceList[COLOR_NB][PIECE_TYPE_NB][16];
215 int index[SQUARE_NB];
218 int castleRightsMask[SQUARE_NB];
219 Square castleRookSquare[COLOR_NB][CASTLING_SIDE_NB];
220 Bitboard castlePath[COLOR_NB][CASTLING_SIDE_NB];
221 StateInfo startState;
230 inline int64_t Position::nodes_searched() const {
234 inline void Position::set_nodes_searched(int64_t n) {
238 inline Piece Position::piece_on(Square s) const {
242 inline Piece Position::piece_moved(Move m) const {
243 return board[from_sq(m)];
246 inline bool Position::is_empty(Square s) const {
247 return board[s] == NO_PIECE;
250 inline Color Position::side_to_move() const {
254 inline Bitboard Position::pieces() const {
255 return byTypeBB[ALL_PIECES];
258 inline Bitboard Position::pieces(PieceType pt) const {
262 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2) const {
263 return byTypeBB[pt1] | byTypeBB[pt2];
266 inline Bitboard Position::pieces(Color c) const {
270 inline Bitboard Position::pieces(Color c, PieceType pt) const {
271 return byColorBB[c] & byTypeBB[pt];
274 inline Bitboard Position::pieces(Color c, PieceType pt1, PieceType pt2) const {
275 return byColorBB[c] & (byTypeBB[pt1] | byTypeBB[pt2]);
278 inline int Position::piece_count(Color c, PieceType pt) const {
279 return pieceCount[c][pt];
282 inline const Square* Position::piece_list(Color c, PieceType pt) const {
283 return pieceList[c][pt];
286 inline Square Position::ep_square() const {
290 inline Square Position::king_square(Color c) const {
291 return pieceList[c][KING][0];
294 inline int Position::can_castle(CastleRight f) const {
295 return st->castleRights & f;
298 inline int Position::can_castle(Color c) const {
299 return st->castleRights & ((WHITE_OO | WHITE_OOO) << (2 * c));
302 inline bool Position::castle_impeded(Color c, CastlingSide s) const {
303 return byTypeBB[ALL_PIECES] & castlePath[c][s];
306 inline Square Position::castle_rook_square(Color c, CastlingSide s) const {
307 return castleRookSquare[c][s];
310 template<PieceType Pt>
311 inline Bitboard Position::attacks_from(Square s) const {
313 return Pt == BISHOP || Pt == ROOK ? attacks_bb<Pt>(s, pieces())
314 : Pt == QUEEN ? attacks_from<ROOK>(s) | attacks_from<BISHOP>(s)
315 : StepAttacksBB[Pt][s];
319 inline Bitboard Position::attacks_from<PAWN>(Square s, Color c) const {
320 return StepAttacksBB[make_piece(c, PAWN)][s];
323 inline Bitboard Position::attacks_from(Piece p, Square s) const {
324 return attacks_from(p, s, byTypeBB[ALL_PIECES]);
327 inline Bitboard Position::attackers_to(Square s) const {
328 return attackers_to(s, byTypeBB[ALL_PIECES]);
331 inline Bitboard Position::checkers() const {
332 return st->checkersBB;
335 inline bool Position::in_check() const {
336 return st->checkersBB != 0;
339 inline Bitboard Position::discovered_check_candidates() const {
340 return hidden_checkers<false>();
343 inline Bitboard Position::pinned_pieces() const {
344 return hidden_checkers<true>();
347 inline bool Position::pawn_is_passed(Color c, Square s) const {
348 return !(pieces(~c, PAWN) & passed_pawn_mask(c, s));
351 inline Key Position::key() const {
355 inline Key Position::exclusion_key() const {
356 return st->key ^ Zobrist::exclusion;
359 inline Key Position::pawn_key() const {
363 inline Key Position::material_key() const {
364 return st->materialKey;
367 inline Score Position::psq_delta(Piece p, Square from, Square to) const {
368 return pieceSquareTable[p][to] - pieceSquareTable[p][from];
371 inline Score Position::psq_score() const {
375 inline Value Position::non_pawn_material(Color c) const {
376 return st->npMaterial[c];
379 inline bool Position::is_passed_pawn_push(Move m) const {
381 return type_of(piece_moved(m)) == PAWN
382 && pawn_is_passed(sideToMove, to_sq(m));
385 inline int Position::startpos_ply_counter() const {
386 return startPosPly + st->pliesFromNull; // HACK
389 inline bool Position::opposite_bishops() const {
391 return pieceCount[WHITE][BISHOP] == 1
392 && pieceCount[BLACK][BISHOP] == 1
393 && opposite_colors(pieceList[WHITE][BISHOP][0], pieceList[BLACK][BISHOP][0]);
396 inline bool Position::bishop_pair(Color c) const {
398 return pieceCount[c][BISHOP] >= 2
399 && opposite_colors(pieceList[c][BISHOP][0], pieceList[c][BISHOP][1]);
402 inline bool Position::pawn_on_7th(Color c) const {
403 return pieces(c, PAWN) & rank_bb(relative_rank(c, RANK_7));
406 inline bool Position::is_chess960() const {
410 inline bool Position::is_capture_or_promotion(Move m) const {
413 return type_of(m) ? type_of(m) != CASTLE : !is_empty(to_sq(m));
416 inline bool Position::is_capture(Move m) const {
418 // Note that castle is coded as "king captures the rook"
420 return (!is_empty(to_sq(m)) && type_of(m) != CASTLE) || type_of(m) == ENPASSANT;
423 inline PieceType Position::captured_piece_type() const {
424 return st->capturedType;
427 inline Thread* Position::this_thread() const {
431 #endif // !defined(POSITION_H_INCLUDED)