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.
36 explicit CheckInfo(const Position&);
38 Bitboard dcCandidates;
45 /// The StateInfo struct stores information we need to restore a Position
46 /// object to its previous state when we retract a move. Whenever a move
47 /// is made on the board (by calling Position::do_move), an StateInfo object
48 /// must be passed as a parameter.
51 Key pawnKey, materialKey;
53 int castleRights, rule50, pliesFromNull;
59 PieceType capturedType;
63 struct ReducedStateInfo {
64 Key pawnKey, materialKey;
66 int castleRights, rule50, pliesFromNull;
72 /// The position data structure. A position consists of the following data:
74 /// * For each piece type, a bitboard representing the squares occupied
75 /// by pieces of that type.
76 /// * For each color, a bitboard representing the squares occupied by
77 /// pieces of that color.
78 /// * A bitboard of all occupied squares.
79 /// * A bitboard of all checking pieces.
80 /// * A 64-entry array of pieces, indexed by the squares of the board.
81 /// * The current side to move.
82 /// * Information about the castling rights for both sides.
83 /// * The initial files of the kings and both pairs of rooks. This is
84 /// used to implement the Chess960 castling rules.
85 /// * The en passant square (which is SQ_NONE if no en passant capture is
87 /// * The squares of the kings for both sides.
88 /// * Hash keys for the position itself, the current pawn structure, and
89 /// the current material situation.
90 /// * Hash keys for all previous positions in the game for detecting
92 /// * A counter for detecting 50 move rule draws.
97 Position(const Position& p) { *this = p; }
98 Position(const Position& p, Thread* t) { *this = p; thisThread = t; }
99 Position(const std::string& f, bool c960, Thread* t) { from_fen(f, c960, t); }
100 Position& operator=(const Position&);
103 void from_fen(const std::string& fen, bool isChess960, Thread* th);
104 const std::string to_fen() const;
105 void print(Move m = MOVE_NONE) const;
107 // Position representation
108 Bitboard pieces() const;
109 Bitboard pieces(PieceType pt) const;
110 Bitboard pieces(PieceType pt1, PieceType pt2) const;
111 Bitboard pieces(Color c) const;
112 Bitboard pieces(Color c, PieceType pt) const;
113 Bitboard pieces(Color c, PieceType pt1, PieceType pt2) const;
114 Piece piece_on(Square s) const;
115 Square king_square(Color c) const;
116 Square ep_square() const;
117 bool is_empty(Square s) const;
118 const Square* piece_list(Color c, PieceType pt) const;
119 int piece_count(Color c, PieceType pt) const;
122 int can_castle(CastleRight f) const;
123 int can_castle(Color c) const;
124 bool castle_impeded(Color c, CastlingSide s) const;
125 Square castle_rook_square(Color c, CastlingSide s) const;
128 bool in_check() const;
129 Bitboard checkers() const;
130 Bitboard discovered_check_candidates() const;
131 Bitboard pinned_pieces() const;
133 // Attacks to/from a given square
134 Bitboard attackers_to(Square s) const;
135 Bitboard attackers_to(Square s, Bitboard occ) const;
136 Bitboard attacks_from(Piece p, Square s) const;
137 static Bitboard attacks_from(Piece p, Square s, Bitboard occ);
138 template<PieceType> Bitboard attacks_from(Square s) const;
139 template<PieceType> Bitboard attacks_from(Square s, Color c) const;
141 // Properties of moves
142 bool move_gives_check(Move m, const CheckInfo& ci) const;
143 bool move_attacks_square(Move m, Square s) const;
144 bool move_is_legal(const Move m) const;
145 bool pl_move_is_legal(Move m, Bitboard pinned) const;
146 bool is_pseudo_legal(const Move m) const;
147 bool is_capture(Move m) const;
148 bool is_capture_or_promotion(Move m) const;
149 bool is_passed_pawn_push(Move m) const;
150 Piece piece_moved(Move m) const;
151 PieceType captured_piece_type() const;
154 bool pawn_is_passed(Color c, Square s) const;
155 bool pawn_on_7th(Color c) const;
156 bool opposite_bishops() const;
157 bool bishop_pair(Color c) const;
159 // Doing and undoing moves
160 void do_move(Move m, StateInfo& st);
161 void do_move(Move m, StateInfo& st, const CheckInfo& ci, bool moveIsCheck);
162 void undo_move(Move m);
163 template<bool Do> void do_null_move(StateInfo& st);
165 // Static exchange evaluation
166 int see(Move m) const;
167 int see_sign(Move m) const;
169 // Accessing hash keys
171 Key exclusion_key() const;
172 Key pawn_key() const;
173 Key material_key() const;
175 // Incremental piece-square evaluation
176 Score psq_score() const;
177 Score psq_delta(Piece p, Square from, Square to) const;
178 Value non_pawn_material(Color c) const;
180 // Other properties of the position
181 Color side_to_move() const;
182 int startpos_ply_counter() const;
183 bool is_chess960() const;
184 Thread* this_thread() const;
185 int64_t nodes_searched() const;
186 void set_nodes_searched(int64_t n);
187 template<bool SkipRepetition> bool is_draw() const;
189 // Position consistency check, for debugging
190 bool pos_is_ok(int* failedStep = NULL) const;
193 // Global initialization
197 // Initialization helpers (used while setting up a position)
199 void put_piece(Piece p, Square s);
200 void set_castle_right(Color c, Square rfrom);
202 // Helper template functions
203 template<bool Do> void do_castle_move(Move m);
204 template<bool FindPinned> Bitboard hidden_checkers() const;
206 // Computing hash keys from scratch (for initialization and debugging)
207 Key compute_key() const;
208 Key compute_pawn_key() const;
209 Key compute_material_key() const;
211 // Computing incremental evaluation scores and material counts
212 Score compute_psq_score() const;
213 Value compute_non_pawn_material(Color c) const;
216 Piece board[64]; // [square]
217 Bitboard byTypeBB[8]; // [pieceType]
218 Bitboard byColorBB[2]; // [color]
219 int pieceCount[2][8]; // [color][pieceType]
220 Square pieceList[2][8][16]; // [color][pieceType][index]
221 int index[64]; // [square]
224 int castleRightsMask[64]; // [square]
225 Square castleRookSquare[2][2]; // [color][side]
226 Bitboard castlePath[2][2]; // [color][side]
227 StateInfo startState;
236 static Score pieceSquareTable[16][64]; // [piece][square]
237 static Key zobrist[2][8][64]; // [color][pieceType][square]/[piece count]
238 static Key zobEp[8]; // [file]
239 static Key zobCastle[16]; // [castleRight]
240 static Key zobSideToMove;
241 static Key zobExclusion;
244 inline int64_t Position::nodes_searched() const {
248 inline void Position::set_nodes_searched(int64_t n) {
252 inline Piece Position::piece_on(Square s) const {
256 inline Piece Position::piece_moved(Move m) const {
257 return board[from_sq(m)];
260 inline bool Position::is_empty(Square s) const {
261 return board[s] == NO_PIECE;
264 inline Color Position::side_to_move() const {
268 inline Bitboard Position::pieces() const {
269 return byTypeBB[ALL_PIECES];
272 inline Bitboard Position::pieces(PieceType pt) const {
276 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2) const {
277 return byTypeBB[pt1] | byTypeBB[pt2];
280 inline Bitboard Position::pieces(Color c) const {
284 inline Bitboard Position::pieces(Color c, PieceType pt) const {
285 return byColorBB[c] & byTypeBB[pt];
288 inline Bitboard Position::pieces(Color c, PieceType pt1, PieceType pt2) const {
289 return byColorBB[c] & (byTypeBB[pt1] | byTypeBB[pt2]);
292 inline int Position::piece_count(Color c, PieceType pt) const {
293 return pieceCount[c][pt];
296 inline const Square* Position::piece_list(Color c, PieceType pt) const {
297 return pieceList[c][pt];
300 inline Square Position::ep_square() const {
304 inline Square Position::king_square(Color c) const {
305 return pieceList[c][KING][0];
308 inline int Position::can_castle(CastleRight f) const {
309 return st->castleRights & f;
312 inline int Position::can_castle(Color c) const {
313 return st->castleRights & ((WHITE_OO | WHITE_OOO) << (2 * c));
316 inline bool Position::castle_impeded(Color c, CastlingSide s) const {
317 return byTypeBB[ALL_PIECES] & castlePath[c][s];
320 inline Square Position::castle_rook_square(Color c, CastlingSide s) const {
321 return castleRookSquare[c][s];
324 template<PieceType Pt>
325 inline Bitboard Position::attacks_from(Square s) const {
327 return Pt == BISHOP || Pt == ROOK ? attacks_bb<Pt>(s, pieces())
328 : Pt == QUEEN ? attacks_from<ROOK>(s) | attacks_from<BISHOP>(s)
329 : StepAttacksBB[Pt][s];
333 inline Bitboard Position::attacks_from<PAWN>(Square s, Color c) const {
334 return StepAttacksBB[make_piece(c, PAWN)][s];
337 inline Bitboard Position::attacks_from(Piece p, Square s) const {
338 return attacks_from(p, s, byTypeBB[ALL_PIECES]);
341 inline Bitboard Position::attackers_to(Square s) const {
342 return attackers_to(s, byTypeBB[ALL_PIECES]);
345 inline Bitboard Position::checkers() const {
346 return st->checkersBB;
349 inline bool Position::in_check() const {
350 return st->checkersBB != 0;
353 inline Bitboard Position::discovered_check_candidates() const {
354 return hidden_checkers<false>();
357 inline Bitboard Position::pinned_pieces() const {
358 return hidden_checkers<true>();
361 inline bool Position::pawn_is_passed(Color c, Square s) const {
362 return !(pieces(~c, PAWN) & passed_pawn_mask(c, s));
365 inline Key Position::key() const {
369 inline Key Position::exclusion_key() const {
370 return st->key ^ zobExclusion;
373 inline Key Position::pawn_key() const {
377 inline Key Position::material_key() const {
378 return st->materialKey;
381 inline Score Position::psq_delta(Piece p, Square from, Square to) const {
382 return pieceSquareTable[p][to] - pieceSquareTable[p][from];
385 inline Score Position::psq_score() const {
389 inline Value Position::non_pawn_material(Color c) const {
390 return st->npMaterial[c];
393 inline bool Position::is_passed_pawn_push(Move m) const {
395 return type_of(piece_moved(m)) == PAWN
396 && pawn_is_passed(sideToMove, to_sq(m));
399 inline int Position::startpos_ply_counter() const {
400 return startPosPly + st->pliesFromNull; // HACK
403 inline bool Position::opposite_bishops() const {
405 return pieceCount[WHITE][BISHOP] == 1
406 && pieceCount[BLACK][BISHOP] == 1
407 && opposite_colors(pieceList[WHITE][BISHOP][0], pieceList[BLACK][BISHOP][0]);
410 inline bool Position::bishop_pair(Color c) const {
412 return pieceCount[c][BISHOP] >= 2
413 && opposite_colors(pieceList[c][BISHOP][0], pieceList[c][BISHOP][1]);
416 inline bool Position::pawn_on_7th(Color c) const {
417 return pieces(c, PAWN) & rank_bb(relative_rank(c, RANK_7));
420 inline bool Position::is_chess960() const {
424 inline bool Position::is_capture_or_promotion(Move m) const {
427 return type_of(m) ? type_of(m) != CASTLE : !is_empty(to_sq(m));
430 inline bool Position::is_capture(Move m) const {
432 // Note that castle is coded as "king captures the rook"
434 return (!is_empty(to_sq(m)) && type_of(m) != CASTLE) || type_of(m) == ENPASSANT;
437 inline PieceType Position::captured_piece_type() const {
438 return st->capturedType;
441 inline Thread* Position::this_thread() const {
445 #endif // !defined(POSITION_H_INCLUDED)