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;
64 /// The position data structure. A position consists of the following data:
66 /// * For each piece type, a bitboard representing the squares occupied
67 /// by pieces of that type.
68 /// * For each color, a bitboard representing the squares occupied by
69 /// pieces of that color.
70 /// * A bitboard of all occupied squares.
71 /// * A bitboard of all checking pieces.
72 /// * A 64-entry array of pieces, indexed by the squares of the board.
73 /// * The current side to move.
74 /// * Information about the castling rights for both sides.
75 /// * The initial files of the kings and both pairs of rooks. This is
76 /// used to implement the Chess960 castling rules.
77 /// * The en passant square (which is SQ_NONE if no en passant capture is
79 /// * The squares of the kings for both sides.
80 /// * Hash keys for the position itself, the current pawn structure, and
81 /// the current material situation.
82 /// * Hash keys for all previous positions in the game for detecting
84 /// * A counter for detecting 50 move rule draws.
89 Position(const Position& p) { *this = p; }
90 Position(const std::string& f, bool c960) { from_fen(f, c960); }
91 Position& operator=(const Position&);
94 void from_fen(const std::string& fen, bool isChess960);
95 const std::string to_fen() const;
96 void print(Move m = MOVE_NONE) const;
98 // Position representation
99 Bitboard pieces() const;
100 Bitboard pieces(Color c) const;
101 Bitboard pieces(PieceType pt) const;
102 Bitboard pieces(PieceType pt, Color c) const;
103 Bitboard pieces(PieceType pt1, PieceType pt2) const;
104 Bitboard pieces(PieceType pt1, PieceType pt2, Color c) const;
105 Piece piece_on(Square s) const;
106 Square king_square(Color c) const;
107 Square ep_square() const;
108 bool square_empty(Square s) const;
109 const Square* piece_list(Color c, PieceType pt) const;
110 int piece_count(Color c, PieceType pt) const;
113 bool can_castle(CastleRight f) const;
114 bool can_castle(Color c) const;
115 bool castle_impeded(CastleRight f) const;
116 Square castle_rook_square(CastleRight f) const;
119 bool in_check() const;
120 Bitboard checkers() const;
121 Bitboard discovered_check_candidates() const;
122 Bitboard pinned_pieces() const;
124 // Attacks to/from a given square
125 Bitboard attackers_to(Square s) const;
126 Bitboard attackers_to(Square s, Bitboard occ) const;
127 Bitboard attacks_from(Piece p, Square s) const;
128 static Bitboard attacks_from(Piece p, Square s, Bitboard occ);
129 template<PieceType> Bitboard attacks_from(Square s) const;
130 template<PieceType> Bitboard attacks_from(Square s, Color c) const;
132 // Properties of moves
133 bool move_gives_check(Move m, const CheckInfo& ci) const;
134 bool move_attacks_square(Move m, Square s) const;
135 bool pl_move_is_legal(Move m, Bitboard pinned) const;
136 bool is_pseudo_legal(const Move m) const;
137 bool is_capture(Move m) const;
138 bool is_capture_or_promotion(Move m) const;
139 bool is_passed_pawn_push(Move m) const;
140 Piece piece_moved(Move m) const;
141 PieceType captured_piece_type() const;
144 bool pawn_is_passed(Color c, Square s) const;
145 bool pawn_on_7th(Color c) const;
146 bool opposite_bishops() const;
147 bool bishop_pair(Color c) const;
149 // Doing and undoing moves
150 void do_move(Move m, StateInfo& st);
151 void do_move(Move m, StateInfo& st, const CheckInfo& ci, bool moveIsCheck);
152 void undo_move(Move m);
153 template<bool Do> void do_null_move(StateInfo& st);
155 // Static exchange evaluation
156 int see(Move m) const;
157 int see_sign(Move m) const;
159 // Accessing hash keys
161 Key exclusion_key() const;
162 Key pawn_key() const;
163 Key material_key() const;
165 // Incremental piece-square evaluation
166 Score psq_score() const;
167 Score psq_delta(Piece p, Square from, Square to) const;
168 Value non_pawn_material(Color c) const;
170 // Other properties of the position
171 Color side_to_move() const;
172 int startpos_ply_counter() const;
173 bool is_chess960() const;
174 int64_t nodes_searched() const;
175 void set_nodes_searched(int64_t n);
176 template<bool SkipRepetition> bool is_draw() const;
178 // Position consistency check, for debugging
179 bool pos_is_ok(int* failedStep = NULL) const;
182 // Global initialization
186 // Initialization helpers (used while setting up a position)
188 void put_piece(Piece p, Square s);
189 void set_castle_right(Color c, Square rfrom);
190 bool move_is_legal(const Move m) const;
192 // Helper template functions
193 template<bool Do> void do_castle_move(Move m);
194 template<bool FindPinned> Bitboard hidden_checkers() const;
196 // Computing hash keys from scratch (for initialization and debugging)
197 Key compute_key() const;
198 Key compute_pawn_key() const;
199 Key compute_material_key() const;
201 // Computing incremental evaluation scores and material counts
202 Score compute_psq_score() const;
203 Value compute_non_pawn_material(Color c) const;
206 Piece board[64]; // [square]
207 Bitboard byTypeBB[8]; // [pieceType]
208 Bitboard byColorBB[2]; // [color]
209 int pieceCount[2][8]; // [color][pieceType]
210 Square pieceList[2][8][16]; // [color][pieceType][index]
211 int index[64]; // [square]
214 int castleRightsMask[64]; // [square]
215 Square castleRookSquare[16]; // [castleRight]
216 Bitboard castlePath[16]; // [castleRight]
217 StateInfo startState;
225 static Score pieceSquareTable[16][64]; // [piece][square]
226 static Key zobrist[2][8][64]; // [color][pieceType][square]/[piece count]
227 static Key zobEp[8]; // [file]
228 static Key zobCastle[16]; // [castleRight]
229 static Key zobSideToMove;
230 static Key zobExclusion;
233 inline int64_t Position::nodes_searched() const {
237 inline void Position::set_nodes_searched(int64_t n) {
241 inline Piece Position::piece_on(Square s) const {
245 inline Piece Position::piece_moved(Move m) const {
246 return board[from_sq(m)];
249 inline bool Position::square_empty(Square s) const {
250 return board[s] == NO_PIECE;
253 inline Color Position::side_to_move() const {
257 inline Bitboard Position::pieces() const {
258 return byTypeBB[ALL_PIECES];
261 inline Bitboard Position::pieces(Color c) const {
265 inline Bitboard Position::pieces(PieceType pt) const {
269 inline Bitboard Position::pieces(PieceType pt, Color c) const {
270 return byTypeBB[pt] & byColorBB[c];
273 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2) const {
274 return byTypeBB[pt1] | byTypeBB[pt2];
277 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2, Color c) const {
278 return (byTypeBB[pt1] | byTypeBB[pt2]) & byColorBB[c];
281 inline int Position::piece_count(Color c, PieceType pt) const {
282 return pieceCount[c][pt];
285 inline const Square* Position::piece_list(Color c, PieceType pt) const {
286 return pieceList[c][pt];
289 inline Square Position::ep_square() const {
293 inline Square Position::king_square(Color c) const {
294 return pieceList[c][KING][0];
297 inline bool Position::can_castle(CastleRight f) const {
298 return st->castleRights & f;
301 inline bool Position::can_castle(Color c) const {
302 return st->castleRights & ((WHITE_OO | WHITE_OOO) << c);
305 inline bool Position::castle_impeded(CastleRight f) const {
306 return byTypeBB[ALL_PIECES] & castlePath[f];
309 inline Square Position::castle_rook_square(CastleRight f) const {
310 return castleRookSquare[f];
313 template<PieceType Pt>
314 inline Bitboard Position::attacks_from(Square s) const {
316 return Pt == BISHOP || Pt == ROOK ? attacks_bb<Pt>(s, pieces())
317 : Pt == QUEEN ? attacks_from<ROOK>(s) | attacks_from<BISHOP>(s)
318 : StepAttacksBB[Pt][s];
322 inline Bitboard Position::attacks_from<PAWN>(Square s, Color c) const {
323 return StepAttacksBB[make_piece(c, PAWN)][s];
326 inline Bitboard Position::attacks_from(Piece p, Square s) const {
327 return attacks_from(p, s, byTypeBB[ALL_PIECES]);
330 inline Bitboard Position::attackers_to(Square s) const {
331 return attackers_to(s, byTypeBB[ALL_PIECES]);
334 inline Bitboard Position::checkers() const {
335 return st->checkersBB;
338 inline bool Position::in_check() const {
339 return st->checkersBB != 0;
342 inline Bitboard Position::discovered_check_candidates() const {
343 return hidden_checkers<false>();
346 inline Bitboard Position::pinned_pieces() const {
347 return hidden_checkers<true>();
350 inline bool Position::pawn_is_passed(Color c, Square s) const {
351 return !(pieces(PAWN, ~c) & passed_pawn_mask(c, s));
354 inline Key Position::key() const {
358 inline Key Position::exclusion_key() const {
359 return st->key ^ zobExclusion;
362 inline Key Position::pawn_key() const {
366 inline Key Position::material_key() const {
367 return st->materialKey;
370 inline Score Position::psq_delta(Piece p, Square from, Square to) const {
371 return pieceSquareTable[p][to] - pieceSquareTable[p][from];
374 inline Score Position::psq_score() const {
378 inline Value Position::non_pawn_material(Color c) const {
379 return st->npMaterial[c];
382 inline bool Position::is_passed_pawn_push(Move m) const {
384 return type_of(piece_moved(m)) == PAWN
385 && pawn_is_passed(sideToMove, to_sq(m));
388 inline int Position::startpos_ply_counter() const {
389 return startPosPly + st->pliesFromNull; // HACK
392 inline bool Position::opposite_bishops() const {
394 return pieceCount[WHITE][BISHOP] == 1
395 && pieceCount[BLACK][BISHOP] == 1
396 && opposite_colors(pieceList[WHITE][BISHOP][0], pieceList[BLACK][BISHOP][0]);
399 inline bool Position::bishop_pair(Color c) const {
401 return pieceCount[c][BISHOP] >= 2
402 && opposite_colors(pieceList[c][BISHOP][0], pieceList[c][BISHOP][1]);
405 inline bool Position::pawn_on_7th(Color c) const {
406 return pieces(PAWN, c) & rank_bb(relative_rank(c, RANK_7));
409 inline bool Position::is_chess960() const {
413 inline bool Position::is_capture_or_promotion(Move m) const {
416 return is_special(m) ? !is_castle(m) : !square_empty(to_sq(m));
419 inline bool Position::is_capture(Move m) const {
421 // Note that castle is coded as "king captures the rook"
423 return (!square_empty(to_sq(m)) && !is_castle(m)) || is_enpassant(m);
426 inline PieceType Position::captured_piece_type() const {
427 return st->capturedType;
430 #endif // !defined(POSITION_H_INCLUDED)