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.
35 explicit CheckInfo(const Position&);
37 Bitboard dcCandidates;
44 /// The StateInfo struct stores information we need to restore a Position
45 /// object to its previous state when we retract a move. Whenever a move
46 /// is made on the board (by calling Position::do_move), an StateInfo object
47 /// must be passed as a parameter.
50 Key pawnKey, materialKey;
52 int castleRights, rule50, pliesFromNull;
58 PieceType capturedType;
63 /// The position data structure. A position consists of the following data:
65 /// * For each piece type, a bitboard representing the squares occupied
66 /// by pieces of that type.
67 /// * For each color, a bitboard representing the squares occupied by
68 /// pieces of that color.
69 /// * A bitboard of all occupied squares.
70 /// * A bitboard of all checking pieces.
71 /// * A 64-entry array of pieces, indexed by the squares of the board.
72 /// * The current side to move.
73 /// * Information about the castling rights for both sides.
74 /// * The initial files of the kings and both pairs of rooks. This is
75 /// used to implement the Chess960 castling rules.
76 /// * The en passant square (which is SQ_NONE if no en passant capture is
78 /// * The squares of the kings for both sides.
79 /// * Hash keys for the position itself, the current pawn structure, and
80 /// the current material situation.
81 /// * Hash keys for all previous positions in the game for detecting
83 /// * A counter for detecting 50 move rule draws.
87 // No copy c'tor or assignment operator allowed
88 Position(const Position&);
89 Position& operator=(const Position&);
93 Position(const Position& pos, int th) { copy(pos, th); }
94 Position(const std::string& fen, bool isChess960, int th);
97 void copy(const Position& pos, int th);
98 void from_fen(const std::string& fen, bool isChess960);
99 const std::string to_fen() const;
100 void print(Move m = MOVE_NONE) const;
102 // Position representation
103 Bitboard pieces() const;
104 Bitboard pieces(Color c) const;
105 Bitboard pieces(PieceType pt) const;
106 Bitboard pieces(PieceType pt, Color c) const;
107 Bitboard pieces(PieceType pt1, PieceType pt2) const;
108 Bitboard pieces(PieceType pt1, PieceType pt2, Color c) const;
109 Piece piece_on(Square s) const;
110 Square king_square(Color c) const;
111 Square ep_square() const;
112 bool square_empty(Square s) const;
113 const Square* piece_list(Color c, PieceType pt) const;
114 int piece_count(Color c, PieceType pt) const;
117 bool can_castle(CastleRight f) const;
118 bool can_castle(Color c) const;
119 bool castle_impeded(CastleRight f) const;
120 Square castle_rook_square(CastleRight f) const;
123 bool in_check() const;
124 Bitboard checkers() const;
125 Bitboard discovered_check_candidates() const;
126 Bitboard pinned_pieces() const;
128 // Attacks to/from a given square
129 Bitboard attackers_to(Square s) const;
130 Bitboard attackers_to(Square s, Bitboard occ) const;
131 Bitboard attacks_from(Piece p, Square s) const;
132 static Bitboard attacks_from(Piece p, Square s, Bitboard occ);
133 template<PieceType> Bitboard attacks_from(Square s) const;
134 template<PieceType> Bitboard attacks_from(Square s, Color c) const;
136 // Properties of moves
137 bool move_gives_check(Move m, const CheckInfo& ci) const;
138 bool move_attacks_square(Move m, Square s) 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 int this_thread() const;
179 int64_t nodes_searched() const;
180 void set_nodes_searched(int64_t n);
181 template<bool SkipRepetition> bool is_draw() const;
183 // Position consistency check, for debugging
184 bool pos_is_ok(int* failedStep = NULL) const;
187 // Global initialization
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);
195 bool move_is_legal(const Move m) const;
197 // Helper template functions
198 template<bool Do> void do_castle_move(Move m);
199 template<bool FindPinned> Bitboard hidden_checkers() const;
201 // Computing hash keys from scratch (for initialization and debugging)
202 Key compute_key() const;
203 Key compute_pawn_key() const;
204 Key compute_material_key() const;
206 // Computing incremental evaluation scores and material counts
207 Score compute_psq_score() const;
208 Value compute_non_pawn_material(Color c) const;
211 Piece board[64]; // [square]
212 Bitboard byTypeBB[8]; // [pieceType]
213 Bitboard byColorBB[2]; // [color]
214 int pieceCount[2][8]; // [color][pieceType]
215 Square pieceList[2][8][16]; // [color][pieceType][index]
216 int index[64]; // [square]
219 int castleRightsMask[64]; // [square]
220 Square castleRookSquare[16]; // [castleRight]
221 Bitboard castlePath[16]; // [castleRight]
222 StateInfo startState;
231 static Score pieceSquareTable[16][64]; // [piece][square]
232 static Key zobrist[2][8][64]; // [color][pieceType][square]/[piece count]
233 static Key zobEp[8]; // [file]
234 static Key zobCastle[16]; // [castleRight]
235 static Key zobSideToMove;
236 static Key zobExclusion;
239 inline int64_t Position::nodes_searched() const {
243 inline void Position::set_nodes_searched(int64_t n) {
247 inline Piece Position::piece_on(Square s) const {
251 inline Piece Position::piece_moved(Move m) const {
252 return board[from_sq(m)];
255 inline bool Position::square_empty(Square s) const {
256 return board[s] == NO_PIECE;
259 inline Color Position::side_to_move() const {
263 inline Bitboard Position::pieces() const {
264 return byTypeBB[ALL_PIECES];
267 inline Bitboard Position::pieces(Color c) const {
271 inline Bitboard Position::pieces(PieceType pt) const {
275 inline Bitboard Position::pieces(PieceType pt, Color c) const {
276 return byTypeBB[pt] & byColorBB[c];
279 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2) const {
280 return byTypeBB[pt1] | byTypeBB[pt2];
283 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2, Color c) const {
284 return (byTypeBB[pt1] | byTypeBB[pt2]) & byColorBB[c];
287 inline int Position::piece_count(Color c, PieceType pt) const {
288 return pieceCount[c][pt];
291 inline const Square* Position::piece_list(Color c, PieceType pt) const {
292 return pieceList[c][pt];
295 inline Square Position::ep_square() const {
299 inline Square Position::king_square(Color c) const {
300 return pieceList[c][KING][0];
303 inline bool Position::can_castle(CastleRight f) const {
304 return st->castleRights & f;
307 inline bool Position::can_castle(Color c) const {
308 return st->castleRights & ((WHITE_OO | WHITE_OOO) << c);
311 inline bool Position::castle_impeded(CastleRight f) const {
312 return byTypeBB[ALL_PIECES] & castlePath[f];
315 inline Square Position::castle_rook_square(CastleRight f) const {
316 return castleRookSquare[f];
319 template<PieceType Pt>
320 inline Bitboard Position::attacks_from(Square s) const {
322 return Pt == BISHOP || Pt == ROOK ? attacks_bb<Pt>(s, pieces())
323 : Pt == QUEEN ? attacks_from<ROOK>(s) | attacks_from<BISHOP>(s)
324 : StepAttacksBB[Pt][s];
328 inline Bitboard Position::attacks_from<PAWN>(Square s, Color c) const {
329 return StepAttacksBB[make_piece(c, PAWN)][s];
332 inline Bitboard Position::attacks_from(Piece p, Square s) const {
333 return attacks_from(p, s, byTypeBB[ALL_PIECES]);
336 inline Bitboard Position::attackers_to(Square s) const {
337 return attackers_to(s, byTypeBB[ALL_PIECES]);
340 inline Bitboard Position::checkers() const {
341 return st->checkersBB;
344 inline bool Position::in_check() const {
345 return st->checkersBB != 0;
348 inline Bitboard Position::discovered_check_candidates() const {
349 return hidden_checkers<false>();
352 inline Bitboard Position::pinned_pieces() const {
353 return hidden_checkers<true>();
356 inline bool Position::pawn_is_passed(Color c, Square s) const {
357 return !(pieces(PAWN, ~c) & passed_pawn_mask(c, s));
360 inline Key Position::key() const {
364 inline Key Position::exclusion_key() const {
365 return st->key ^ zobExclusion;
368 inline Key Position::pawn_key() const {
372 inline Key Position::material_key() const {
373 return st->materialKey;
376 inline Score Position::psq_delta(Piece p, Square from, Square to) const {
377 return pieceSquareTable[p][to] - pieceSquareTable[p][from];
380 inline Score Position::psq_score() const {
384 inline Value Position::non_pawn_material(Color c) const {
385 return st->npMaterial[c];
388 inline bool Position::is_passed_pawn_push(Move m) const {
390 return type_of(piece_moved(m)) == PAWN
391 && pawn_is_passed(sideToMove, to_sq(m));
394 inline int Position::startpos_ply_counter() const {
395 return startPosPly + st->pliesFromNull; // HACK
398 inline bool Position::opposite_bishops() const {
400 return pieceCount[WHITE][BISHOP] == 1
401 && pieceCount[BLACK][BISHOP] == 1
402 && opposite_colors(pieceList[WHITE][BISHOP][0], pieceList[BLACK][BISHOP][0]);
405 inline bool Position::bishop_pair(Color c) const {
407 return pieceCount[c][BISHOP] >= 2
408 && opposite_colors(pieceList[c][BISHOP][0], pieceList[c][BISHOP][1]);
411 inline bool Position::pawn_on_7th(Color c) const {
412 return pieces(PAWN, c) & rank_bb(relative_rank(c, RANK_7));
415 inline bool Position::is_chess960() const {
419 inline bool Position::is_capture_or_promotion(Move m) const {
422 return is_special(m) ? !is_castle(m) : !square_empty(to_sq(m));
425 inline bool Position::is_capture(Move m) const {
427 // Note that castle is coded as "king captures the rook"
429 return (!square_empty(to_sq(m)) && !is_castle(m)) || is_enpassant(m);
432 inline PieceType Position::captured_piece_type() const {
433 return st->capturedType;
436 inline int Position::this_thread() const {
440 #endif // !defined(POSITION_H_INCLUDED)