2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2010 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 /// Maximum number of plies per game (220 should be enough, because the
30 /// maximum search depth is 100, and during position setup we reset the
31 /// move counter for every non-reversible move).
32 const int MaxGameLength = 220;
35 /// The checkInfo struct is initialized at c'tor time and keeps info used
36 /// to detect if a move gives check.
40 explicit CheckInfo(const Position&);
42 Bitboard dcCandidates;
48 /// The StateInfo struct stores information we need to restore a Position
49 /// object to its previous state when we retract a move. Whenever a move
50 /// is made on the board (by calling Position::do_move), an StateInfo object
51 /// must be passed as a parameter.
55 Key pawnKey, materialKey;
56 int castleRights, rule50, gamePly, pliesFromNull;
63 PieceType capturedType;
68 /// The position data structure. A position consists of the following data:
70 /// * For each piece type, a bitboard representing the squares occupied
71 /// by pieces of that type.
72 /// * For each color, a bitboard representing the squares occupied by
73 /// pieces of that color.
74 /// * A bitboard of all occupied squares.
75 /// * A bitboard of all checking pieces.
76 /// * A 64-entry array of pieces, indexed by the squares of the board.
77 /// * The current side to move.
78 /// * Information about the castling rights for both sides.
79 /// * The initial files of the kings and both pairs of rooks. This is
80 /// used to implement the Chess960 castling rules.
81 /// * The en passant square (which is SQ_NONE if no en passant capture is
83 /// * The squares of the kings for both sides.
84 /// * Hash keys for the position itself, the current pawn structure, and
85 /// the current material situation.
86 /// * Hash keys for all previous positions in the game for detecting
88 /// * A counter for detecting 50 move rule draws.
92 // No default or copy c'tor allowed, default c'tor will not be generated
93 // anyhow because of user-defined c'tors.
94 Position(const Position&);
97 Position(const Position& pos, int threadID);
98 Position(const std::string& fen, bool isChess960, int threadID);
101 void from_fen(const std::string& fen, bool isChess960);
102 const std::string to_fen() const;
103 void print(Move m = MOVE_NONE) const;
105 // The piece on a given square
106 Piece piece_on(Square s) const;
107 bool square_is_empty(Square s) const;
110 Color side_to_move() const;
112 // Bitboard representation of the position
113 Bitboard empty_squares() const;
114 Bitboard occupied_squares() const;
115 Bitboard pieces(Color c) const;
116 Bitboard pieces(PieceType pt) const;
117 Bitboard pieces(PieceType pt, Color c) const;
118 Bitboard pieces(PieceType pt1, PieceType pt2) const;
119 Bitboard pieces(PieceType pt1, PieceType pt2, Color c) const;
121 // Number of pieces of each color and type
122 int piece_count(Color c, PieceType pt) const;
124 // The en passant square
125 Square ep_square() const;
127 // Current king position for each color
128 Square king_square(Color c) const;
131 bool can_castle(CastleRight f) const;
132 bool can_castle(Color c) const;
133 Square castle_rook_square(CastleRight f) const;
135 // Bitboards for pinned pieces and discovered check candidates
136 Bitboard discovered_check_candidates(Color c) const;
137 Bitboard pinned_pieces(Color c) const;
139 // Checking pieces and under check information
140 Bitboard checkers() const;
141 bool in_check() const;
144 const Square* piece_list(Color c, PieceType pt) const;
146 // Information about attacks to or from a given square
147 Bitboard attackers_to(Square s) const;
148 Bitboard attackers_to(Square s, Bitboard occ) const;
149 Bitboard attacks_from(Piece p, Square s) const;
150 static Bitboard attacks_from(Piece p, Square s, Bitboard occ);
151 template<PieceType> Bitboard attacks_from(Square s) const;
152 template<PieceType> Bitboard attacks_from(Square s, Color c) const;
154 // Properties of moves
155 bool pl_move_is_legal(Move m, Bitboard pinned) const;
156 bool move_is_pl(const Move m) const;
157 bool move_gives_check(Move m, const CheckInfo& ci) const;
158 bool move_is_capture(Move m) const;
159 bool move_is_capture_or_promotion(Move m) const;
160 bool move_is_passed_pawn_push(Move m) const;
161 bool move_attacks_square(Move m, Square s) const;
163 // Piece captured with previous moves
164 PieceType captured_piece_type() const;
166 // Information about pawns
167 bool pawn_is_passed(Color c, Square s) const;
169 // Doing and undoing moves
170 void do_setup_move(Move m);
171 void do_move(Move m, StateInfo& st);
172 void do_move(Move m, StateInfo& st, const CheckInfo& ci, bool moveIsCheck);
173 void undo_move(Move m);
174 void do_null_move(StateInfo& st);
175 void undo_null_move();
177 // Static exchange evaluation
178 int see(Move m) const;
179 int see_sign(Move m) const;
181 // Accessing hash keys
183 Key get_exclusion_key() const;
184 Key get_pawn_key() const;
185 Key get_material_key() const;
187 // Incremental evaluation
189 Value non_pawn_material(Color c) const;
190 Score pst_delta(Piece piece, Square from, Square to) const;
192 // Game termination checks
193 bool is_mate() const;
194 template<bool SkipRepetition> bool is_draw() const;
196 // Number of plies from starting position
197 int startpos_ply_counter() const;
199 // Other properties of the position
200 bool opposite_colored_bishops() const;
201 bool has_pawn_on_7th(Color c) const;
202 bool is_chess960() const;
204 // Current thread ID searching on the position
207 int64_t nodes_searched() const;
208 void set_nodes_searched(int64_t n);
210 // Position consistency check, for debugging
211 bool is_ok(int* failedStep = NULL) const;
214 // Global initialization
219 // Initialization helper functions (used while setting up a position)
222 void put_piece(Piece p, Square s);
223 void set_castle(int f, Square ksq, Square rsq);
224 void set_castling_rights(char token);
225 bool move_is_legal(const Move m) const;
227 // Helper functions for doing and undoing moves
228 void do_capture_move(Key& key, PieceType capture, Color them, Square to, bool ep);
229 void do_castle_move(Move m);
230 void undo_castle_move(Move m);
232 template<bool FindPinned>
233 Bitboard hidden_checkers(Color c) const;
235 // Computing hash keys from scratch (for initialization and debugging)
236 Key compute_key() const;
237 Key compute_pawn_key() const;
238 Key compute_material_key() const;
240 // Computing incremental evaluation scores and material counts
241 Score pst(Piece p, Square s) const;
242 Score compute_value() const;
243 Value compute_non_pawn_material(Color c) const;
246 Piece board[64]; // [square]
249 Bitboard byTypeBB[8]; // [pieceType]
250 Bitboard byColorBB[2]; // [color]
253 int pieceCount[2][8]; // [color][pieceType]
256 Square pieceList[2][8][16]; // [color][pieceType][index]
257 int index[64]; // [square]
260 Key history[MaxGameLength];
261 int castleRightsMask[64]; // [square]
262 Square castleRookSquare[16]; // [castleRight]
263 StateInfo startState;
272 static Score pieceSquareTable[16][64]; // [piece][square]
273 static Key zobrist[2][8][64]; // [color][pieceType][square]
274 static Key zobEp[64]; // [square]
275 static Key zobCastle[16]; // [castleRight]
276 static Key zobSideToMove;
277 static Key zobExclusion;
280 inline int64_t Position::nodes_searched() const {
284 inline void Position::set_nodes_searched(int64_t n) {
288 inline Piece Position::piece_on(Square s) const {
292 inline bool Position::square_is_empty(Square s) const {
293 return piece_on(s) == PIECE_NONE;
296 inline Color Position::side_to_move() const {
300 inline Bitboard Position::occupied_squares() const {
304 inline Bitboard Position::empty_squares() const {
305 return ~occupied_squares();
308 inline Bitboard Position::pieces(Color c) const {
312 inline Bitboard Position::pieces(PieceType pt) const {
316 inline Bitboard Position::pieces(PieceType pt, Color c) const {
317 return byTypeBB[pt] & byColorBB[c];
320 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2) const {
321 return byTypeBB[pt1] | byTypeBB[pt2];
324 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2, Color c) const {
325 return (byTypeBB[pt1] | byTypeBB[pt2]) & byColorBB[c];
328 inline int Position::piece_count(Color c, PieceType pt) const {
329 return pieceCount[c][pt];
332 inline const Square* Position::piece_list(Color c, PieceType pt) const {
333 return pieceList[c][pt];
336 inline Square Position::ep_square() const {
340 inline Square Position::king_square(Color c) const {
341 return pieceList[c][KING][0];
344 inline bool Position::can_castle(CastleRight f) const {
345 return st->castleRights & f;
348 inline bool Position::can_castle(Color c) const {
349 return st->castleRights & ((WHITE_OO | WHITE_OOO) << c);
352 inline Square Position::castle_rook_square(CastleRight f) const {
353 return castleRookSquare[f];
357 inline Bitboard Position::attacks_from<PAWN>(Square s, Color c) const {
358 return StepAttacksBB[make_piece(c, PAWN)][s];
361 template<PieceType Piece> // Knight and King and white pawns
362 inline Bitboard Position::attacks_from(Square s) const {
363 return StepAttacksBB[Piece][s];
367 inline Bitboard Position::attacks_from<BISHOP>(Square s) const {
368 return bishop_attacks_bb(s, occupied_squares());
372 inline Bitboard Position::attacks_from<ROOK>(Square s) const {
373 return rook_attacks_bb(s, occupied_squares());
377 inline Bitboard Position::attacks_from<QUEEN>(Square s) const {
378 return attacks_from<ROOK>(s) | attacks_from<BISHOP>(s);
381 inline Bitboard Position::checkers() const {
382 return st->checkersBB;
385 inline bool Position::in_check() const {
386 return st->checkersBB != EmptyBoardBB;
389 inline bool Position::pawn_is_passed(Color c, Square s) const {
390 return !(pieces(PAWN, opposite_color(c)) & passed_pawn_mask(c, s));
393 inline Key Position::get_key() const {
397 inline Key Position::get_exclusion_key() const {
398 return st->key ^ zobExclusion;
401 inline Key Position::get_pawn_key() const {
405 inline Key Position::get_material_key() const {
406 return st->materialKey;
409 inline Score Position::pst(Piece p, Square s) const {
410 return pieceSquareTable[p][s];
413 inline Score Position::pst_delta(Piece piece, Square from, Square to) const {
414 return pieceSquareTable[piece][to] - pieceSquareTable[piece][from];
417 inline Score Position::value() const {
421 inline Value Position::non_pawn_material(Color c) const {
422 return st->npMaterial[c];
425 inline bool Position::move_is_passed_pawn_push(Move m) const {
427 Color c = side_to_move();
428 return piece_on(move_from(m)) == make_piece(c, PAWN)
429 && pawn_is_passed(c, move_to(m));
432 inline int Position::startpos_ply_counter() const {
433 return Max(2 * (fullMoves - 1), 0) + int(sideToMove == BLACK);
436 inline bool Position::opposite_colored_bishops() const {
438 return piece_count(WHITE, BISHOP) == 1
439 && piece_count(BLACK, BISHOP) == 1
440 && opposite_color_squares(piece_list(WHITE, BISHOP)[0], piece_list(BLACK, BISHOP)[0]);
443 inline bool Position::has_pawn_on_7th(Color c) const {
444 return pieces(PAWN, c) & rank_bb(relative_rank(c, RANK_7));
447 inline bool Position::is_chess960() const {
451 inline bool Position::move_is_capture_or_promotion(Move m) const {
453 assert(move_is_ok(m));
454 return move_is_special(m) ? !move_is_castle(m) : !square_is_empty(move_to(m));
457 inline bool Position::move_is_capture(Move m) const {
459 // Note that castle is coded as "king captures the rook"
460 assert(move_is_ok(m));
461 return (!square_is_empty(move_to(m)) && !move_is_castle(m)) || move_is_ep(m);
464 inline PieceType Position::captured_piece_type() const {
465 return st->capturedType;
468 inline int Position::thread() const {
472 #endif // !defined(POSITION_H_INCLUDED)