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 Position& p, Thread* t) { *this = p; thisThread = t; }
91 Position(const std::string& f, bool c960, Thread* t) { from_fen(f, c960, t); }
92 void operator=(const Position&);
95 void from_fen(const std::string& fen, bool isChess960, Thread* th);
96 const std::string to_fen() const;
97 void print(Move m = MOVE_NONE) const;
99 // Position representation
100 Bitboard pieces() const;
101 Bitboard pieces(Color c) const;
102 Bitboard pieces(PieceType pt) const;
103 Bitboard pieces(PieceType pt, Color c) const;
104 Bitboard pieces(PieceType pt1, PieceType pt2) const;
105 Bitboard pieces(PieceType pt1, PieceType pt2, Color c) const;
106 Piece piece_on(Square s) const;
107 Square king_square(Color c) const;
108 Square ep_square() const;
109 bool is_empty(Square s) const;
110 const Square* piece_list(Color c, PieceType pt) const;
111 int piece_count(Color c, PieceType pt) const;
114 int can_castle(CastleRight f) const;
115 int can_castle(Color c) const;
116 bool castle_impeded(Color c, CastlingSide s) const;
117 Square castle_rook_square(Color c, CastlingSide s) const;
120 bool in_check() const;
121 Bitboard checkers() const;
122 Bitboard discovered_check_candidates() const;
123 Bitboard pinned_pieces() const;
125 // Attacks to/from a given square
126 Bitboard attackers_to(Square s) const;
127 Bitboard attackers_to(Square s, Bitboard occ) const;
128 Bitboard attacks_from(Piece p, Square s) const;
129 static Bitboard attacks_from(Piece p, Square s, Bitboard occ);
130 template<PieceType> Bitboard attacks_from(Square s) const;
131 template<PieceType> Bitboard attacks_from(Square s, Color c) const;
133 // Properties of moves
134 bool move_gives_check(Move m, const CheckInfo& ci) const;
135 bool move_attacks_square(Move m, Square s) const;
136 bool pl_move_is_legal(Move m, Bitboard pinned) const;
137 bool is_pseudo_legal(const Move m) const;
138 bool is_capture(Move m) const;
139 bool is_capture_or_promotion(Move m) const;
140 bool is_passed_pawn_push(Move m) const;
141 Piece piece_moved(Move m) const;
142 PieceType captured_piece_type() const;
145 bool pawn_is_passed(Color c, Square s) const;
146 bool pawn_on_7th(Color c) const;
147 bool opposite_bishops() const;
148 bool bishop_pair(Color c) const;
150 // Doing and undoing moves
151 void do_move(Move m, StateInfo& st);
152 void do_move(Move m, StateInfo& st, const CheckInfo& ci, bool moveIsCheck);
153 void undo_move(Move m);
154 template<bool Do> void do_null_move(StateInfo& st);
156 // Static exchange evaluation
157 int see(Move m) const;
158 int see_sign(Move m) const;
160 // Accessing hash keys
162 Key exclusion_key() const;
163 Key pawn_key() const;
164 Key material_key() const;
166 // Incremental piece-square evaluation
167 Score psq_score() const;
168 Score psq_delta(Piece p, Square from, Square to) const;
169 Value non_pawn_material(Color c) const;
171 // Other properties of the position
172 Color side_to_move() const;
173 int startpos_ply_counter() const;
174 bool is_chess960() const;
175 Thread* this_thread() const;
176 int64_t nodes_searched() const;
177 void set_nodes_searched(int64_t n);
178 template<bool SkipRepetition> bool is_draw() const;
180 // Position consistency check, for debugging
181 bool pos_is_ok(int* failedStep = NULL) const;
184 // Global initialization
188 // Initialization helpers (used while setting up a position)
190 void put_piece(Piece p, Square s);
191 void set_castle_right(Color c, Square rfrom);
192 bool move_is_legal(const Move m) const;
194 // Helper template functions
195 template<bool Do> void do_castle_move(Move m);
196 template<bool FindPinned> Bitboard hidden_checkers() const;
198 // Computing hash keys from scratch (for initialization and debugging)
199 Key compute_key() const;
200 Key compute_pawn_key() const;
201 Key compute_material_key() const;
203 // Computing incremental evaluation scores and material counts
204 Score compute_psq_score() const;
205 Value compute_non_pawn_material(Color c) const;
208 Piece board[64]; // [square]
209 Bitboard byTypeBB[8]; // [pieceType]
210 Bitboard byColorBB[2]; // [color]
211 int pieceCount[2][8]; // [color][pieceType]
212 Square pieceList[2][8][16]; // [color][pieceType][index]
213 int index[64]; // [square]
216 int castleRightsMask[64]; // [square]
217 Square castleRookSquare[2][2]; // [color][side]
218 Bitboard castlePath[2][2]; // [color][side]
219 StateInfo startState;
228 static Score pieceSquareTable[16][64]; // [piece][square]
229 static Key zobrist[2][8][64]; // [color][pieceType][square]/[piece count]
230 static Key zobEp[8]; // [file]
231 static Key zobCastle[16]; // [castleRight]
232 static Key zobSideToMove;
233 static Key zobExclusion;
236 inline int64_t Position::nodes_searched() const {
240 inline void Position::set_nodes_searched(int64_t n) {
244 inline Piece Position::piece_on(Square s) const {
248 inline Piece Position::piece_moved(Move m) const {
249 return board[from_sq(m)];
252 inline bool Position::is_empty(Square s) const {
253 return board[s] == NO_PIECE;
256 inline Color Position::side_to_move() const {
260 inline Bitboard Position::pieces() const {
261 return byTypeBB[ALL_PIECES];
264 inline Bitboard Position::pieces(Color c) const {
268 inline Bitboard Position::pieces(PieceType pt) const {
272 inline Bitboard Position::pieces(PieceType pt, Color c) const {
273 return byTypeBB[pt] & byColorBB[c];
276 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2) const {
277 return byTypeBB[pt1] | byTypeBB[pt2];
280 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2, Color c) const {
281 return (byTypeBB[pt1] | byTypeBB[pt2]) & byColorBB[c];
284 inline int Position::piece_count(Color c, PieceType pt) const {
285 return pieceCount[c][pt];
288 inline const Square* Position::piece_list(Color c, PieceType pt) const {
289 return pieceList[c][pt];
292 inline Square Position::ep_square() const {
296 inline Square Position::king_square(Color c) const {
297 return pieceList[c][KING][0];
300 inline int Position::can_castle(CastleRight f) const {
301 return st->castleRights & f;
304 inline int Position::can_castle(Color c) const {
305 return st->castleRights & ((WHITE_OO | WHITE_OOO) << c);
308 inline bool Position::castle_impeded(Color c, CastlingSide s) const {
309 return byTypeBB[ALL_PIECES] & castlePath[c][s];
312 inline Square Position::castle_rook_square(Color c, CastlingSide s) const {
313 return castleRookSquare[c][s];
316 template<PieceType Pt>
317 inline Bitboard Position::attacks_from(Square s) const {
319 return Pt == BISHOP || Pt == ROOK ? attacks_bb<Pt>(s, pieces())
320 : Pt == QUEEN ? attacks_from<ROOK>(s) | attacks_from<BISHOP>(s)
321 : StepAttacksBB[Pt][s];
325 inline Bitboard Position::attacks_from<PAWN>(Square s, Color c) const {
326 return StepAttacksBB[make_piece(c, PAWN)][s];
329 inline Bitboard Position::attacks_from(Piece p, Square s) const {
330 return attacks_from(p, s, byTypeBB[ALL_PIECES]);
333 inline Bitboard Position::attackers_to(Square s) const {
334 return attackers_to(s, byTypeBB[ALL_PIECES]);
337 inline Bitboard Position::checkers() const {
338 return st->checkersBB;
341 inline bool Position::in_check() const {
342 return st->checkersBB != 0;
345 inline Bitboard Position::discovered_check_candidates() const {
346 return hidden_checkers<false>();
349 inline Bitboard Position::pinned_pieces() const {
350 return hidden_checkers<true>();
353 inline bool Position::pawn_is_passed(Color c, Square s) const {
354 return !(pieces(PAWN, ~c) & passed_pawn_mask(c, s));
357 inline Key Position::key() const {
361 inline Key Position::exclusion_key() const {
362 return st->key ^ zobExclusion;
365 inline Key Position::pawn_key() const {
369 inline Key Position::material_key() const {
370 return st->materialKey;
373 inline Score Position::psq_delta(Piece p, Square from, Square to) const {
374 return pieceSquareTable[p][to] - pieceSquareTable[p][from];
377 inline Score Position::psq_score() const {
381 inline Value Position::non_pawn_material(Color c) const {
382 return st->npMaterial[c];
385 inline bool Position::is_passed_pawn_push(Move m) const {
387 return type_of(piece_moved(m)) == PAWN
388 && pawn_is_passed(sideToMove, to_sq(m));
391 inline int Position::startpos_ply_counter() const {
392 return startPosPly + st->pliesFromNull; // HACK
395 inline bool Position::opposite_bishops() const {
397 return pieceCount[WHITE][BISHOP] == 1
398 && pieceCount[BLACK][BISHOP] == 1
399 && opposite_colors(pieceList[WHITE][BISHOP][0], pieceList[BLACK][BISHOP][0]);
402 inline bool Position::bishop_pair(Color c) const {
404 return pieceCount[c][BISHOP] >= 2
405 && opposite_colors(pieceList[c][BISHOP][0], pieceList[c][BISHOP][1]);
408 inline bool Position::pawn_on_7th(Color c) const {
409 return pieces(PAWN, c) & rank_bb(relative_rank(c, RANK_7));
412 inline bool Position::is_chess960() const {
416 inline bool Position::is_capture_or_promotion(Move m) const {
419 return is_special(m) ? !is_castle(m) : !is_empty(to_sq(m));
422 inline bool Position::is_capture(Move m) const {
424 // Note that castle is coded as "king captures the rook"
426 return (!is_empty(to_sq(m)) && !is_castle(m)) || is_enpassant(m);
429 inline PieceType Position::captured_piece_type() const {
430 return st->capturedType;
433 inline Thread* Position::this_thread() const {
437 #endif // !defined(POSITION_H_INCLUDED)