2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2013 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 #ifndef POSITION_H_INCLUDED
21 #define POSITION_H_INCLUDED
30 /// The checkInfo struct is initialized at c'tor time and keeps info used
31 /// to detect if a move gives check.
37 explicit CheckInfo(const Position&);
39 Bitboard dcCandidates;
41 Bitboard checkSq[PIECE_TYPE_NB];
46 /// The StateInfo struct stores information needed to restore a Position
47 /// object to its previous state when we retract a move. Whenever a move
48 /// is made on the board (by calling Position::do_move), a StateInfo
49 /// object must be passed as a parameter.
52 Key pawnKey, materialKey;
53 Value npMaterial[COLOR_NB];
54 int castleRights, rule50, pliesFromNull;
60 PieceType capturedType;
65 /// When making a move the current StateInfo up to 'key' excluded is copied to
66 /// the new one. Here we calculate the quad words (64bits) needed to be copied.
67 const size_t StateCopySize64 = offsetof(StateInfo, key) / sizeof(uint64_t) + 1;
70 /// The Position class stores the information regarding the board representation
71 /// like pieces, side to move, hash keys, castling info, etc. The most important
72 /// methods are do_move() and undo_move(), used by the search to update node info
73 /// when traversing the search tree.
78 Position(const Position& p, Thread* t) { *this = p; thisThread = t; }
79 Position(const std::string& f, bool c960, Thread* t) { set(f, c960, t); }
80 Position& operator=(const Position&);
84 void set(const std::string& fen, bool isChess960, Thread* th);
85 const std::string fen() const;
86 const std::string pretty(Move m = MOVE_NONE) const;
88 // Position representation
89 Bitboard pieces() const;
90 Bitboard pieces(PieceType pt) const;
91 Bitboard pieces(PieceType pt1, PieceType pt2) const;
92 Bitboard pieces(Color c) const;
93 Bitboard pieces(Color c, PieceType pt) const;
94 Bitboard pieces(Color c, PieceType pt1, PieceType pt2) const;
95 Piece piece_on(Square s) const;
96 Square king_square(Color c) const;
97 Square ep_square() const;
98 bool empty(Square s) const;
99 template<PieceType Pt> int count(Color c) const;
100 template<PieceType Pt> const Square* list(Color c) const;
103 int can_castle(CastleRight f) const;
104 int can_castle(Color c) const;
105 bool castle_impeded(Color c, CastlingSide s) const;
106 Square castle_rook_square(Color c, CastlingSide s) const;
109 Bitboard checkers() const;
110 Bitboard discovered_check_candidates() const;
111 Bitboard pinned_pieces() const;
113 // Attacks to/from a given square
114 Bitboard attackers_to(Square s) const;
115 Bitboard attackers_to(Square s, Bitboard occ) const;
116 Bitboard attacks_from(Piece p, Square s) const;
117 static Bitboard attacks_from(Piece p, Square s, Bitboard occ);
118 template<PieceType> Bitboard attacks_from(Square s) const;
119 template<PieceType> Bitboard attacks_from(Square s, Color c) const;
121 // Properties of moves
122 bool legal(Move m, Bitboard pinned) const;
123 bool pseudo_legal(const Move m) const;
124 bool capture(Move m) const;
125 bool capture_or_promotion(Move m) const;
126 bool gives_check(Move m, const CheckInfo& ci) const;
127 bool passed_pawn_push(Move m) const;
128 Piece moved_piece(Move m) const;
129 PieceType captured_piece_type() const;
132 bool pawn_passed(Color c, Square s) const;
133 bool pawn_on_7th(Color c) const;
134 bool bishop_pair(Color c) const;
135 bool opposite_bishops() const;
137 // Doing and undoing moves
138 void do_move(Move m, StateInfo& st);
139 void do_move(Move m, StateInfo& st, const CheckInfo& ci, bool moveIsCheck);
140 void undo_move(Move m);
141 void do_null_move(StateInfo& st);
142 void undo_null_move();
144 // Static exchange evaluation
145 int see(Move m, int asymmThreshold = 0) const;
146 int see_sign(Move m) const;
148 // Accessing hash keys
150 Key exclusion_key() const;
151 Key pawn_key() const;
152 Key material_key() const;
154 // Incremental piece-square evaluation
155 Score psq_score() const;
156 Value non_pawn_material(Color c) const;
158 // Other properties of the position
159 Color side_to_move() const;
160 int game_ply() const;
161 bool is_chess960() const;
162 Thread* this_thread() const;
163 int64_t nodes_searched() const;
164 void set_nodes_searched(int64_t n);
165 bool is_draw() const;
167 // Position consistency check, for debugging
168 bool pos_is_ok(int* failedStep = NULL) const;
172 // Initialization helpers (used while setting up a position)
174 void set_castle_right(Color c, Square rfrom);
177 void do_castle(Square kfrom, Square kto, Square rfrom, Square rto);
178 Bitboard hidden_checkers(Square ksq, Color c) const;
179 void put_piece(Square s, Color c, PieceType pt);
180 void remove_piece(Square s, Color c, PieceType pt);
181 void move_piece(Square from, Square to, Color c, PieceType pt);
183 // Computing hash keys from scratch (for initialization and debugging)
184 Key compute_key() const;
185 Key compute_pawn_key() const;
186 Key compute_material_key() const;
188 // Computing incremental evaluation scores and material counts
189 Score compute_psq_score() const;
190 Value compute_non_pawn_material(Color c) const;
193 Piece board[SQUARE_NB];
194 Bitboard byTypeBB[PIECE_TYPE_NB];
195 Bitboard byColorBB[COLOR_NB];
196 int pieceCount[COLOR_NB][PIECE_TYPE_NB];
197 Square pieceList[COLOR_NB][PIECE_TYPE_NB][16];
198 int index[SQUARE_NB];
201 int castleRightsMask[SQUARE_NB];
202 Square castleRookSquare[COLOR_NB][CASTLING_SIDE_NB];
203 Bitboard castlePath[COLOR_NB][CASTLING_SIDE_NB];
204 StateInfo startState;
213 inline int64_t Position::nodes_searched() const {
217 inline void Position::set_nodes_searched(int64_t n) {
221 inline Piece Position::piece_on(Square s) const {
225 inline Piece Position::moved_piece(Move m) const {
226 return board[from_sq(m)];
229 inline bool Position::empty(Square s) const {
230 return board[s] == NO_PIECE;
233 inline Color Position::side_to_move() const {
237 inline Bitboard Position::pieces() const {
238 return byTypeBB[ALL_PIECES];
241 inline Bitboard Position::pieces(PieceType pt) const {
245 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2) const {
246 return byTypeBB[pt1] | byTypeBB[pt2];
249 inline Bitboard Position::pieces(Color c) const {
253 inline Bitboard Position::pieces(Color c, PieceType pt) const {
254 return byColorBB[c] & byTypeBB[pt];
257 inline Bitboard Position::pieces(Color c, PieceType pt1, PieceType pt2) const {
258 return byColorBB[c] & (byTypeBB[pt1] | byTypeBB[pt2]);
261 template<PieceType Pt> inline int Position::count(Color c) const {
262 return pieceCount[c][Pt];
265 template<PieceType Pt> inline const Square* Position::list(Color c) const {
266 return pieceList[c][Pt];
269 inline Square Position::ep_square() const {
273 inline Square Position::king_square(Color c) const {
274 return pieceList[c][KING][0];
277 inline int Position::can_castle(CastleRight f) const {
278 return st->castleRights & f;
281 inline int Position::can_castle(Color c) const {
282 return st->castleRights & ((WHITE_OO | WHITE_OOO) << (2 * c));
285 inline bool Position::castle_impeded(Color c, CastlingSide s) const {
286 return byTypeBB[ALL_PIECES] & castlePath[c][s];
289 inline Square Position::castle_rook_square(Color c, CastlingSide s) const {
290 return castleRookSquare[c][s];
293 template<PieceType Pt>
294 inline Bitboard Position::attacks_from(Square s) const {
296 return Pt == BISHOP || Pt == ROOK ? attacks_bb<Pt>(s, pieces())
297 : Pt == QUEEN ? attacks_from<ROOK>(s) | attacks_from<BISHOP>(s)
298 : StepAttacksBB[Pt][s];
302 inline Bitboard Position::attacks_from<PAWN>(Square s, Color c) const {
303 return StepAttacksBB[make_piece(c, PAWN)][s];
306 inline Bitboard Position::attacks_from(Piece p, Square s) const {
307 return attacks_from(p, s, byTypeBB[ALL_PIECES]);
310 inline Bitboard Position::attackers_to(Square s) const {
311 return attackers_to(s, byTypeBB[ALL_PIECES]);
314 inline Bitboard Position::checkers() const {
315 return st->checkersBB;
318 inline Bitboard Position::discovered_check_candidates() const {
319 return hidden_checkers(king_square(~sideToMove), sideToMove);
322 inline Bitboard Position::pinned_pieces() const {
323 return hidden_checkers(king_square(sideToMove), ~sideToMove);
326 inline bool Position::pawn_passed(Color c, Square s) const {
327 return !(pieces(~c, PAWN) & passed_pawn_mask(c, s));
330 inline bool Position::passed_pawn_push(Move m) const {
332 return type_of(moved_piece(m)) == PAWN
333 && pawn_passed(sideToMove, to_sq(m));
336 inline Key Position::key() const {
340 inline Key Position::pawn_key() const {
344 inline Key Position::material_key() const {
345 return st->materialKey;
348 inline Score Position::psq_score() const {
352 inline Value Position::non_pawn_material(Color c) const {
353 return st->npMaterial[c];
356 inline int Position::game_ply() const {
360 inline bool Position::opposite_bishops() const {
362 return pieceCount[WHITE][BISHOP] == 1
363 && pieceCount[BLACK][BISHOP] == 1
364 && opposite_colors(pieceList[WHITE][BISHOP][0], pieceList[BLACK][BISHOP][0]);
367 inline bool Position::bishop_pair(Color c) const {
369 return pieceCount[c][BISHOP] >= 2
370 && opposite_colors(pieceList[c][BISHOP][0], pieceList[c][BISHOP][1]);
373 inline bool Position::pawn_on_7th(Color c) const {
374 return pieces(c, PAWN) & rank_bb(relative_rank(c, RANK_7));
377 inline bool Position::is_chess960() const {
381 inline bool Position::capture_or_promotion(Move m) const {
384 return type_of(m) ? type_of(m) != CASTLE : !empty(to_sq(m));
387 inline bool Position::capture(Move m) const {
389 // Note that castle is coded as "king captures the rook"
391 return (!empty(to_sq(m)) && type_of(m) != CASTLE) || type_of(m) == ENPASSANT;
394 inline PieceType Position::captured_piece_type() const {
395 return st->capturedType;
398 inline Thread* Position::this_thread() const {
402 inline void Position::put_piece(Square s, Color c, PieceType pt) {
404 board[s] = make_piece(c, pt);
405 byTypeBB[ALL_PIECES] |= s;
408 index[s] = pieceCount[c][pt]++;
409 pieceList[c][pt][index[s]] = s;
412 inline void Position::move_piece(Square from, Square to, Color c, PieceType pt) {
414 // index[from] is not updated and becomes stale. This works as long
415 // as index[] is accessed just by known occupied squares.
416 Bitboard from_to_bb = SquareBB[from] ^ SquareBB[to];
417 byTypeBB[ALL_PIECES] ^= from_to_bb;
418 byTypeBB[pt] ^= from_to_bb;
419 byColorBB[c] ^= from_to_bb;
420 board[from] = NO_PIECE;
421 board[to] = make_piece(c, pt);
422 index[to] = index[from];
423 pieceList[c][pt][index[to]] = to;
426 inline void Position::remove_piece(Square s, Color c, PieceType pt) {
428 // WARNING: This is not a reversible operation. If we remove a piece in
429 // do_move() and then replace it in undo_move() we will put it at the end of
430 // the list and not in its original place, it means index[] and pieceList[]
431 // are not guaranteed to be invariant to a do_move() + undo_move() sequence.
432 byTypeBB[ALL_PIECES] ^= s;
435 /* board[s] = NO_PIECE; */ // Not needed, will be overwritten by capturing
436 Square lastSquare = pieceList[c][pt][--pieceCount[c][pt]];
437 index[lastSquare] = index[s];
438 pieceList[c][pt][index[lastSquare]] = lastSquare;
439 pieceList[c][pt][pieceCount[c][pt]] = SQ_NONE;
442 #endif // #ifndef POSITION_H_INCLUDED