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;
63 struct ReducedStateInfo {
64 Key pawnKey, materialKey;
66 int castleRights, rule50, pliesFromNull;
72 /// The position data structure. A position consists of the following data:
74 /// * For each piece type, a bitboard representing the squares occupied
75 /// by pieces of that type.
76 /// * For each color, a bitboard representing the squares occupied by
77 /// pieces of that color.
78 /// * A bitboard of all occupied squares.
79 /// * A bitboard of all checking pieces.
80 /// * A 64-entry array of pieces, indexed by the squares of the board.
81 /// * The current side to move.
82 /// * Information about the castling rights for both sides.
83 /// * The initial files of the kings and both pairs of rooks. This is
84 /// used to implement the Chess960 castling rules.
85 /// * The en passant square (which is SQ_NONE if no en passant capture is
87 /// * The squares of the kings for both sides.
88 /// * Hash keys for the position itself, the current pawn structure, and
89 /// the current material situation.
90 /// * Hash keys for all previous positions in the game for detecting
92 /// * A counter for detecting 50 move rule draws.
97 Position(const Position& p, Thread* t) { *this = p; thisThread = t; }
98 Position(const std::string& f, bool c960, Thread* t) { from_fen(f, c960, t); }
99 Position& operator=(const Position&);
102 void from_fen(const std::string& fen, bool isChess960, Thread* th);
103 const std::string to_fen() const;
104 void print(Move m = MOVE_NONE) const;
106 // Position representation
107 Bitboard pieces() const;
108 Bitboard pieces(PieceType pt) const;
109 Bitboard pieces(PieceType pt1, PieceType pt2) const;
110 Bitboard pieces(Color c) const;
111 Bitboard pieces(Color c, PieceType pt) const;
112 Bitboard pieces(Color c, PieceType pt1, PieceType pt2) const;
113 Piece piece_on(Square s) const;
114 Square king_square(Color c) const;
115 Square ep_square() const;
116 bool is_empty(Square s) const;
117 const Square* piece_list(Color c, PieceType pt) const;
118 int piece_count(Color c, PieceType pt) const;
121 int can_castle(CastleRight f) const;
122 int can_castle(Color c) const;
123 bool castle_impeded(Color c, CastlingSide s) const;
124 Square castle_rook_square(Color c, CastlingSide s) const;
127 bool in_check() const;
128 Bitboard checkers() const;
129 Bitboard discovered_check_candidates() const;
130 Bitboard pinned_pieces() const;
132 // Attacks to/from a given square
133 Bitboard attackers_to(Square s) const;
134 Bitboard attackers_to(Square s, Bitboard occ) const;
135 Bitboard attacks_from(Piece p, Square s) const;
136 static Bitboard attacks_from(Piece p, Square s, Bitboard occ);
137 template<PieceType> Bitboard attacks_from(Square s) const;
138 template<PieceType> Bitboard attacks_from(Square s, Color c) const;
140 // Properties of moves
141 bool move_gives_check(Move m, const CheckInfo& ci) const;
142 bool move_attacks_square(Move m, Square s) const;
143 bool move_is_legal(const Move m) const;
144 bool pl_move_is_legal(Move m, Bitboard pinned) const;
145 bool is_pseudo_legal(const Move m) const;
146 bool is_capture(Move m) const;
147 bool is_capture_or_promotion(Move m) const;
148 bool is_passed_pawn_push(Move m) const;
149 Piece piece_moved(Move m) const;
150 PieceType captured_piece_type() const;
153 bool pawn_is_passed(Color c, Square s) const;
154 bool pawn_on_7th(Color c) const;
155 bool opposite_bishops() const;
156 bool bishop_pair(Color c) const;
158 // Doing and undoing moves
159 void do_move(Move m, StateInfo& st);
160 void do_move(Move m, StateInfo& st, const CheckInfo& ci, bool moveIsCheck);
161 void undo_move(Move m);
162 template<bool Do> void do_null_move(StateInfo& st);
164 // Static exchange evaluation
165 int see(Move m) const;
166 int see_sign(Move m) const;
168 // Accessing hash keys
170 Key exclusion_key() const;
171 Key pawn_key() const;
172 Key material_key() const;
174 // Incremental piece-square evaluation
175 Score psq_score() const;
176 Score psq_delta(Piece p, Square from, Square to) const;
177 Value non_pawn_material(Color c) const;
179 // Other properties of the position
180 Color side_to_move() const;
181 int startpos_ply_counter() const;
182 bool is_chess960() const;
183 Thread* this_thread() const;
184 int64_t nodes_searched() const;
185 void set_nodes_searched(int64_t n);
186 template<bool SkipRepetition> bool is_draw() const;
188 // Position consistency check, for debugging
189 bool pos_is_ok(int* failedStep = NULL) const;
192 // Global initialization
196 // Initialization helpers (used while setting up a position)
198 void put_piece(Piece p, Square s);
199 void set_castle_right(Color c, Square rfrom);
201 // Helper template functions
202 template<bool Do> void do_castle_move(Move m);
203 template<bool FindPinned> Bitboard hidden_checkers() const;
205 // Computing hash keys from scratch (for initialization and debugging)
206 Key compute_key() const;
207 Key compute_pawn_key() const;
208 Key compute_material_key() const;
210 // Computing incremental evaluation scores and material counts
211 Score compute_psq_score() const;
212 Value compute_non_pawn_material(Color c) const;
215 Piece board[64]; // [square]
216 Bitboard byTypeBB[8]; // [pieceType]
217 Bitboard byColorBB[2]; // [color]
218 int pieceCount[2][8]; // [color][pieceType]
219 Square pieceList[2][8][16]; // [color][pieceType][index]
220 int index[64]; // [square]
223 int castleRightsMask[64]; // [square]
224 Square castleRookSquare[2][2]; // [color][side]
225 Bitboard castlePath[2][2]; // [color][side]
226 StateInfo startState;
235 static Score pieceSquareTable[16][64]; // [piece][square]
236 static Key zobrist[2][8][64]; // [color][pieceType][square]/[piece count]
237 static Key zobEp[8]; // [file]
238 static Key zobCastle[16]; // [castleRight]
239 static Key zobSideToMove;
240 static Key zobExclusion;
243 inline int64_t Position::nodes_searched() const {
247 inline void Position::set_nodes_searched(int64_t n) {
251 inline Piece Position::piece_on(Square s) const {
255 inline Piece Position::piece_moved(Move m) const {
256 return board[from_sq(m)];
259 inline bool Position::is_empty(Square s) const {
260 return board[s] == NO_PIECE;
263 inline Color Position::side_to_move() const {
267 inline Bitboard Position::pieces() const {
268 return byTypeBB[ALL_PIECES];
271 inline Bitboard Position::pieces(PieceType pt) const {
275 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2) const {
276 return byTypeBB[pt1] | byTypeBB[pt2];
279 inline Bitboard Position::pieces(Color c) const {
283 inline Bitboard Position::pieces(Color c, PieceType pt) const {
284 return byColorBB[c] & byTypeBB[pt];
287 inline Bitboard Position::pieces(Color c, PieceType pt1, PieceType pt2) const {
288 return byColorBB[c] & (byTypeBB[pt1] | byTypeBB[pt2]);
291 inline int Position::piece_count(Color c, PieceType pt) const {
292 return pieceCount[c][pt];
295 inline const Square* Position::piece_list(Color c, PieceType pt) const {
296 return pieceList[c][pt];
299 inline Square Position::ep_square() const {
303 inline Square Position::king_square(Color c) const {
304 return pieceList[c][KING][0];
307 inline int Position::can_castle(CastleRight f) const {
308 return st->castleRights & f;
311 inline int Position::can_castle(Color c) const {
312 return st->castleRights & ((WHITE_OO | WHITE_OOO) << (2 * c));
315 inline bool Position::castle_impeded(Color c, CastlingSide s) const {
316 return byTypeBB[ALL_PIECES] & castlePath[c][s];
319 inline Square Position::castle_rook_square(Color c, CastlingSide s) const {
320 return castleRookSquare[c][s];
323 template<PieceType Pt>
324 inline Bitboard Position::attacks_from(Square s) const {
326 return Pt == BISHOP || Pt == ROOK ? attacks_bb<Pt>(s, pieces())
327 : Pt == QUEEN ? attacks_from<ROOK>(s) | attacks_from<BISHOP>(s)
328 : StepAttacksBB[Pt][s];
332 inline Bitboard Position::attacks_from<PAWN>(Square s, Color c) const {
333 return StepAttacksBB[make_piece(c, PAWN)][s];
336 inline Bitboard Position::attacks_from(Piece p, Square s) const {
337 return attacks_from(p, s, byTypeBB[ALL_PIECES]);
340 inline Bitboard Position::attackers_to(Square s) const {
341 return attackers_to(s, byTypeBB[ALL_PIECES]);
344 inline Bitboard Position::checkers() const {
345 return st->checkersBB;
348 inline bool Position::in_check() const {
349 return st->checkersBB != 0;
352 inline Bitboard Position::discovered_check_candidates() const {
353 return hidden_checkers<false>();
356 inline Bitboard Position::pinned_pieces() const {
357 return hidden_checkers<true>();
360 inline bool Position::pawn_is_passed(Color c, Square s) const {
361 return !(pieces(~c, PAWN) & passed_pawn_mask(c, s));
364 inline Key Position::key() const {
368 inline Key Position::exclusion_key() const {
369 return st->key ^ zobExclusion;
372 inline Key Position::pawn_key() const {
376 inline Key Position::material_key() const {
377 return st->materialKey;
380 inline Score Position::psq_delta(Piece p, Square from, Square to) const {
381 return pieceSquareTable[p][to] - pieceSquareTable[p][from];
384 inline Score Position::psq_score() const {
388 inline Value Position::non_pawn_material(Color c) const {
389 return st->npMaterial[c];
392 inline bool Position::is_passed_pawn_push(Move m) const {
394 return type_of(piece_moved(m)) == PAWN
395 && pawn_is_passed(sideToMove, to_sq(m));
398 inline int Position::startpos_ply_counter() const {
399 return startPosPly + st->pliesFromNull; // HACK
402 inline bool Position::opposite_bishops() const {
404 return pieceCount[WHITE][BISHOP] == 1
405 && pieceCount[BLACK][BISHOP] == 1
406 && opposite_colors(pieceList[WHITE][BISHOP][0], pieceList[BLACK][BISHOP][0]);
409 inline bool Position::bishop_pair(Color c) const {
411 return pieceCount[c][BISHOP] >= 2
412 && opposite_colors(pieceList[c][BISHOP][0], pieceList[c][BISHOP][1]);
415 inline bool Position::pawn_on_7th(Color c) const {
416 return pieces(c, PAWN) & rank_bb(relative_rank(c, RANK_7));
419 inline bool Position::is_chess960() const {
423 inline bool Position::is_capture_or_promotion(Move m) const {
426 return type_of(m) ? type_of(m) != CASTLE : !is_empty(to_sq(m));
429 inline bool Position::is_capture(Move m) const {
431 // Note that castle is coded as "king captures the rook"
433 return (!is_empty(to_sq(m)) && type_of(m) != CASTLE) || type_of(m) == ENPASSANT;
436 inline PieceType Position::captured_piece_type() const {
437 return st->capturedType;
440 inline Thread* Position::this_thread() const {
444 #endif // !defined(POSITION_H_INCLUDED)