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/>.
21 #if !defined(POSITION_H_INCLUDED)
22 #define POSITION_H_INCLUDED
30 #include "direction.h"
41 /// Maximum number of plies per game (220 should be enough, because the
42 /// maximum search depth is 100, and during position setup we reset the
43 /// move counter for every non-reversible move).
44 const int MaxGameLength = 220;
51 /// struct checkInfo is initialized at c'tor time and keeps
52 /// info used to detect if a move gives check.
56 explicit CheckInfo(const Position&);
58 Bitboard dcCandidates;
63 /// Castle rights, encoded as bit fields
81 /// The StateInfo struct stores information we need to restore a Position
82 /// object to its previous state when we retract a move. Whenever a move
83 /// is made on the board (by calling Position::do_move), an StateInfo object
84 /// must be passed as a parameter.
87 Key pawnKey, materialKey;
88 int castleRights, rule50, gamePly, pliesFromNull;
93 PieceType capturedType;
100 /// The position data structure. A position consists of the following data:
102 /// * For each piece type, a bitboard representing the squares occupied
103 /// by pieces of that type.
104 /// * For each color, a bitboard representing the squares occupied by
105 /// pieces of that color.
106 /// * A bitboard of all occupied squares.
107 /// * A bitboard of all checking pieces.
108 /// * A 64-entry array of pieces, indexed by the squares of the board.
109 /// * The current side to move.
110 /// * Information about the castling rights for both sides.
111 /// * The initial files of the kings and both pairs of rooks. This is
112 /// used to implement the Chess960 castling rules.
113 /// * The en passant square (which is SQ_NONE if no en passant capture is
115 /// * The squares of the kings for both sides.
116 /// * Hash keys for the position itself, the current pawn structure, and
117 /// the current material situation.
118 /// * Hash keys for all previous positions in the game for detecting
119 /// repetition draws.
120 /// * A counter for detecting 50 move rule draws.
124 friend class MaterialInfo;
125 friend class EndgameFunctions;
127 Position(); // No default or copy c'tor allowed
128 Position(const Position& pos);
137 Position(const Position& pos, int threadID);
138 Position(const std::string& fen, int threadID);
141 void from_fen(const std::string& fen);
142 const std::string to_fen() const;
143 void print(Move m = MOVE_NONE) const;
146 void flipped_copy(const Position& pos);
148 // The piece on a given square
149 Piece piece_on(Square s) const;
150 PieceType type_of_piece_on(Square s) const;
151 Color color_of_piece_on(Square s) const;
152 bool square_is_empty(Square s) const;
153 bool square_is_occupied(Square s) const;
154 Value midgame_value_of_piece_on(Square s) const;
155 Value endgame_value_of_piece_on(Square s) const;
158 Color side_to_move() const;
160 // Bitboard representation of the position
161 Bitboard empty_squares() const;
162 Bitboard occupied_squares() const;
163 Bitboard pieces_of_color(Color c) const;
164 Bitboard pieces(PieceType pt) const;
165 Bitboard pieces(PieceType pt, Color c) const;
166 Bitboard pieces(PieceType pt1, PieceType pt2) const;
167 Bitboard pieces(PieceType pt1, PieceType pt2, Color c) const;
169 // Number of pieces of each color and type
170 int piece_count(Color c, PieceType pt) const;
172 // The en passant square
173 Square ep_square() const;
175 // Current king position for each color
176 Square king_square(Color c) const;
179 bool can_castle_kingside(Color c) const;
180 bool can_castle_queenside(Color c) const;
181 bool can_castle(Color c) const;
182 Square initial_kr_square(Color c) const;
183 Square initial_qr_square(Color c) const;
185 // Bitboards for pinned pieces and discovered check candidates
186 Bitboard discovered_check_candidates(Color c) const;
187 Bitboard pinned_pieces(Color c) const;
189 // Checking pieces and under check information
190 Bitboard checkers() const;
191 bool is_check() const;
194 Square piece_list(Color c, PieceType pt, int index) const;
195 const Square* piece_list_begin(Color c, PieceType pt) const;
197 // Information about attacks to or from a given square
198 Bitboard attackers_to(Square s) const;
199 Bitboard attacks_from(Piece p, Square s) const;
200 static Bitboard attacks_from(Piece p, Square s, Bitboard occ);
201 template<PieceType> Bitboard attacks_from(Square s) const;
202 template<PieceType> Bitboard attacks_from(Square s, Color c) const;
204 // Properties of moves
205 bool pl_move_is_legal(Move m, Bitboard pinned) const;
206 bool pl_move_is_evasion(Move m, Bitboard pinned) const;
207 bool move_is_check(Move m) const;
208 bool move_is_check(Move m, const CheckInfo& ci) const;
209 bool move_is_capture(Move m) const;
210 bool move_is_capture_or_promotion(Move m) const;
211 bool move_is_passed_pawn_push(Move m) const;
212 bool move_attacks_square(Move m, Square s) const;
214 // Piece captured with previous moves
215 PieceType captured_piece_type() const;
217 // Information about pawns
218 bool pawn_is_passed(Color c, Square s) const;
221 bool square_is_weak(Square s, Color c) const;
223 // Doing and undoing moves
225 void do_move(Move m, StateInfo& st);
226 void do_move(Move m, StateInfo& st, const CheckInfo& ci, bool moveIsCheck);
227 void undo_move(Move m);
228 void do_null_move(StateInfo& st);
229 void undo_null_move();
231 // Static exchange evaluation
232 int see(Square from, Square to) const;
233 int see(Move m) const;
234 int see_sign(Move m) const;
236 // Accessing hash keys
238 Key get_exclusion_key() const;
239 Key get_pawn_key() const;
240 Key get_material_key() const;
242 // Incremental evaluation
244 Value non_pawn_material(Color c) const;
245 static Score pst_delta(Piece piece, Square from, Square to);
247 // Game termination checks
248 bool is_mate() const;
249 bool is_draw() const;
251 // Check if side to move could be mated in one
252 bool has_mate_threat();
254 // Number of plies since the last non-reversible move
255 int rule_50_counter() const;
257 int startpos_ply_counter() const;
259 // Other properties of the position
260 bool opposite_colored_bishops() const;
261 bool has_pawn_on_7th(Color c) const;
262 bool is_chess960() const;
264 // Current thread ID searching on the position
267 // Reset the gamePly variable to 0
268 void reset_game_ply();
269 void inc_startpos_ply_counter();
270 int64_t nodes_searched() const;
271 void set_nodes_searched(int64_t n);
273 // Position consistency check, for debugging
274 bool is_ok(int* failedStep = NULL) const;
276 // Static member functions
277 static void init_zobrist();
278 static void init_piece_square_tables();
282 // Initialization helper functions (used while setting up a position)
284 void put_piece(Piece p, Square s);
285 void do_allow_oo(Color c);
286 void do_allow_ooo(Color c);
287 bool set_castling_rights(char token);
289 // Helper functions for doing and undoing moves
290 void do_capture_move(Key& key, PieceType capture, Color them, Square to, bool ep);
291 void do_castle_move(Move m);
292 void undo_castle_move(Move m);
293 void find_checkers();
295 template<bool FindPinned>
296 Bitboard hidden_checkers(Color c) const;
298 // Computing hash keys from scratch (for initialization and debugging)
299 Key compute_key() const;
300 Key compute_pawn_key() const;
301 Key compute_material_key() const;
303 // Computing incremental evaluation scores and material counts
304 static Score pst(Color c, PieceType pt, Square s);
305 Score compute_value() const;
306 Value compute_non_pawn_material(Color c) const;
312 Bitboard byTypeBB[8], byColorBB[2];
315 int pieceCount[2][8]; // [color][pieceType]
318 Square pieceList[2][8][16]; // [color][pieceType][index]
319 int index[64]; // [square]
323 Key history[MaxGameLength];
324 int castleRightsMask[64];
325 StateInfo startState;
326 File initialKFile, initialKRFile, initialQRFile;
328 int startPosPlyCounter;
334 static Key zobrist[2][8][64];
335 static Key zobEp[64];
336 static Key zobCastle[16];
337 static Key zobSideToMove;
338 static Score PieceSquareTable[16][64];
339 static Key zobExclusion;
340 static const Value seeValues[8];
341 static const Value PieceValueMidgame[17];
342 static const Value PieceValueEndgame[17];
347 //// Inline functions
350 inline int64_t Position::nodes_searched() const {
354 inline void Position::set_nodes_searched(int64_t n) {
358 inline Piece Position::piece_on(Square s) const {
362 inline Color Position::color_of_piece_on(Square s) const {
363 return color_of_piece(piece_on(s));
366 inline PieceType Position::type_of_piece_on(Square s) const {
367 return type_of_piece(piece_on(s));
370 inline bool Position::square_is_empty(Square s) const {
371 return piece_on(s) == PIECE_NONE;
374 inline bool Position::square_is_occupied(Square s) const {
375 return !square_is_empty(s);
378 inline Value Position::midgame_value_of_piece_on(Square s) const {
379 return PieceValueMidgame[piece_on(s)];
382 inline Value Position::endgame_value_of_piece_on(Square s) const {
383 return PieceValueEndgame[piece_on(s)];
386 inline Color Position::side_to_move() const {
390 inline Bitboard Position::occupied_squares() const {
394 inline Bitboard Position::empty_squares() const {
395 return ~occupied_squares();
398 inline Bitboard Position::pieces_of_color(Color c) const {
402 inline Bitboard Position::pieces(PieceType pt) const {
406 inline Bitboard Position::pieces(PieceType pt, Color c) const {
407 return byTypeBB[pt] & byColorBB[c];
410 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2) const {
411 return byTypeBB[pt1] | byTypeBB[pt2];
414 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2, Color c) const {
415 return (byTypeBB[pt1] | byTypeBB[pt2]) & byColorBB[c];
418 inline int Position::piece_count(Color c, PieceType pt) const {
419 return pieceCount[c][pt];
422 inline Square Position::piece_list(Color c, PieceType pt, int idx) const {
423 return pieceList[c][pt][idx];
426 inline const Square* Position::piece_list_begin(Color c, PieceType pt) const {
427 return pieceList[c][pt];
430 inline Square Position::ep_square() const {
434 inline Square Position::king_square(Color c) const {
435 return pieceList[c][KING][0];
438 inline bool Position::can_castle_kingside(Color side) const {
439 return st->castleRights & (1+int(side));
442 inline bool Position::can_castle_queenside(Color side) const {
443 return st->castleRights & (4+4*int(side));
446 inline bool Position::can_castle(Color side) const {
447 return can_castle_kingside(side) || can_castle_queenside(side);
450 inline Square Position::initial_kr_square(Color c) const {
451 return relative_square(c, make_square(initialKRFile, RANK_1));
454 inline Square Position::initial_qr_square(Color c) const {
455 return relative_square(c, make_square(initialQRFile, RANK_1));
459 inline Bitboard Position::attacks_from<PAWN>(Square s, Color c) const {
460 return StepAttackBB[piece_of_color_and_type(c, PAWN)][s];
463 template<PieceType Piece> // Knight and King and white pawns
464 inline Bitboard Position::attacks_from(Square s) const {
465 return StepAttackBB[Piece][s];
469 inline Bitboard Position::attacks_from<BISHOP>(Square s) const {
470 return bishop_attacks_bb(s, occupied_squares());
474 inline Bitboard Position::attacks_from<ROOK>(Square s) const {
475 return rook_attacks_bb(s, occupied_squares());
479 inline Bitboard Position::attacks_from<QUEEN>(Square s) const {
480 return attacks_from<ROOK>(s) | attacks_from<BISHOP>(s);
483 inline Bitboard Position::checkers() const {
484 return st->checkersBB;
487 inline bool Position::is_check() const {
488 return st->checkersBB != EmptyBoardBB;
491 inline bool Position::pawn_is_passed(Color c, Square s) const {
492 return !(pieces(PAWN, opposite_color(c)) & passed_pawn_mask(c, s));
495 inline bool Position::square_is_weak(Square s, Color c) const {
496 return !(pieces(PAWN, opposite_color(c)) & attack_span_mask(c, s));
499 inline Key Position::get_key() const {
503 inline Key Position::get_exclusion_key() const {
504 return st->key ^ zobExclusion;
507 inline Key Position::get_pawn_key() const {
511 inline Key Position::get_material_key() const {
512 return st->materialKey;
515 inline Score Position::pst(Color c, PieceType pt, Square s) {
516 return PieceSquareTable[piece_of_color_and_type(c, pt)][s];
519 inline Score Position::pst_delta(Piece piece, Square from, Square to) {
520 return PieceSquareTable[piece][to] - PieceSquareTable[piece][from];
523 inline Score Position::value() const {
527 inline Value Position::non_pawn_material(Color c) const {
528 return st->npMaterial[c];
531 inline bool Position::move_is_passed_pawn_push(Move m) const {
533 Color c = side_to_move();
534 return piece_on(move_from(m)) == piece_of_color_and_type(c, PAWN)
535 && pawn_is_passed(c, move_to(m));
538 inline int Position::rule_50_counter() const {
542 inline int Position::startpos_ply_counter() const {
543 return startPosPlyCounter;
546 inline bool Position::opposite_colored_bishops() const {
548 return piece_count(WHITE, BISHOP) == 1
549 && piece_count(BLACK, BISHOP) == 1
550 && !same_color_squares(piece_list(WHITE, BISHOP, 0), piece_list(BLACK, BISHOP, 0));
553 inline bool Position::has_pawn_on_7th(Color c) const {
554 return pieces(PAWN, c) & relative_rank_bb(c, RANK_7);
557 inline bool Position::is_chess960() const {
561 inline bool Position::move_is_capture(Move m) const {
563 // Move must not be MOVE_NONE !
564 return (m & (3 << 15)) ? !move_is_castle(m) : !square_is_empty(move_to(m));
567 inline bool Position::move_is_capture_or_promotion(Move m) const {
569 // Move must not be MOVE_NONE !
570 return (m & (0x1F << 12)) ? !move_is_castle(m) : !square_is_empty(move_to(m));
573 inline PieceType Position::captured_piece_type() const {
574 return st->capturedType;
577 inline int Position::thread() const {
581 inline void Position::do_allow_oo(Color c) {
582 st->castleRights |= (1 + int(c));
585 inline void Position::do_allow_ooo(Color c) {
586 st->castleRights |= (4 + 4*int(c));
589 #endif // !defined(POSITION_H_INCLUDED)