2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2009 Marco Costalba
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
24 // Disable some silly and noisy warning from MSVC compiler
27 // Forcing value to bool 'true' or 'false' (performance warning)
28 #pragma warning(disable: 4800)
30 // Conditional expression is constant
31 #pragma warning(disable: 4127)
42 #include "direction.h"
53 /// FEN string for the initial position
54 const std::string StartPosition = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1";
56 /// Maximum number of plies per game (220 should be enough, because the
57 /// maximum search depth is 100, and during position setup we reset the
58 /// move counter for every non-reversible move).
59 const int MaxGameLength = 220;
66 /// Castle rights, encoded as bit fields
84 /// The StateInfo struct stores information we need to restore a Position
85 /// object to its previous state when we retract a move. Whenever a move
86 /// is made on the board (by calling Position::do_move), an StateInfo object
87 /// must be passed as a parameter.
90 Key key, pawnKey, materialKey;
91 int castleRights, rule50, pliesFromNull;
93 Value mgValue, egValue;
102 /// The position data structure. A position consists of the following data:
104 /// * For each piece type, a bitboard representing the squares occupied
105 /// by pieces of that type.
106 /// * For each color, a bitboard representing the squares occupied by
107 /// pieces of that color.
108 /// * A bitboard of all occupied squares.
109 /// * A bitboard of all checking pieces.
110 /// * A 64-entry array of pieces, indexed by the squares of the board.
111 /// * The current side to move.
112 /// * Information about the castling rights for both sides.
113 /// * The initial files of the kings and both pairs of rooks. This is
114 /// used to implement the Chess960 castling rules.
115 /// * The en passant square (which is SQ_NONE if no en passant capture is
117 /// * The squares of the kings for both sides.
118 /// * Hash keys for the position itself, the current pawn structure, and
119 /// the current material situation.
120 /// * Hash keys for all previous positions in the game for detecting
121 /// repetition draws.
122 /// * A counter for detecting 50 move rule draws.
126 friend class MaterialInfo;
127 friend class EndgameFunctions;
137 Position(const Position& pos);
138 Position(const std::string& fen);
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 copy(const Position& pos);
147 void flipped_copy(const Position& pos);
149 // The piece on a given square
150 Piece piece_on(Square s) const;
151 PieceType type_of_piece_on(Square s) const;
152 Color color_of_piece_on(Square s) const;
153 bool square_is_empty(Square s) const;
154 bool square_is_occupied(Square s) const;
155 Value midgame_value_of_piece_on(Square s) const;
156 Value endgame_value_of_piece_on(Square s) const;
159 Color side_to_move() const;
161 // Bitboard representation of the position
162 Bitboard empty_squares() const;
163 Bitboard occupied_squares() const;
164 Bitboard pieces_of_color(Color c) const;
165 Bitboard pieces(PieceType pt) const;
166 Bitboard pieces(PieceType pt, Color c) const;
167 Bitboard pieces(PieceType pt1, PieceType pt2) const;
168 Bitboard pieces(PieceType pt1, PieceType pt2, Color c) const;
170 // Number of pieces of each color and type
171 int piece_count(Color c, PieceType pt) const;
173 // The en passant square
174 Square ep_square() const;
176 // Current king position for each color
177 Square king_square(Color c) const;
180 bool can_castle_kingside(Color c) const;
181 bool can_castle_queenside(Color c) const;
182 bool can_castle(Color c) const;
183 Square initial_kr_square(Color c) const;
184 Square initial_qr_square(Color c) const;
186 // Bitboards for pinned pieces and discovered check candidates
187 Bitboard discovered_check_candidates(Color c) const;
188 Bitboard pinned_pieces(Color c) const;
190 // Checking pieces and under check information
191 Bitboard checkers() const;
192 bool is_check() const;
195 Square piece_list(Color c, PieceType pt, int index) const;
196 const Square* piece_list_begin(Color c, PieceType pt) const;
198 // Information about attacks to or from a given square
199 Bitboard attackers_to(Square s) const;
200 Bitboard attacks_from(Piece p, Square s) const;
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, Bitboard dcCandidates) 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 // Information about pawns
215 bool pawn_is_passed(Color c, Square s) const;
216 static bool pawn_is_passed(Bitboard theirPawns, Color c, Square s);
217 static bool pawn_is_isolated(Bitboard ourPawns, Square s);
218 static bool pawn_is_doubled(Bitboard ourPawns, Color c, Square s);
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, Bitboard dcCandidates);
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(Square to) const;
235 int see_sign(Move m) const;
237 // Accessing hash keys
239 Key get_pawn_key() const;
240 Key get_material_key() const;
242 // Incremental evaluation
243 Value mg_value() const;
244 Value eg_value() const;
245 Value non_pawn_material(Color c) const;
246 Phase game_phase() const;
247 template<GamePhase> Value pst_delta(Piece piece, Square from, Square to) const;
249 // Game termination checks
250 bool is_mate() const;
251 bool is_draw() const;
253 // Check if one side threatens a mate in one
254 bool has_mate_threat(Color c);
256 // Number of plies since the last non-reversible move
257 int rule_50_counter() const;
259 // Other properties of the position
260 bool opposite_colored_bishops() const;
261 bool has_pawn_on_7th(Color c) const;
263 // Reset the gamePly variable to 0
264 void reset_game_ply();
266 // Position consistency check, for debugging
267 bool is_ok(int* failedStep = NULL) const;
269 // Static member functions
270 static void init_zobrist();
271 static void init_piece_square_tables();
275 // Initialization helper functions (used while setting up a position)
277 void put_piece(Piece p, Square s);
278 void allow_oo(Color c);
279 void allow_ooo(Color c);
281 // Helper functions for doing and undoing moves
282 void do_capture_move(Bitboard& key, PieceType capture, Color them, Square to, bool ep);
283 void do_castle_move(Move m);
284 void undo_castle_move(Move m);
285 void find_checkers();
287 template<PieceType Piece>
288 void update_checkers(Bitboard* pCheckersBB, Square ksq, Square from, Square to, Bitboard dcCandidates);
290 template<bool FindPinned>
291 Bitboard hidden_checkers(Color c) const;
293 // Computing hash keys from scratch (for initialization and debugging)
294 Key compute_key() const;
295 Key compute_pawn_key() const;
296 Key compute_material_key() const;
298 // Computing incremental evaluation scores and material counts
299 template<GamePhase> Value pst(Color c, PieceType pt, Square s) const;
300 template<GamePhase> Value compute_value() const;
301 Value compute_non_pawn_material(Color c) const;
307 Bitboard byTypeBB[8], byColorBB[2];
310 int pieceCount[2][8]; // [color][pieceType]
313 Square pieceList[2][8][16]; // [color][pieceType][index]
314 int index[64]; // [square]
319 Key history[MaxGameLength];
320 File initialKFile, initialKRFile, initialQRFile;
321 StateInfo startState;
325 static int castleRightsMask[64];
326 static Key zobrist[2][8][64];
327 static Key zobEp[64];
328 static Key zobCastle[16];
329 static Key zobMaterial[2][8][16];
330 static Key zobSideToMove;
331 static Value MgPieceSquareTable[16][64];
332 static Value EgPieceSquareTable[16][64];
337 //// Inline functions
340 inline Piece Position::piece_on(Square s) const {
344 inline Color Position::color_of_piece_on(Square s) const {
345 return color_of_piece(piece_on(s));
348 inline PieceType Position::type_of_piece_on(Square s) const {
349 return type_of_piece(piece_on(s));
352 inline bool Position::square_is_empty(Square s) const {
353 return piece_on(s) == EMPTY;
356 inline bool Position::square_is_occupied(Square s) const {
357 return !square_is_empty(s);
360 inline Value Position::midgame_value_of_piece_on(Square s) const {
361 return piece_value_midgame(piece_on(s));
364 inline Value Position::endgame_value_of_piece_on(Square s) const {
365 return piece_value_endgame(piece_on(s));
368 inline Color Position::side_to_move() const {
372 inline Bitboard Position::occupied_squares() const {
376 inline Bitboard Position::empty_squares() const {
377 return ~(occupied_squares());
380 inline Bitboard Position::pieces_of_color(Color c) const {
384 inline Bitboard Position::pieces(PieceType pt) const {
388 inline Bitboard Position::pieces(PieceType pt, Color c) const {
389 return byTypeBB[pt] & byColorBB[c];
392 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2) const {
393 return byTypeBB[pt1] | byTypeBB[pt2];
396 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2, Color c) const {
397 return (byTypeBB[pt1] | byTypeBB[pt2]) & byColorBB[c];
400 inline int Position::piece_count(Color c, PieceType pt) const {
401 return pieceCount[c][pt];
404 inline Square Position::piece_list(Color c, PieceType pt, int index) const {
405 return pieceList[c][pt][index];
408 inline const Square* Position::piece_list_begin(Color c, PieceType pt) const {
409 return pieceList[c][pt];
412 inline Square Position::ep_square() const {
416 inline Square Position::king_square(Color c) const {
417 return pieceList[c][KING][0];
420 inline bool Position::can_castle_kingside(Color side) const {
421 return st->castleRights & (1+int(side));
424 inline bool Position::can_castle_queenside(Color side) const {
425 return st->castleRights & (4+4*int(side));
428 inline bool Position::can_castle(Color side) const {
429 return can_castle_kingside(side) || can_castle_queenside(side);
432 inline Square Position::initial_kr_square(Color c) const {
433 return relative_square(c, make_square(initialKRFile, RANK_1));
436 inline Square Position::initial_qr_square(Color c) const {
437 return relative_square(c, make_square(initialQRFile, RANK_1));
441 inline Bitboard Position::attacks_from<PAWN>(Square s, Color c) const {
442 return StepAttackBB[piece_of_color_and_type(c, PAWN)][s];
445 template<PieceType Piece> // Knight and King and white pawns
446 inline Bitboard Position::attacks_from(Square s) const {
447 return StepAttackBB[Piece][s];
451 inline Bitboard Position::attacks_from<BISHOP>(Square s) const {
452 return bishop_attacks_bb(s, occupied_squares());
456 inline Bitboard Position::attacks_from<ROOK>(Square s) const {
457 return rook_attacks_bb(s, occupied_squares());
461 inline Bitboard Position::attacks_from<QUEEN>(Square s) const {
462 return attacks_from<ROOK>(s) | attacks_from<BISHOP>(s);
465 inline Bitboard Position::checkers() const {
466 return st->checkersBB;
469 inline bool Position::is_check() const {
470 return st->checkersBB != EmptyBoardBB;
473 inline bool Position::pawn_is_passed(Color c, Square s) const {
474 return !(pieces(PAWN, opposite_color(c)) & passed_pawn_mask(c, s));
477 inline bool Position::pawn_is_passed(Bitboard theirPawns, Color c, Square s) {
478 return !(theirPawns & passed_pawn_mask(c, s));
481 inline bool Position::pawn_is_isolated(Bitboard ourPawns, Square s) {
482 return !(ourPawns & neighboring_files_bb(s));
485 inline bool Position::pawn_is_doubled(Bitboard ourPawns, Color c, Square s) {
486 return ourPawns & squares_behind(c, s);
489 inline bool Position::square_is_weak(Square s, Color c) const {
490 return !(pieces(PAWN, c) & outpost_mask(opposite_color(c), s));
493 inline Key Position::get_key() const {
497 inline Key Position::get_pawn_key() const {
501 inline Key Position::get_material_key() const {
502 return st->materialKey;
505 template<Position::GamePhase Ph>
506 inline Value Position::pst(Color c, PieceType pt, Square s) const {
507 return (Ph == MidGame ? MgPieceSquareTable[piece_of_color_and_type(c, pt)][s]
508 : EgPieceSquareTable[piece_of_color_and_type(c, pt)][s]);
511 template<Position::GamePhase Ph>
512 inline Value Position::pst_delta(Piece piece, Square from, Square to) const {
513 return (Ph == MidGame ? MgPieceSquareTable[piece][to] - MgPieceSquareTable[piece][from]
514 : EgPieceSquareTable[piece][to] - EgPieceSquareTable[piece][from]);
517 inline Value Position::mg_value() const {
521 inline Value Position::eg_value() const {
525 inline Value Position::non_pawn_material(Color c) const {
526 return st->npMaterial[c];
529 inline Phase Position::game_phase() const {
531 // Values modified by Joona Kiiski
532 static const Value MidgameLimit = Value(15581);
533 static const Value EndgameLimit = Value(3998);
535 Value npm = non_pawn_material(WHITE) + non_pawn_material(BLACK);
537 if (npm >= MidgameLimit)
538 return PHASE_MIDGAME;
539 else if(npm <= EndgameLimit)
540 return PHASE_ENDGAME;
542 return Phase(((npm - EndgameLimit) * 128) / (MidgameLimit - EndgameLimit));
545 inline bool Position::move_is_passed_pawn_push(Move m) const {
547 Color c = side_to_move();
548 return piece_on(move_from(m)) == piece_of_color_and_type(c, PAWN)
549 && pawn_is_passed(c, move_to(m));
552 inline int Position::rule_50_counter() const {
557 inline bool Position::opposite_colored_bishops() const {
559 return piece_count(WHITE, BISHOP) == 1
560 && piece_count(BLACK, BISHOP) == 1
561 && square_color(piece_list(WHITE, BISHOP, 0)) != square_color(piece_list(BLACK, BISHOP, 0));
564 inline bool Position::has_pawn_on_7th(Color c) const {
566 return pieces(PAWN, c) & relative_rank_bb(c, RANK_7);
569 inline bool Position::move_is_capture(Move m) const {
571 // Move must not be MOVE_NONE !
572 return (m & (3 << 15)) ? !move_is_castle(m) : !square_is_empty(move_to(m));
575 inline bool Position::move_is_capture_or_promotion(Move m) const {
577 // Move must not be MOVE_NONE !
578 return (m & (0x1F << 12)) ? !move_is_castle(m) : !square_is_empty(move_to(m));
581 #endif // !defined(POSITION_H_INCLUDED)