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;
92 Square kingSquare[2], epSquare;
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, Bitboard& p) const;
189 Bitboard pinned_pieces(Color c) const;
191 // Checking pieces and under check information
192 Bitboard checkers() const;
193 bool is_check() const;
196 Square piece_list(Color c, PieceType pt, int index) const;
198 // Attack information for a given square
199 Bitboard attacks_to(Square s) const;
200 Bitboard attacks_to(Square s, Color c) const;
201 bool pawn_attacks_square(Color c, Square f, Square t) const;
202 Bitboard pawn_attacks(Color c, Square s) const;
205 Bitboard piece_attacks(Square s) const;
208 Bitboard piece_attacks_square(Square f, Square t) const; // Dispatch at compile-time
210 bool piece_attacks_square(Piece p, Square f, Square t) const; // Dispatch at run-time
212 // Properties of moves
213 bool pl_move_is_legal(Move m) const;
214 bool pl_move_is_legal(Move m, Bitboard pinned) const;
215 bool move_is_check(Move m) const;
216 bool move_is_check(Move m, Bitboard dcCandidates) const;
217 bool move_is_capture(Move m) const;
218 bool move_is_passed_pawn_push(Move m) const;
219 bool move_attacks_square(Move m, Square s) const;
221 // Information about pawns
222 bool pawn_is_passed(Color c, Square s) const;
223 static bool pawn_is_passed(Bitboard theirPawns, Color c, Square s);
224 static bool pawn_is_isolated(Bitboard ourPawns, Square s);
225 static bool pawn_is_doubled(Bitboard ourPawns, Color c, Square s);
228 bool square_is_weak(Square s, Color c) const;
230 // Doing and undoing moves
232 void do_move(Move m, StateInfo& st);
233 void do_move(Move m, StateInfo& st, Bitboard dcCandidates);
234 void undo_move(Move m);
235 void do_null_move(StateInfo& st);
236 void undo_null_move();
238 // Static exchange evaluation
239 int see(Square from, Square to) const;
240 int see(Move m) const;
241 int see(Square to) const;
242 int see_sign(Move m) const;
244 // Accessing hash keys
246 Key get_pawn_key() const;
247 Key get_material_key() const;
249 // Incremental evaluation
250 Value mg_value() const;
251 Value eg_value() const;
252 Value non_pawn_material(Color c) const;
253 Phase game_phase() const;
254 template<GamePhase> Value pst_delta(Piece piece, Square from, Square to) const;
256 // Game termination checks
257 bool is_mate() const;
258 bool is_draw() const;
260 // Check if one side threatens a mate in one
261 bool has_mate_threat(Color c);
263 // Number of plies since the last non-reversible move
264 int rule_50_counter() const;
266 // Other properties of the position
267 bool opposite_colored_bishops() const;
268 bool has_pawn_on_7th(Color c) const;
270 // Reset the gamePly variable to 0
271 void reset_game_ply();
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 allow_oo(Color c);
286 void allow_ooo(Color c);
288 // Helper functions for doing and undoing moves
289 void do_capture_move(Bitboard& key, PieceType capture, Color them, Square to, bool ep);
290 void do_castle_move(Move m);
291 void undo_castle_move(Move m);
292 void find_checkers();
294 template<PieceType Piece>
295 void update_checkers(Bitboard* pCheckersBB, Square ksq, Square from, Square to, Bitboard dcCandidates);
297 template<bool FindPinned>
298 Bitboard hidden_checkers(Color c) const;
300 // Computing hash keys from scratch (for initialization and debugging)
301 Key compute_key() const;
302 Key compute_pawn_key() const;
303 Key compute_material_key() const;
305 // Computing incremental evaluation scores and material counts
306 template<GamePhase> Value pst(Color c, PieceType pt, Square s) const;
307 template<GamePhase> Value compute_value() const;
308 Value compute_non_pawn_material(Color c) const;
311 Bitboard byColorBB[2], byTypeBB[8];
317 int pieceCount[2][8]; // [color][pieceType]
320 Square pieceList[2][8][16]; // [color][pieceType][index]
321 int index[64]; // [square]
326 Key history[MaxGameLength];
327 File initialKFile, initialKRFile, initialQRFile;
328 StateInfo startState;
332 static int castleRightsMask[64];
333 static Key zobrist[2][8][64];
334 static Key zobEp[64];
335 static Key zobCastle[16];
336 static Key zobMaterial[2][8][16];
337 static Key zobSideToMove;
338 static Value MgPieceSquareTable[16][64];
339 static Value EgPieceSquareTable[16][64];
344 //// Inline functions
347 inline Piece Position::piece_on(Square s) const {
351 inline Color Position::color_of_piece_on(Square s) const {
352 return color_of_piece(piece_on(s));
355 inline PieceType Position::type_of_piece_on(Square s) const {
356 return type_of_piece(piece_on(s));
359 inline bool Position::square_is_empty(Square s) const {
360 return piece_on(s) == EMPTY;
363 inline bool Position::square_is_occupied(Square s) const {
364 return !square_is_empty(s);
367 inline Value Position::midgame_value_of_piece_on(Square s) const {
368 return piece_value_midgame(piece_on(s));
371 inline Value Position::endgame_value_of_piece_on(Square s) const {
372 return piece_value_endgame(piece_on(s));
375 inline Color Position::side_to_move() const {
379 inline Bitboard Position::occupied_squares() const {
383 inline Bitboard Position::empty_squares() const {
384 return ~(occupied_squares());
387 inline Bitboard Position::pieces_of_color(Color c) const {
391 inline Bitboard Position::pieces(PieceType pt) const {
395 inline Bitboard Position::pieces(PieceType pt, Color c) const {
396 return byTypeBB[pt] & byColorBB[c];
399 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2) const {
400 return byTypeBB[pt1] | byTypeBB[pt2];
403 inline Bitboard Position::pieces(PieceType pt1, PieceType pt2, Color c) const {
404 return (byTypeBB[pt1] | byTypeBB[pt2]) & byColorBB[c];
407 inline int Position::piece_count(Color c, PieceType pt) const {
408 return pieceCount[c][pt];
411 inline Square Position::piece_list(Color c, PieceType pt, int index) const {
412 return pieceList[c][pt][index];
415 inline Square Position::ep_square() const {
419 inline Square Position::king_square(Color c) const {
420 return st->kingSquare[c];
423 inline bool Position::can_castle_kingside(Color side) const {
424 return st->castleRights & (1+int(side));
427 inline bool Position::can_castle_queenside(Color side) const {
428 return st->castleRights & (4+4*int(side));
431 inline bool Position::can_castle(Color side) const {
432 return can_castle_kingside(side) || can_castle_queenside(side);
435 inline Square Position::initial_kr_square(Color c) const {
436 return relative_square(c, make_square(initialKRFile, RANK_1));
439 inline Square Position::initial_qr_square(Color c) const {
440 return relative_square(c, make_square(initialQRFile, RANK_1));
443 inline Bitboard Position::pawn_attacks(Color c, Square s) const {
444 return StepAttackBB[piece_of_color_and_type(c, PAWN)][s];
447 template<PieceType Piece> // Knight and King
448 inline Bitboard Position::piece_attacks(Square s) const {
449 return StepAttackBB[Piece][s];
453 inline Bitboard Position::piece_attacks<PAWN>(Square s) const {
454 return StepAttackBB[WP][s] | StepAttackBB[BP][s];
458 inline Bitboard Position::piece_attacks<BISHOP>(Square s) const {
459 return bishop_attacks_bb(s, occupied_squares());
463 inline Bitboard Position::piece_attacks<ROOK>(Square s) const {
464 return rook_attacks_bb(s, occupied_squares());
468 inline Bitboard Position::piece_attacks<QUEEN>(Square s) const {
469 return piece_attacks<ROOK>(s) | piece_attacks<BISHOP>(s);
472 inline Bitboard Position::checkers() const {
473 return st->checkersBB;
476 inline bool Position::is_check() const {
477 return st->checkersBB != EmptyBoardBB;
480 inline bool Position::pawn_attacks_square(Color c, Square f, Square t) const {
481 return bit_is_set(pawn_attacks(c, f), t);
484 template<PieceType Piece>
485 inline Bitboard Position::piece_attacks_square(Square f, Square t) const {
486 return bit_is_set(piece_attacks<Piece>(f), t);
489 inline Bitboard Position::attacks_to(Square s, Color c) const {
491 return attacks_to(s) & pieces_of_color(c);
494 inline bool Position::pawn_is_passed(Color c, Square s) const {
495 return !(pieces(PAWN, opposite_color(c)) & passed_pawn_mask(c, s));
498 inline bool Position::pawn_is_passed(Bitboard theirPawns, Color c, Square s) {
499 return !(theirPawns & passed_pawn_mask(c, s));
502 inline bool Position::pawn_is_isolated(Bitboard ourPawns, Square s) {
503 return !(ourPawns & neighboring_files_bb(s));
506 inline bool Position::pawn_is_doubled(Bitboard ourPawns, Color c, Square s) {
507 return ourPawns & squares_behind(c, s);
510 inline bool Position::square_is_weak(Square s, Color c) const {
511 return !(pieces(PAWN, c) & outpost_mask(opposite_color(c), s));
514 inline Key Position::get_key() const {
518 inline Key Position::get_pawn_key() const {
522 inline Key Position::get_material_key() const {
523 return st->materialKey;
526 template<Position::GamePhase Ph>
527 inline Value Position::pst(Color c, PieceType pt, Square s) const {
528 return (Ph == MidGame ? MgPieceSquareTable[piece_of_color_and_type(c, pt)][s]
529 : EgPieceSquareTable[piece_of_color_and_type(c, pt)][s]);
532 template<Position::GamePhase Ph>
533 inline Value Position::pst_delta(Piece piece, Square from, Square to) const {
534 return (Ph == MidGame ? MgPieceSquareTable[piece][to] - MgPieceSquareTable[piece][from]
535 : EgPieceSquareTable[piece][to] - EgPieceSquareTable[piece][from]);
538 inline Value Position::mg_value() const {
542 inline Value Position::eg_value() const {
546 inline Value Position::non_pawn_material(Color c) const {
547 return st->npMaterial[c];
550 inline Phase Position::game_phase() const {
552 // Values modified by Joona Kiiski
553 static const Value MidgameLimit = Value(15581);
554 static const Value EndgameLimit = Value(3998);
556 Value npm = non_pawn_material(WHITE) + non_pawn_material(BLACK);
558 if (npm >= MidgameLimit)
559 return PHASE_MIDGAME;
560 else if(npm <= EndgameLimit)
561 return PHASE_ENDGAME;
563 return Phase(((npm - EndgameLimit) * 128) / (MidgameLimit - EndgameLimit));
566 inline bool Position::move_is_passed_pawn_push(Move m) const {
568 Color c = side_to_move();
569 return piece_on(move_from(m)) == piece_of_color_and_type(c, PAWN)
570 && pawn_is_passed(c, move_to(m));
573 inline int Position::rule_50_counter() const {
578 inline bool Position::opposite_colored_bishops() const {
580 return piece_count(WHITE, BISHOP) == 1
581 && piece_count(BLACK, BISHOP) == 1
582 && square_color(piece_list(WHITE, BISHOP, 0)) != square_color(piece_list(BLACK, BISHOP, 0));
585 inline bool Position::has_pawn_on_7th(Color c) const {
587 return pieces(PAWN, c) & relative_rank_bb(c, RANK_7);
590 inline bool Position::move_is_capture(Move m) const {
592 // Move must not be MOVE_NONE !
594 return (!square_is_empty(move_to(m)) && !move_is_castle(m)) || move_is_ep(m);
597 #endif // !defined(POSITION_H_INCLUDED)