2 Glaurung, a UCI chess playing engine.
3 Copyright (C) 2004-2008 Tord Romstad
5 Glaurung is free software: you can redistribute it and/or modify
6 it under the terms of the GNU General Public License as published by
7 the Free Software Foundation, either version 3 of the License, or
8 (at your option) any later version.
10 Glaurung is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 GNU General Public License for more details.
15 You should have received a copy of the GNU General Public License
16 along with this program. If not, see <http://www.gnu.org/licenses/>.
20 #if !defined(POSITION_H_INCLUDED)
21 #define POSITION_H_INCLUDED
23 // Disable a silly and noisy warning from MSVC compiler
26 // Forcing value to bool 'true' or 'false' (performance warning)
27 #pragma warning(disable: 4800)
\r
37 #include "direction.h"
49 /// FEN string for the initial position:
50 const std::string StartPosition =
51 "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1";
53 /// Maximum number of plies per game (220 should be enough, because the
54 /// maximum search depth is 100, and during position setup we reset the
55 /// move counter for every non-reversible move):
56 const int MaxGameLength = 220;
63 /// Castle rights, encoded as bit fields:
75 /// The UndoInfo struct stores information we need to restore a Position
76 /// object to its previous state when we retract a move. Whenever a move
77 /// is made on the board (by calling Position::do_move), an UndoInfo object
78 /// must be passed as a parameter. When the move is unmade (by calling
79 /// Position::undo_move), the same UndoInfo object must be passed again.
85 Key key, pawnKey, materialKey;
89 Value mgValue, egValue;
93 /// The position data structure. A position consists of the following data:
95 /// * For each piece type, a bitboard representing the squares occupied
96 /// by pieces of that type.
97 /// * For each color, a bitboard representing the squares occupiecd by
98 /// pieces of that color.
99 /// * A bitboard of all occupied squares.
100 /// * A bitboard of all checking pieces.
101 /// * A 64-entry array of pieces, indexed by the squares of the board.
102 /// * The current side to move.
103 /// * Information about the castling rights for both sides.
104 /// * The initial files of the kings and both pairs of rooks. This is
105 /// used to implement the Chess960 castling rules.
106 /// * The en passant square (which is SQ_NONE if no en passant capture is
108 /// * The squares of the kings for both sides.
109 /// * The last move played.
110 /// * Hash keys for the position itself, the current pawn structure, and
111 /// the current material situation.
112 /// * Hash keys for all previous positions in the game (for detecting
113 /// repetition draws.
114 /// * A counter for detecting 50 move rule draws.
118 friend class MaterialInfo;
123 Position(const Position &pos);
124 Position(const std::string &fen);
127 void from_fen(const std::string &fen);
128 const std::string to_fen() const;
132 void copy(const Position &pos);
133 void flipped_copy(const Position &pos);
135 // The piece on a given square
136 Piece piece_on(Square s) const;
137 PieceType type_of_piece_on(Square s) const;
138 Color color_of_piece_on(Square s) const;
139 bool square_is_empty(Square s) const;
140 bool square_is_occupied(Square s) const;
141 Value midgame_value_of_piece_on(Square s) const;
142 Value endgame_value_of_piece_on(Square s) const;
145 Color side_to_move() const;
147 // Bitboard representation of the position
148 Bitboard empty_squares() const;
149 Bitboard occupied_squares() const;
150 Bitboard pieces_of_color(Color c) const;
151 Bitboard pieces_of_type(PieceType pt) const;
152 Bitboard pieces_of_color_and_type(Color c, PieceType pt) const;
153 Bitboard pawns() const;
154 Bitboard knights() const;
155 Bitboard bishops() const;
156 Bitboard rooks() const;
157 Bitboard queens() const;
158 Bitboard kings() const;
159 Bitboard rooks_and_queens() const;
160 Bitboard bishops_and_queens() const;
161 Bitboard sliders() const;
162 Bitboard pawns(Color c) const;
163 Bitboard knights(Color c) const;
164 Bitboard bishops(Color c) const;
165 Bitboard rooks(Color c) const;
166 Bitboard queens(Color c) const;
167 Bitboard kings(Color c) const;
168 Bitboard rooks_and_queens(Color c) const;
169 Bitboard bishops_and_queens(Color c) const;
170 Bitboard sliders_of_color(Color c) const;
172 // Number of pieces of each color and type
173 int piece_count(Color c, PieceType pt) const;
175 // The en passant square:
176 Square ep_square() const;
178 // Current king position for each color
179 Square king_square(Color c) const;
182 bool can_castle_kingside(Color c) const;
183 bool can_castle_queenside(Color c) const;
184 bool can_castle(Color c) const;
185 Square initial_kr_square(Color c) const;
186 Square initial_qr_square(Color c) const;
189 Bitboard sliding_attacks(Square s, Direction d) const;
190 Bitboard ray_attacks(Square s, SignedDirection d) const;
191 Bitboard pawn_attacks(Color c, Square s) const;
194 Bitboard piece_attacks(Square s) const;
196 // Bitboards for pinned pieces and discovered check candidates
197 Bitboard discovered_check_candidates(Color c) const;
198 Bitboard pinned_pieces(Color c) const;
201 Bitboard checkers() const;
204 Square piece_list(Color c, PieceType pt, int index) const;
206 // Attack information for a given square
207 bool square_is_attacked(Square s, Color c) const;
208 Bitboard attacks_to(Square s) const;
209 Bitboard attacks_to(Square s, Color c) const;
210 bool is_check() const;
211 bool pawn_attacks_square(Color c, Square f, Square t) const;
214 Bitboard piece_attacks_square(Square f, Square t) const; // Dispatch at compile-time
216 bool piece_attacks_square(Square f, Square t) const; // Dispatch at run-time
218 // Properties of moves
219 bool move_is_legal(Move m) const;
220 bool move_is_legal(Move m, Bitboard pinned) const;
221 bool move_is_check(Move m) const;
222 bool move_is_check(Move m, Bitboard dcCandidates) const;
223 bool move_is_capture(Move m) const;
224 bool move_is_deep_pawn_push(Move m) const;
225 bool move_is_pawn_push_to_7th(Move m) const;
226 bool move_is_passed_pawn_push(Move m) const;
227 bool move_was_passed_pawn_push(Move m) const;
228 bool move_attacks_square(Move m, Square s) const;
230 // Information about pawns
231 bool pawn_is_passed(Color c, Square s) const;
232 bool pawn_is_isolated(Color c, Square s) const;
233 bool pawn_is_doubled(Color c, Square s) const;
235 // Open and half-open files
236 bool file_is_open(File f) const;
237 bool file_is_half_open(Color c, File f) const;
240 bool square_is_weak(Square s, Color c) const;
242 // Doing and undoing moves
243 void backup(UndoInfo &u) const;
244 void restore(const UndoInfo &u);
245 void do_move(Move m, UndoInfo &u);
246 void do_move(Move m, UndoInfo &u, Bitboard dcCandidates);
247 void undo_move(Move m, const UndoInfo &u);
248 void do_null_move(UndoInfo &u);
249 void undo_null_move(const UndoInfo &u);
251 // Static exchange evaluation
252 int see(Square from, Square to) const;
253 int see(Move m) const;
255 // Accessing hash keys
257 Key get_pawn_key() const;
258 Key get_material_key() const;
260 // Incremental evaluation
261 Value mg_value() const;
262 Value eg_value() const;
263 Value non_pawn_material(Color c) const;
264 Phase game_phase() const;
265 Value mg_pst_delta(Move m) const;
267 // Game termination checks
269 bool is_draw() const;
271 // Check if one side threatens a mate in one
272 bool has_mate_threat(Color c);
274 // Number of plies since the last non-reversible move
275 int rule_50_counter() const;
277 // Other properties of the position
278 bool opposite_colored_bishops() const;
279 bool has_pawn_on_7th(Color c) const;
281 // Reset the gamePly variable to 0
282 void reset_game_ply();
284 // Position consistency check, for debugging
285 bool is_ok(int* failedStep = NULL) const;
287 // Static member functions:
288 static void init_zobrist();
289 static void init_piece_square_tables();
292 // Initialization helper functions (used while setting up a position)
294 void put_piece(Piece p, Square s);
295 void allow_oo(Color c);
296 void allow_ooo(Color c);
298 // Helper functions for doing and undoing moves
299 void do_castle_move(Move m);
300 void do_promotion_move(Move m, UndoInfo &u);
301 void do_ep_move(Move m);
302 void undo_castle_move(Move m);
303 void undo_promotion_move(Move m, const UndoInfo &u);
304 void undo_ep_move(Move m);
305 void find_checkers();
307 // Computing hash keys from scratch (for initialization and debugging)
308 Key compute_key() const;
309 Key compute_pawn_key() const;
310 Key compute_material_key() const;
312 // Computing incremental evaluation scores and material counts
313 Value mg_pst(Color c, PieceType pt, Square s) const;
314 Value eg_pst(Color c, PieceType pt, Square s) const;
315 Value compute_mg_value() const;
316 Value compute_eg_value() const;
317 Value compute_non_pawn_material(Color c) const;
320 Bitboard byColorBB[2], byTypeBB[8];
327 int pieceCount[2][8]; // [color][pieceType]
330 Square pieceList[2][8][16]; // [color][pieceType][index]
336 File initialKFile, initialKRFile, initialQRFile;
338 Square kingSquare[2];
340 Key key, pawnKey, materialKey, history[MaxGameLength];
342 Value mgValue, egValue;
346 static int castleRightsMask[64];
347 static Key zobrist[2][8][64];
348 static Key zobEp[64];
349 static Key zobCastle[16];
350 static Key zobMaterial[2][8][16];
351 static Key zobSideToMove;
352 static Value MgPieceSquareTable[16][64];
353 static Value EgPieceSquareTable[16][64];
358 //// Inline functions
361 inline Piece Position::piece_on(Square s) const {
365 inline Color Position::color_of_piece_on(Square s) const {
366 return color_of_piece(piece_on(s));
369 inline PieceType Position::type_of_piece_on(Square s) const {
370 return type_of_piece(piece_on(s));
373 inline bool Position::square_is_empty(Square s) const {
374 return piece_on(s) == EMPTY;
377 inline bool Position::square_is_occupied(Square s) const {
378 return !square_is_empty(s);
381 inline Value Position::midgame_value_of_piece_on(Square s) const {
382 return piece_value_midgame(piece_on(s));
385 inline Value Position::endgame_value_of_piece_on(Square s) const {
386 return piece_value_endgame(piece_on(s));
389 inline Color Position::side_to_move() const {
393 inline Bitboard Position::occupied_squares() const {
397 inline Bitboard Position::empty_squares() const {
398 return ~(occupied_squares());
401 inline Bitboard Position::pieces_of_color(Color c) const {
405 inline Bitboard Position::pieces_of_type(PieceType pt) const {
409 inline Bitboard Position::pieces_of_color_and_type(Color c, PieceType pt) const {
410 return pieces_of_color(c) & pieces_of_type(pt);
413 inline Bitboard Position::pawns() const {
414 return pieces_of_type(PAWN);
417 inline Bitboard Position::knights() const {
418 return pieces_of_type(KNIGHT);
421 inline Bitboard Position::bishops() const {
422 return pieces_of_type(BISHOP);
425 inline Bitboard Position::rooks() const {
426 return pieces_of_type(ROOK);
429 inline Bitboard Position::queens() const {
430 return pieces_of_type(QUEEN);
433 inline Bitboard Position::kings() const {
434 return pieces_of_type(KING);
437 inline Bitboard Position::rooks_and_queens() const {
438 return rooks() | queens();
441 inline Bitboard Position::bishops_and_queens() const {
442 return bishops() | queens();
445 inline Bitboard Position::sliders() const {
446 return bishops() | queens() | rooks();
449 inline Bitboard Position::pawns(Color c) const {
450 return pieces_of_color_and_type(c, PAWN);
453 inline Bitboard Position::knights(Color c) const {
454 return pieces_of_color_and_type(c, KNIGHT);
457 inline Bitboard Position::bishops(Color c) const {
458 return pieces_of_color_and_type(c, BISHOP);
461 inline Bitboard Position::rooks(Color c) const {
462 return pieces_of_color_and_type(c, ROOK);
465 inline Bitboard Position::queens(Color c) const {
466 return pieces_of_color_and_type(c, QUEEN);
469 inline Bitboard Position::kings(Color c) const {
470 return pieces_of_color_and_type(c, KING);
473 inline Bitboard Position::rooks_and_queens(Color c) const {
474 return rooks_and_queens() & pieces_of_color(c);
477 inline Bitboard Position::bishops_and_queens(Color c) const {
478 return bishops_and_queens() & pieces_of_color(c);
481 inline Bitboard Position::sliders_of_color(Color c) const {
482 return sliders() & pieces_of_color(c);
485 inline int Position::piece_count(Color c, PieceType pt) const {
486 return pieceCount[c][pt];
489 inline Square Position::piece_list(Color c, PieceType pt, int index) const {
490 return pieceList[c][pt][index];
493 inline Square Position::ep_square() const {
497 inline Square Position::king_square(Color c) const {
498 return kingSquare[c];
501 inline bool Position::can_castle_kingside(Color side) const {
502 return castleRights & (1+int(side));
505 inline bool Position::can_castle_queenside(Color side) const {
506 return castleRights & (4+4*int(side));
509 inline bool Position::can_castle(Color side) const {
510 return can_castle_kingside(side) || can_castle_queenside(side);
513 inline Square Position::initial_kr_square(Color c) const {
514 return relative_square(c, make_square(initialKRFile, RANK_1));
517 inline Square Position::initial_qr_square(Color c) const {
518 return relative_square(c, make_square(initialQRFile, RANK_1));
521 inline Bitboard Position::pawn_attacks(Color c, Square s) const {
522 return StepAttackBB[pawn_of_color(c)][s];
526 inline Bitboard Position::piece_attacks<KNIGHT>(Square s) const {
527 return StepAttackBB[KNIGHT][s];
531 inline Bitboard Position::piece_attacks<BISHOP>(Square s) const {
532 return bishop_attacks_bb(s, occupied_squares());
536 inline Bitboard Position::piece_attacks<ROOK>(Square s) const {
537 return rook_attacks_bb(s, occupied_squares());
541 inline Bitboard Position::piece_attacks<QUEEN>(Square s) const {
542 return piece_attacks<ROOK>(s) | piece_attacks<BISHOP>(s);
546 inline Bitboard Position::piece_attacks<KING>(Square s) const {
547 return StepAttackBB[KING][s];
550 inline Bitboard Position::checkers() const {
554 inline bool Position::is_check() const {
555 return checkers() != EmptyBoardBB;
558 inline bool Position::pawn_attacks_square(Color c, Square f, Square t) const {
559 return bit_is_set(pawn_attacks(c, f), t);
562 template<PieceType Piece>
563 Bitboard Position::piece_attacks_square(Square f, Square t) const {
564 return bit_is_set(piece_attacks<Piece>(f), t);
567 inline bool Position::pawn_is_passed(Color c, Square s) const {
568 return !(pawns(opposite_color(c)) & passed_pawn_mask(c, s));
571 inline bool Position::pawn_is_isolated(Color c, Square s) const {
572 return !(pawns(c) & neighboring_files_bb(s));
575 inline bool Position::pawn_is_doubled(Color c, Square s) const {
576 return pawns(c) & squares_behind(c, s);
579 inline bool Position::file_is_open(File f) const {
580 return !(pawns() & file_bb(f));
583 inline bool Position::file_is_half_open(Color c, File f) const {
584 return !(pawns(c) & file_bb(f));
587 inline bool Position::square_is_weak(Square s, Color c) const {
588 return !(pawns(c) & outpost_mask(opposite_color(c), s));
591 inline Key Position::get_key() const {
595 inline Key Position::get_pawn_key() const {
599 inline Key Position::get_material_key() const {
603 inline Value Position::mg_pst(Color c, PieceType pt, Square s) const {
604 return MgPieceSquareTable[piece_of_color_and_type(c, pt)][s];
607 inline Value Position::mg_pst_delta(Move m) const {
608 return MgPieceSquareTable[piece_on(move_from(m))][move_to(m)]
609 -MgPieceSquareTable[piece_on(move_from(m))][move_from(m)];
612 inline Value Position::eg_pst(Color c, PieceType pt, Square s) const {
613 return EgPieceSquareTable[piece_of_color_and_type(c, pt)][s];
616 inline Value Position::mg_value() const {
620 inline Value Position::eg_value() const {
624 inline Value Position::non_pawn_material(Color c) const {
625 return npMaterial[c];
628 inline Phase Position::game_phase() const {
630 // The purpose of the Value(325) terms below is to make sure the difference
631 // between MidgameLimit and EndgameLimit is a power of 2, which should make
632 // the division at the end of the function a bit faster.
633 static const Value MidgameLimit = 2 * QueenValueMidgame
634 + 2 * RookValueMidgame
635 + 6 * BishopValueMidgame
638 static const Value EndgameLimit = 4 * RookValueMidgame - Value(325);
640 Value npm = non_pawn_material(WHITE) + non_pawn_material(BLACK);
642 if (npm >= MidgameLimit)
643 return PHASE_MIDGAME;
644 else if(npm <= EndgameLimit)
645 return PHASE_ENDGAME;
647 return Phase(((npm - EndgameLimit) * 128) / (MidgameLimit - EndgameLimit));
650 inline bool Position::move_is_deep_pawn_push(Move m) const {
652 Color c = side_to_move();
653 return piece_on(move_from(m)) == pawn_of_color(c)
654 && relative_rank(c, move_to(m)) > RANK_4;
657 inline bool Position::move_is_pawn_push_to_7th(Move m) const {
659 Color c = side_to_move();
660 return piece_on(move_from(m)) == pawn_of_color(c)
661 && relative_rank(c, move_to(m)) == RANK_7;
664 inline bool Position::move_is_passed_pawn_push(Move m) const {
666 Color c = side_to_move();
667 return piece_on(move_from(m)) == pawn_of_color(c)
668 && pawn_is_passed(c, move_to(m));
671 inline bool Position::move_was_passed_pawn_push(Move m) const {
673 Color c = opposite_color(side_to_move());
674 return piece_on(move_to(m)) == pawn_of_color(c)
675 && pawn_is_passed(c, move_to(m));
678 inline int Position::rule_50_counter() const {
683 inline bool Position::opposite_colored_bishops() const {
685 return piece_count(WHITE, BISHOP) == 1
686 && piece_count(BLACK, BISHOP) == 1
687 && square_color(piece_list(WHITE, BISHOP, 0)) != square_color(piece_list(BLACK, BISHOP, 0));
690 inline bool Position::has_pawn_on_7th(Color c) const {
692 return pawns(c) & relative_rank_bb(c, RANK_7);
696 #endif // !defined(POSITION_H_INCLUDED)