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
29 #include "direction.h"
41 /// FEN string for the initial position:
42 const std::string StartPosition =
43 "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1";
45 /// Maximum number of plies per game (220 should be enough, because the
46 /// maximum search depth is 100, and during position setup we reset the
47 /// move counter for every non-reversible move):
48 const int MaxGameLength = 220;
55 /// Castle rights, encoded as bit fields:
59 WHITE_OO = 1, BLACK_OO = 2,
60 WHITE_OOO = 4, BLACK_OOO = 8,
65 /// The UndoInfo struct stores information we need to restore a Position
66 /// object to its previous state when we retract a move. Whenever a move
67 /// is made on the board (by calling Position::do_move), an UndoInfo object
68 /// must be passed as a parameter. When the move is unmade (by calling
69 /// Position::undo_move), the same UndoInfo object must be passed again.
75 Key key, pawnKey, materialKey;
79 Value mgValue, egValue;
83 /// The position data structure. A position consists of the following data:
85 /// * For each piece type, a bitboard representing the squares occupied
86 /// by pieces of that type.
87 /// * For each color, a bitboard representing the squares occupiecd by
88 /// pieces of that color.
89 /// * A bitboard of all occupied squares.
90 /// * A bitboard of all checking pieces.
91 /// * A 64-entry array of pieces, indexed by the squares of the board.
92 /// * The current side to move.
93 /// * Information about the castling rights for both sides.
94 /// * The initial files of the kings and both pairs of rooks. This is
95 /// used to implement the Chess960 castling rules.
96 /// * The en passant square (which is SQ_NONE if no en passant capture is
98 /// * The squares of the kings for both sides.
99 /// * The last move played.
100 /// * Hash keys for the position itself, the current pawn structure, and
101 /// the current material situation.
102 /// * Hash keys for all previous positions in the game (for detecting
103 /// repetition draws.
104 /// * A counter for detecting 50 move rule draws.
108 friend class MaterialInfo;
113 Position(const Position &pos);
114 Position(const std::string &fen);
117 void from_fen(const std::string &fen);
118 const std::string to_fen() const;
122 void copy(const Position &pos);
123 void flipped_copy(const Position &pos);
125 // The piece on a given square
126 Piece piece_on(Square s) const;
127 PieceType type_of_piece_on(Square s) const;
128 Color color_of_piece_on(Square s) const;
129 bool square_is_empty(Square s) const;
130 bool square_is_occupied(Square s) const;
131 Value midgame_value_of_piece_on(Square s) const;
132 Value endgame_value_of_piece_on(Square s) const;
135 Color side_to_move() const;
137 // Bitboard representation of the position
138 Bitboard empty_squares() const;
139 Bitboard occupied_squares() const;
140 Bitboard pieces_of_color(Color c) const;
141 Bitboard pieces_of_type(PieceType pt) const;
142 Bitboard pieces_of_color_and_type(Color c, PieceType pt) const;
143 Bitboard pawns() const;
144 Bitboard knights() const;
145 Bitboard bishops() const;
146 Bitboard rooks() const;
147 Bitboard queens() const;
148 Bitboard kings() const;
149 Bitboard rooks_and_queens() const;
150 Bitboard bishops_and_queens() const;
151 Bitboard sliders() const;
152 Bitboard pawns(Color c) const;
153 Bitboard knights(Color c) const;
154 Bitboard bishops(Color c) const;
155 Bitboard rooks(Color c) const;
156 Bitboard queens(Color c) const;
157 Bitboard kings(Color c) const;
158 Bitboard rooks_and_queens(Color c) const;
159 Bitboard bishops_and_queens(Color c) const;
160 Bitboard sliders_of_color(Color c) const;
162 // Number of pieces of each color and type
163 int piece_count(Color c, PieceType pt) const;
164 int pawn_count(Color c) const;
165 int knight_count(Color c) const;
166 int bishop_count(Color c) const;
167 int rook_count(Color c) const;
168 int queen_count(Color c) const;
170 // The en passant square:
171 Square ep_square() const;
173 // Current king position for each color
174 Square king_square(Color c) const;
177 bool can_castle_kingside(Color c) const;
178 bool can_castle_queenside(Color c) const;
179 bool can_castle(Color c) const;
180 Square initial_kr_square(Color c) const;
181 Square initial_qr_square(Color c) const;
184 Bitboard sliding_attacks(Square s, Direction d) const;
185 Bitboard ray_attacks(Square s, SignedDirection d) const;
186 Bitboard pawn_attacks(Color c, Square s) const;
187 Bitboard white_pawn_attacks(Square s) const;
188 Bitboard black_pawn_attacks(Square s) const;
189 Bitboard knight_attacks(Square s) const;
190 Bitboard bishop_attacks(Square s) const;
191 Bitboard rook_attacks(Square s) const;
192 Bitboard queen_attacks(Square s) const;
193 Bitboard king_attacks(Square s) const;
195 // Bitboards for pinned pieces and discovered check candidates
196 Bitboard discovered_check_candidates(Color c) const;
197 Bitboard pinned_pieces(Color c) const;
200 Bitboard checkers() const;
203 Square piece_list(Color c, PieceType pt, int index) const;
204 Square pawn_list(Color c, int index) const;
205 Square knight_list(Color c, int index) const;
206 Square bishop_list(Color c, int index) const;
207 Square rook_list(Color c, int index) const;
208 Square queen_list(Color c, int index) const;
210 // Attack information for a given square
211 bool square_is_attacked(Square s, Color c) const;
212 Bitboard attacks_to(Square s) const;
213 Bitboard attacks_to(Square s, Color c) const;
214 bool is_check() const;
215 bool piece_attacks_square(Square f, Square t) const;
216 bool white_pawn_attacks_square(Square f, Square t) const;
217 bool black_pawn_attacks_square(Square f, Square t) const;
218 bool knight_attacks_square(Square f, Square t) const;
219 bool bishop_attacks_square(Square f, Square t) const;
220 bool rook_attacks_square(Square f, Square t) const;
221 bool queen_attacks_square(Square f, Square t) const;
222 bool king_attacks_square(Square f, Square t) const;
224 // Properties of moves
225 bool move_is_legal(Move m) const;
226 bool move_is_legal(Move m, Bitboard pinned) const;
227 bool move_is_check(Move m) const;
228 bool move_is_check(Move m, Bitboard dcCandidates) const;
229 bool move_is_capture(Move m) const;
230 bool move_is_pawn_push_to_7th(Move m) const;
231 bool move_is_passed_pawn_push(Move m) const;
232 bool move_was_passed_pawn_push(Move m) const;
233 bool move_attacks_square(Move m, Square s) const;
235 // Information about pawns
236 bool pawn_is_passed(Color c, Square s) const;
237 bool pawn_is_isolated(Color c, Square s) const;
238 bool pawn_is_doubled(Color c, Square s) const;
240 // Open and half-open files
241 bool file_is_open(File f) const;
242 bool file_is_half_open(Color c, File f) const;
245 bool square_is_weak(Square s, Color c) const;
247 // Doing and undoing moves
248 void backup(UndoInfo &u) const;
249 void restore(const UndoInfo &u);
250 void do_move(Move m, UndoInfo &u);
251 void do_move(Move m, UndoInfo &u, Bitboard dcCandidates);
252 void undo_move(Move m, const UndoInfo &u);
253 void do_null_move(UndoInfo &u);
254 void undo_null_move(const UndoInfo &u);
256 // Static exchange evaluation
257 int see(Square from, Square to) const;
258 int see(Move m) const;
260 // Accessing hash keys
262 Key get_pawn_key() const;
263 Key get_material_key() const;
265 // Incremental evaluation
266 Value mg_value() const;
267 Value eg_value() const;
268 Value non_pawn_material(Color c) const;
269 Phase game_phase() const;
271 // Game termination checks
273 bool is_draw() const;
275 // Check if one side threatens a mate in one
276 bool has_mate_threat(Color c);
278 // Number of plies since the last non-reversible move
279 int rule_50_counter() const;
281 // Other properties of the position
282 bool opposite_colored_bishops() const;
283 bool has_pawn_on_7th(Color c) const;
285 // Reset the gamePly variable to 0
286 void reset_game_ply();
288 // Position consistency check, for debugging
291 // Static member functions:
292 static void init_zobrist();
293 static void init_piece_square_tables();
296 // Initialization helper functions (used while setting up a position)
298 void put_piece(Piece p, Square s);
299 void allow_oo(Color c);
300 void allow_ooo(Color c);
302 // Helper functions for doing and undoing moves
303 void do_castle_move(Move m);
304 void do_promotion_move(Move m, UndoInfo &u);
305 void do_ep_move(Move m);
306 void undo_castle_move(Move m);
307 void undo_promotion_move(Move m, const UndoInfo &u);
308 void undo_ep_move(Move m);
309 void find_checkers();
311 // Computing hash keys from scratch (for initialization and debugging)
312 Key compute_key() const;
313 Key compute_pawn_key() const;
314 Key compute_material_key() const;
316 // Computing incremental evaluation scores and material counts
317 Value mg_pst(Color c, PieceType pt, Square s) const;
318 Value eg_pst(Color c, PieceType pt, Square s) const;
319 Value compute_mg_value() const;
320 Value compute_eg_value() const;
321 Value compute_non_pawn_material(Color c) const;
324 Bitboard byColorBB[2], byTypeBB[8];
331 int pieceCount[2][8]; // [color][pieceType]
334 Square pieceList[2][8][16]; // [color][pieceType][index]
340 File initialKFile, initialKRFile, initialQRFile;
342 Square kingSquare[2];
344 Key key, pawnKey, materialKey, history[MaxGameLength];
346 Value mgValue, egValue;
350 static int castleRightsMask[64];
351 static Key zobrist[2][8][64];
352 static Key zobEp[64];
353 static Key zobCastle[16];
354 static Key zobMaterial[2][8][16];
355 static Key zobSideToMove;
356 static Value MgPieceSquareTable[16][64];
357 static Value EgPieceSquareTable[16][64];
362 //// Inline functions
365 inline Piece Position::piece_on(Square s) const {
369 inline Color Position::color_of_piece_on(Square s) const {
370 return color_of_piece(this->piece_on(s));
373 inline PieceType Position::type_of_piece_on(Square s) const {
374 return type_of_piece(this->piece_on(s));
377 inline bool Position::square_is_empty(Square s) const {
378 return this->piece_on(s) == EMPTY;
381 inline bool Position::square_is_occupied(Square s) const {
382 return !this->square_is_empty(s);
385 inline Value Position::midgame_value_of_piece_on(Square s) const {
386 return piece_value_midgame(this->piece_on(s));
389 inline Value Position::endgame_value_of_piece_on(Square s) const {
390 return piece_value_endgame(this->piece_on(s));
393 inline Color Position::side_to_move() const {
397 inline Bitboard Position::occupied_squares() const {
401 inline Bitboard Position::empty_squares() const {
402 return ~(this->occupied_squares());
405 inline Bitboard Position::pieces_of_color(Color c) const {
409 inline Bitboard Position::pieces_of_type(PieceType pt) const {
413 inline Bitboard Position::pieces_of_color_and_type(Color c, PieceType pt)
415 return this->pieces_of_color(c) & this->pieces_of_type(pt);
418 inline Bitboard Position::pawns() const {
419 return this->pieces_of_type(PAWN);
422 inline Bitboard Position::knights() const {
423 return this->pieces_of_type(KNIGHT);
426 inline Bitboard Position::bishops() const {
427 return this->pieces_of_type(BISHOP);
430 inline Bitboard Position::rooks() const {
431 return this->pieces_of_type(ROOK);
434 inline Bitboard Position::queens() const {
435 return this->pieces_of_type(QUEEN);
438 inline Bitboard Position::kings() const {
439 return this->pieces_of_type(KING);
442 inline Bitboard Position::rooks_and_queens() const {
443 return this->rooks() | this->queens();
446 inline Bitboard Position::bishops_and_queens() const {
447 return this->bishops() | this->queens();
450 inline Bitboard Position::sliders() const {
451 return this->bishops() | this->queens() | this->rooks();
454 inline Bitboard Position::pawns(Color c) const {
455 return this->pieces_of_color_and_type(c, PAWN);
458 inline Bitboard Position::knights(Color c) const {
459 return this->pieces_of_color_and_type(c, KNIGHT);
462 inline Bitboard Position::bishops(Color c) const {
463 return this->pieces_of_color_and_type(c, BISHOP);
466 inline Bitboard Position::rooks(Color c) const {
467 return this->pieces_of_color_and_type(c, ROOK);
470 inline Bitboard Position::queens(Color c) const {
471 return this->pieces_of_color_and_type(c, QUEEN);
474 inline Bitboard Position::kings(Color c) const {
475 return this->pieces_of_color_and_type(c, KING);
478 inline Bitboard Position::rooks_and_queens(Color c) const {
479 return this->rooks_and_queens() & this->pieces_of_color(c);
482 inline Bitboard Position::bishops_and_queens(Color c) const {
483 return this->bishops_and_queens() & this->pieces_of_color(c);
486 inline Bitboard Position::sliders_of_color(Color c) const {
487 return this->sliders() & this->pieces_of_color(c);
490 inline int Position::piece_count(Color c, PieceType pt) const {
491 return pieceCount[c][pt];
494 inline int Position::pawn_count(Color c) const {
495 return this->piece_count(c, PAWN);
498 inline int Position::knight_count(Color c) const {
499 return this->piece_count(c, KNIGHT);
502 inline int Position::bishop_count(Color c) const {
503 return this->piece_count(c, BISHOP);
506 inline int Position::rook_count(Color c) const {
507 return this->piece_count(c, ROOK);
510 inline int Position::queen_count(Color c) const {
511 return this->piece_count(c, QUEEN);
514 inline Square Position::piece_list(Color c, PieceType pt, int index) const {
515 return pieceList[c][pt][index];
518 inline Square Position::pawn_list(Color c, int index) const {
519 return this->piece_list(c, PAWN, index);
522 inline Square Position::knight_list(Color c, int index) const {
523 return this->piece_list(c, KNIGHT, index);
526 inline Square Position::bishop_list(Color c, int index) const {
527 return this->piece_list(c, BISHOP, index);
530 inline Square Position::rook_list(Color c, int index) const {
531 return this->piece_list(c, ROOK, index);
534 inline Square Position::queen_list(Color c, int index) const {
535 return this->piece_list(c, QUEEN, index);
538 inline Square Position::ep_square() const {
542 inline Square Position::king_square(Color c) const {
543 return kingSquare[c];
546 inline bool Position::can_castle_kingside(Color side) const {
547 return castleRights & (1+int(side));
550 inline bool Position::can_castle_queenside(Color side) const {
551 return castleRights & (4+4*int(side));
554 inline bool Position::can_castle(Color side) const {
555 return can_castle_kingside(side) || can_castle_queenside(side);
558 inline Square Position::initial_kr_square(Color c) const {
559 return relative_square(c, make_square(initialKRFile, RANK_1));
562 inline Square Position::initial_qr_square(Color c) const {
563 return relative_square(c, make_square(initialQRFile, RANK_1));
566 inline Bitboard Position::pawn_attacks(Color c, Square s) const {
567 return StepAttackBB[pawn_of_color(c)][s];
570 inline Bitboard Position::white_pawn_attacks(Square s) const {
571 return this->pawn_attacks(WHITE, s);
574 inline Bitboard Position::black_pawn_attacks(Square s) const {
575 return this->pawn_attacks(BLACK, s);
578 inline Bitboard Position::knight_attacks(Square s) const {
579 return StepAttackBB[KNIGHT][s];
582 inline Bitboard Position::rook_attacks(Square s) const {
583 return rook_attacks_bb(s, this->occupied_squares());
586 inline Bitboard Position::bishop_attacks(Square s) const {
587 return bishop_attacks_bb(s, this->occupied_squares());
590 inline Bitboard Position::queen_attacks(Square s) const {
591 return this->rook_attacks(s) | this->bishop_attacks(s);
594 inline Bitboard Position::king_attacks(Square s) const {
595 return StepAttackBB[KING][s];
598 inline Bitboard Position::checkers() const {
602 inline bool Position::is_check() const {
603 return this->checkers() != EmptyBoardBB;
606 inline bool Position::white_pawn_attacks_square(Square f, Square t) const {
607 return bit_is_set(this->white_pawn_attacks(f), t);
610 inline bool Position::black_pawn_attacks_square(Square f, Square t) const {
611 return bit_is_set(this->black_pawn_attacks(f), t);
614 inline bool Position::knight_attacks_square(Square f, Square t) const {
615 return bit_is_set(this->knight_attacks(f), t);
618 inline bool Position::bishop_attacks_square(Square f, Square t) const {
619 return bit_is_set(this->bishop_attacks(f), t);
622 inline bool Position::rook_attacks_square(Square f, Square t) const {
623 return bit_is_set(this->rook_attacks(f), t);
626 inline bool Position::queen_attacks_square(Square f, Square t) const {
627 return bit_is_set(this->queen_attacks(f), t);
630 inline bool Position::king_attacks_square(Square f, Square t) const {
631 return bit_is_set(this->king_attacks(f), t);
634 inline bool Position::pawn_is_passed(Color c, Square s) const {
635 return !(this->pawns(opposite_color(c)) & passed_pawn_mask(c, s));
638 inline bool Position::pawn_is_isolated(Color c, Square s) const {
639 return !(this->pawns(c) & neighboring_files_bb(s));
642 inline bool Position::pawn_is_doubled(Color c, Square s) const {
643 return this->pawns(c) & squares_behind(c, s);
646 inline bool Position::file_is_open(File f) const {
647 return !(this->pawns() & file_bb(f));
650 inline bool Position::file_is_half_open(Color c, File f) const {
651 return !(this->pawns(c) & file_bb(f));
654 inline bool Position::square_is_weak(Square s, Color c) const {
655 return !(this->pawns(c) & outpost_mask(opposite_color(c), s));
658 inline Key Position::get_key() const {
662 inline Key Position::get_pawn_key() const {
666 inline Key Position::get_material_key() const {
670 inline Value Position::mg_pst(Color c, PieceType pt, Square s) const {
671 return MgPieceSquareTable[piece_of_color_and_type(c, pt)][s];
674 inline Value Position::eg_pst(Color c, PieceType pt, Square s) const {
675 return EgPieceSquareTable[piece_of_color_and_type(c, pt)][s];
678 inline Value Position::mg_value() const {
682 inline Value Position::eg_value() const {
686 inline Value Position::non_pawn_material(Color c) const {
687 return npMaterial[c];
690 inline Phase Position::game_phase() const {
692 // The purpose of the Value(325) terms below is to make sure the difference
693 // between MidgameLimit and EndgameLimit is a power of 2, which should make
694 // the division at the end of the function a bit faster.
696 static const Value MidgameLimit =
697 2*QueenValueMidgame+2*RookValueMidgame+6*BishopValueMidgame+Value(325);
698 static const Value EndgameLimit = 4*RookValueMidgame-Value(325);
699 Value npm = this->non_pawn_material(WHITE) + this->non_pawn_material(BLACK);
701 if(npm >= MidgameLimit)
702 return PHASE_MIDGAME;
703 else if(npm <= EndgameLimit)
704 return PHASE_ENDGAME;
706 return Phase(((npm - EndgameLimit) * 128) / (MidgameLimit - EndgameLimit));
709 inline bool Position::move_is_pawn_push_to_7th(Move m) const {
710 Color c = this->side_to_move();
712 this->piece_on(move_from(m)) == pawn_of_color(c) &&
713 pawn_rank(c, move_to(m)) == RANK_7;
716 inline bool Position::move_is_passed_pawn_push(Move m) const {
717 Color c = this->side_to_move();
719 this->piece_on(move_from(m)) == pawn_of_color(c) &&
720 this->pawn_is_passed(c, move_to(m));
723 inline bool Position::move_was_passed_pawn_push(Move m) const {
724 Color c = opposite_color(this->side_to_move());
726 this->piece_on(move_to(m)) == pawn_of_color(c) &&
727 this->pawn_is_passed(c, move_to(m));
730 inline int Position::rule_50_counter() const {
734 inline bool Position::opposite_colored_bishops() const {
736 this->bishop_count(WHITE) == 1 && this->bishop_count(BLACK) == 1 &&
737 square_color(this->bishop_list(WHITE, 0)) !=
738 square_color(this->bishop_list(BLACK, 0));
741 inline bool Position::has_pawn_on_7th(Color c) const {
742 return this->pawns(c) & relative_rank_bb(c, RANK_7);
746 #endif // !defined(POSITION_H_INCLUDED)