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  1. /*
  2.   Stockfish, a UCI chess playing engine derived from Glaurung 2.1
  3.   Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
  4.   Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
  5.   Copyright (C) 2015-2016 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
  6.  
  7.   Stockfish is free software: you can redistribute it and/or modify
  8.   it under the terms of the GNU General Public License as published by
  9.   the Free Software Foundation, either version 3 of the License, or
  10.   (at your option) any later version.
  11.  
  12.   Stockfish is distributed in the hope that it will be useful,
  13.   but WITHOUT ANY WARRANTY; without even the implied warranty of
  14.   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15.   GNU General Public License for more details.
  16.  
  17.   You should have received a copy of the GNU General Public License
  18.   along with this program.  If not, see <http://www.gnu.org/licenses/>.
  19. */
  20.  
  21. #ifndef POSITION_H_INCLUDED
  22. #define POSITION_H_INCLUDED
  23.  
  24. #include <cassert>
  25. #include <deque>
  26. #include <memory> // For std::unique_ptr
  27. #include <string>
  28.  
  29. #include "bitboard.h"
  30. #include "types.h"
  31.  
  32.  
  33. /// StateInfo struct stores information needed to restore a Position object to
  34. /// its previous state when we retract a move. Whenever a move is made on the
  35. /// board (by calling Position::do_move), a StateInfo object must be passed.
  36.  
  37. struct StateInfo {
  38.  
  39.   // Copied when making a move
  40.   Key    pawnKey;
  41.   Key    materialKey;
  42.   Value  nonPawnMaterial[COLOR_NB];
  43.   int    castlingRights;
  44.   int    rule50;
  45.   int    pliesFromNull;
  46.   Score  psq;
  47.   Square epSquare;
  48.  
  49.   // Not copied when making a move (will be recomputed anyhow)
  50.   Key        key;
  51.   Bitboard   checkersBB;
  52.   Piece      capturedPiece;
  53.   StateInfo* previous;
  54.   Bitboard   blockersForKing[COLOR_NB];
  55.   Bitboard   pinnersForKing[COLOR_NB];
  56.   Bitboard   checkSquares[PIECE_TYPE_NB];
  57. };
  58.  
  59. // In a std::deque references to elements are unaffected upon resizing
  60. typedef std::unique_ptr<std::deque<StateInfo>> StateListPtr;
  61.  
  62.  
  63. /// Position class stores information regarding the board representation as
  64. /// pieces, side to move, hash keys, castling info, etc. Important methods are
  65. /// do_move() and undo_move(), used by the search to update node info when
  66. /// traversing the search tree.
  67. class Thread;
  68.  
  69. class Position {
  70. public:
  71.   static void init();
  72.  
  73.   Position() = default;
  74.   Position(const Position&) = delete;
  75.   Position& operator=(const Position&) = delete;
  76.  
  77.   // FEN string input/output
  78.   Position& set(const std::string& fenStr, bool isChess960, StateInfo* si, Thread* th);
  79.   const std::string fen() const;
  80.  
  81.   // Position representation
  82.   Bitboard pieces() const;
  83.   Bitboard pieces(PieceType pt) const;
  84.   Bitboard pieces(PieceType pt1, PieceType pt2) const;
  85.   Bitboard pieces(Color c) const;
  86.   Bitboard pieces(Color c, PieceType pt) const;
  87.   Bitboard pieces(Color c, PieceType pt1, PieceType pt2) const;
  88.   Piece piece_on(Square s) const;
  89.   Square ep_square() const;
  90.   bool empty(Square s) const;
  91.   template<PieceType Pt> int count(Color c) const;
  92.   template<PieceType Pt> const Square* squares(Color c) const;
  93.   template<PieceType Pt> Square square(Color c) const;
  94.  
  95.   // Castling
  96.   int can_castle(Color c) const;
  97.   int can_castle(CastlingRight cr) const;
  98.   bool castling_impeded(CastlingRight cr) const;
  99.   Square castling_rook_square(CastlingRight cr) const;
  100.  
  101.   // Checking
  102.   Bitboard checkers() const;
  103.   Bitboard discovered_check_candidates() const;
  104.   Bitboard pinned_pieces(Color c) const;
  105.   Bitboard check_squares(PieceType pt) const;
  106.  
  107.   // Attacks to/from a given square
  108.   Bitboard attackers_to(Square s) const;
  109.   Bitboard attackers_to(Square s, Bitboard occupied) const;
  110.   Bitboard attacks_from(Piece pc, Square s) const;
  111.   template<PieceType> Bitboard attacks_from(Square s) const;
  112.   template<PieceType> Bitboard attacks_from(Square s, Color c) const;
  113.   Bitboard slider_blockers(Bitboard sliders, Square s, Bitboard& pinners) const;
  114.  
  115.   // Properties of moves
  116.   bool legal(Move m) const;
  117.   bool pseudo_legal(const Move m) const;
  118.   bool capture(Move m) const;
  119.   bool capture_or_promotion(Move m) const;
  120.   bool gives_check(Move m) const;
  121.   bool advanced_pawn_push(Move m) const;
  122.   Piece moved_piece(Move m) const;
  123.   Piece captured_piece() const;
  124.  
  125.   // Piece specific
  126.   bool pawn_passed(Color c, Square s) const;
  127.   bool opposite_bishops() const;
  128.  
  129.   // Doing and undoing moves
  130.   void do_move(Move m, StateInfo& st, bool givesCheck);
  131.   void undo_move(Move m);
  132.   void do_null_move(StateInfo& st);
  133.   void undo_null_move();
  134.  
  135.   // Static Exchange Evaluation
  136.   bool see_ge(Move m, Value value) const;
  137.  
  138.   // Accessing hash keys
  139.   Key key() const;
  140.   Key key_after(Move m) const;
  141.   Key material_key() const;
  142.   Key pawn_key() const;
  143.  
  144.   // Other properties of the position
  145.   Color side_to_move() const;
  146.   Phase game_phase() const;
  147.   int game_ply() const;
  148.   bool is_chess960() const;
  149.   Thread* this_thread() const;
  150.   uint64_t nodes_searched() const;
  151.   bool is_draw() const;
  152.   int rule50_count() const;
  153.   Score psq_score() const;
  154.   Value non_pawn_material(Color c) const;
  155.  
  156.   // Position consistency check, for debugging
  157.   bool pos_is_ok(int* failedStep = nullptr) const;
  158.   void flip();
  159.  
  160. private:
  161.   // Initialization helpers (used while setting up a position)
  162.   void set_castling_right(Color c, Square rfrom);
  163.   void set_state(StateInfo* si) const;
  164.   void set_check_info(StateInfo* si) const;
  165.  
  166.   // Other helpers
  167.   void put_piece(Piece pc, Square s);
  168.   void remove_piece(Piece pc, Square s);
  169.   void move_piece(Piece pc, Square from, Square to);
  170.   template<bool Do>
  171.   void do_castling(Color us, Square from, Square& to, Square& rfrom, Square& rto);
  172.  
  173.   // Data members
  174.   Piece board[SQUARE_NB];
  175.   Bitboard byTypeBB[PIECE_TYPE_NB];
  176.   Bitboard byColorBB[COLOR_NB];
  177.   int pieceCount[PIECE_NB];
  178.   Square pieceList[PIECE_NB][16];
  179.   int index[SQUARE_NB];
  180.   int castlingRightsMask[SQUARE_NB];
  181.   Square castlingRookSquare[CASTLING_RIGHT_NB];
  182.   Bitboard castlingPath[CASTLING_RIGHT_NB];
  183.   uint64_t nodes;
  184.   int gamePly;
  185.   Color sideToMove;
  186.   Thread* thisThread;
  187.   StateInfo* st;
  188.   bool chess960;
  189. };
  190.  
  191. extern std::ostream& operator<<(std::ostream& os, const Position& pos);
  192.  
  193. inline Color Position::side_to_move() const {
  194.   return sideToMove;
  195. }
  196.  
  197. inline bool Position::empty(Square s) const {
  198.   return board[s] == NO_PIECE;
  199. }
  200.  
  201. inline Piece Position::piece_on(Square s) const {
  202.   return board[s];
  203. }
  204.  
  205. inline Piece Position::moved_piece(Move m) const {
  206.   return board[from_sq(m)];
  207. }
  208.  
  209. inline Bitboard Position::pieces() const {
  210.   return byTypeBB[ALL_PIECES];
  211. }
  212.  
  213. inline Bitboard Position::pieces(PieceType pt) const {
  214.   return byTypeBB[pt];
  215. }
  216.  
  217. inline Bitboard Position::pieces(PieceType pt1, PieceType pt2) const {
  218.   return byTypeBB[pt1] | byTypeBB[pt2];
  219. }
  220.  
  221. inline Bitboard Position::pieces(Color c) const {
  222.   return byColorBB[c];
  223. }
  224.  
  225. inline Bitboard Position::pieces(Color c, PieceType pt) const {
  226.   return byColorBB[c] & byTypeBB[pt];
  227. }
  228.  
  229. inline Bitboard Position::pieces(Color c, PieceType pt1, PieceType pt2) const {
  230.   return byColorBB[c] & (byTypeBB[pt1] | byTypeBB[pt2]);
  231. }
  232.  
  233. template<PieceType Pt> inline int Position::count(Color c) const {
  234.   return pieceCount[make_piece(c, Pt)];
  235. }
  236.  
  237. template<PieceType Pt> inline const Square* Position::squares(Color c) const {
  238.   return pieceList[make_piece(c, Pt)];
  239. }
  240.  
  241. template<PieceType Pt> inline Square Position::square(Color c) const {
  242.   assert(pieceCount[make_piece(c, Pt)] == 1);
  243.   return pieceList[make_piece(c, Pt)][0];
  244. }
  245.  
  246. inline Square Position::ep_square() const {
  247.   return st->epSquare;
  248. }
  249.  
  250. inline int Position::can_castle(CastlingRight cr) const {
  251.   return st->castlingRights & cr;
  252. }
  253.  
  254. inline int Position::can_castle(Color c) const {
  255.   return st->castlingRights & ((WHITE_OO | WHITE_OOO) << (2 * c));
  256. }
  257.  
  258. inline bool Position::castling_impeded(CastlingRight cr) const {
  259.   return byTypeBB[ALL_PIECES] & castlingPath[cr];
  260. }
  261.  
  262. inline Square Position::castling_rook_square(CastlingRight cr) const {
  263.   return castlingRookSquare[cr];
  264. }
  265.  
  266. template<PieceType Pt>
  267. inline Bitboard Position::attacks_from(Square s) const {
  268.   return  Pt == BISHOP || Pt == ROOK ? attacks_bb<Pt>(s, byTypeBB[ALL_PIECES])
  269.         : Pt == QUEEN  ? attacks_from<ROOK>(s) | attacks_from<BISHOP>(s)
  270.         : StepAttacksBB[Pt][s];
  271. }
  272.  
  273. template<>
  274. inline Bitboard Position::attacks_from<PAWN>(Square s, Color c) const {
  275.   return StepAttacksBB[make_piece(c, PAWN)][s];
  276. }
  277.  
  278. inline Bitboard Position::attacks_from(Piece pc, Square s) const {
  279.   return attacks_bb(pc, s, byTypeBB[ALL_PIECES]);
  280. }
  281.  
  282. inline Bitboard Position::attackers_to(Square s) const {
  283.   return attackers_to(s, byTypeBB[ALL_PIECES]);
  284. }
  285.  
  286. inline Bitboard Position::checkers() const {
  287.   return st->checkersBB;
  288. }
  289.  
  290. inline Bitboard Position::discovered_check_candidates() const {
  291.   return st->blockersForKing[~sideToMove] & pieces(sideToMove);
  292. }
  293.  
  294. inline Bitboard Position::pinned_pieces(Color c) const {
  295.   return st->blockersForKing[c] & pieces(c);
  296. }
  297.  
  298. inline Bitboard Position::check_squares(PieceType pt) const {
  299.   return st->checkSquares[pt];
  300. }
  301.  
  302. inline bool Position::pawn_passed(Color c, Square s) const {
  303.   return !(pieces(~c, PAWN) & passed_pawn_mask(c, s));
  304. }
  305.  
  306. inline bool Position::advanced_pawn_push(Move m) const {
  307.   return   type_of(moved_piece(m)) == PAWN
  308.         && relative_rank(sideToMove, from_sq(m)) > RANK_4;
  309. }
  310.  
  311. inline Key Position::key() const {
  312.   return st->key;
  313. }
  314.  
  315. inline Key Position::pawn_key() const {
  316.   return st->pawnKey;
  317. }
  318.  
  319. inline Key Position::material_key() const {
  320.   return st->materialKey;
  321. }
  322.  
  323. inline Score Position::psq_score() const {
  324.   return st->psq;
  325. }
  326.  
  327. inline Value Position::non_pawn_material(Color c) const {
  328.   return st->nonPawnMaterial[c];
  329. }
  330.  
  331. inline int Position::game_ply() const {
  332.   return gamePly;
  333. }
  334.  
  335. inline int Position::rule50_count() const {
  336.   return st->rule50;
  337. }
  338.  
  339. inline uint64_t Position::nodes_searched() const {
  340.   return nodes;
  341. }
  342.  
  343. inline bool Position::opposite_bishops() const {
  344.   return   pieceCount[W_BISHOP] == 1
  345.         && pieceCount[B_BISHOP] == 1
  346.         && opposite_colors(square<BISHOP>(WHITE), square<BISHOP>(BLACK));
  347. }
  348.  
  349. inline bool Position::is_chess960() const {
  350.   return chess960;
  351. }
  352.  
  353. inline bool Position::capture_or_promotion(Move m) const {
  354.   assert(is_ok(m));
  355.   return type_of(m) != NORMAL ? type_of(m) != CASTLING : !empty(to_sq(m));
  356. }
  357.  
  358. inline bool Position::capture(Move m) const {
  359.   assert(is_ok(m));
  360.   // Castling is encoded as "king captures rook"
  361.   return (!empty(to_sq(m)) && type_of(m) != CASTLING) || type_of(m) == ENPASSANT;
  362. }
  363.  
  364. inline Piece Position::captured_piece() const {
  365.   return st->capturedPiece;
  366. }
  367.  
  368. inline Thread* Position::this_thread() const {
  369.   return thisThread;
  370. }
  371.  
  372. inline void Position::put_piece(Piece pc, Square s) {
  373.  
  374.   board[s] = pc;
  375.   byTypeBB[ALL_PIECES] |= s;
  376.   byTypeBB[type_of(pc)] |= s;
  377.   byColorBB[color_of(pc)] |= s;
  378.   index[s] = pieceCount[pc]++;
  379.   pieceList[pc][index[s]] = s;
  380.   pieceCount[make_piece(color_of(pc), ALL_PIECES)]++;
  381. }
  382.  
  383. inline void Position::remove_piece(Piece pc, Square s) {
  384.  
  385.   // WARNING: This is not a reversible operation. If we remove a piece in
  386.   // do_move() and then replace it in undo_move() we will put it at the end of
  387.   // the list and not in its original place, it means index[] and pieceList[]
  388.   // are not invariant to a do_move() + undo_move() sequence.
  389.   byTypeBB[ALL_PIECES] ^= s;
  390.   byTypeBB[type_of(pc)] ^= s;
  391.   byColorBB[color_of(pc)] ^= s;
  392.   /* board[s] = NO_PIECE;  Not needed, overwritten by the capturing one */
  393.   Square lastSquare = pieceList[pc][--pieceCount[pc]];
  394.   index[lastSquare] = index[s];
  395.   pieceList[pc][index[lastSquare]] = lastSquare;
  396.   pieceList[pc][pieceCount[pc]] = SQ_NONE;
  397.   pieceCount[make_piece(color_of(pc), ALL_PIECES)]--;
  398. }
  399.  
  400. inline void Position::move_piece(Piece pc, Square from, Square to) {
  401.  
  402.   // index[from] is not updated and becomes stale. This works as long as index[]
  403.   // is accessed just by known occupied squares.
  404.   Bitboard from_to_bb = SquareBB[from] ^ SquareBB[to];
  405.   byTypeBB[ALL_PIECES] ^= from_to_bb;
  406.   byTypeBB[type_of(pc)] ^= from_to_bb;
  407.   byColorBB[color_of(pc)] ^= from_to_bb;
  408.   board[from] = NO_PIECE;
  409.   board[to] = pc;
  410.   index[to] = index[from];
  411.   pieceList[pc][index[to]] = to;
  412. }
  413.  
  414. #endif // #ifndef POSITION_H_INCLUDED
  415.