};
-/// The StateInfo struct stores information we need to restore a Position
+/// The StateInfo struct stores information needed to restore a Position
/// object to its previous state when we retract a move. Whenever a move
-/// is made on the board (by calling Position::do_move), a StateInfo object
-/// must be passed as a parameter.
+/// is made on the board (by calling Position::do_move), a StateInfo
+/// object must be passed as a parameter.
struct StateInfo {
Key pawnKey, materialKey;
const size_t StateCopySize64 = offsetof(StateInfo, key) / sizeof(uint64_t) + 1;
-/// The position data structure. A position consists of the following data:
-///
-/// * For each piece type, a bitboard representing the squares occupied
-/// by pieces of that type.
-/// * For each color, a bitboard representing the squares occupied by
-/// pieces of that color.
-/// * A bitboard of all occupied squares.
-/// * A bitboard of all checking pieces.
-/// * A 64-entry array of pieces, indexed by the squares of the board.
-/// * The current side to move.
-/// * Information about the castling rights for both sides.
-/// * The initial files of the kings and both pairs of rooks. This is
-/// used to implement the Chess960 castling rules.
-/// * The en passant square (which is SQ_NONE if no en passant capture is
-/// possible).
-/// * The squares of the kings for both sides.
-/// * Hash keys for the position itself, the current pawn structure, and
-/// the current material situation.
-/// * Hash keys for all previous positions in the game for detecting
-/// repetition draws.
-/// * A counter for detecting 50 move rule draws.
+/// The Position class stores the information regarding the board representation
+/// like pieces, side to move, hash keys, castling info, etc. The most important
+/// methods are do_move() and undo_move(), used by the search to update node info
+/// when traversing the search tree.
class Position {
public:
Piece piece_on(Square s) const;
Square king_square(Color c) const;
Square ep_square() const;
- bool is_empty(Square s) const;
+ bool empty(Square s) const;
template<PieceType Pt> int count(Color c) const;
template<PieceType Pt> const Square* list(Color c) const;
// Checking
Bitboard checkers() const;
Bitboard discovered_check_candidates() const;
- Bitboard pinned_pieces() const;
+ Bitboard pinned_pieces(Color toMove) const;
// Attacks to/from a given square
Bitboard attackers_to(Square s) const;
Bitboard attackers_to(Square s, Bitboard occ) const;
Bitboard attacks_from(Piece p, Square s) const;
- static Bitboard attacks_from(Piece p, Square s, Bitboard occ);
template<PieceType> Bitboard attacks_from(Square s) const;
template<PieceType> Bitboard attacks_from(Square s, Color c) const;
// Properties of moves
- bool move_gives_check(Move m, const CheckInfo& ci) const;
- bool pl_move_is_legal(Move m, Bitboard pinned) const;
- bool is_pseudo_legal(const Move m) const;
- bool is_capture(Move m) const;
- bool is_capture_or_promotion(Move m) const;
- bool is_passed_pawn_push(Move m) const;
- Piece piece_moved(Move m) const;
+ bool legal(Move m, Bitboard pinned) const;
+ bool pseudo_legal(const Move m) const;
+ bool capture(Move m) const;
+ bool capture_or_promotion(Move m) const;
+ bool gives_check(Move m, const CheckInfo& ci) const;
+ bool passed_pawn_push(Move m) const;
+ Piece moved_piece(Move m) const;
PieceType captured_piece_type() const;
// Piece specific
- bool pawn_is_passed(Color c, Square s) const;
+ bool pawn_passed(Color c, Square s) const;
bool pawn_on_7th(Color c) const;
- bool opposite_bishops() const;
bool bishop_pair(Color c) const;
+ bool opposite_bishops() const;
// Doing and undoing moves
void do_move(Move m, StateInfo& st);
private:
// Initialization helpers (used while setting up a position)
void clear();
- void put_piece(Piece p, Square s);
void set_castle_right(Color c, Square rfrom);
// Helper functions
void do_castle(Square kfrom, Square kto, Square rfrom, Square rto);
- Bitboard hidden_checkers(Square ksq, Color c) const;
+ Bitboard hidden_checkers(Square ksq, Color c, Color toMove) const;
+ void put_piece(Square s, Color c, PieceType pt);
void remove_piece(Square s, Color c, PieceType pt);
- void add_piece(Square s, Color c, PieceType pt);
void move_piece(Square from, Square to, Color c, PieceType pt);
// Computing hash keys from scratch (for initialization and debugging)
return board[s];
}
-inline Piece Position::piece_moved(Move m) const {
+inline Piece Position::moved_piece(Move m) const {
return board[from_sq(m)];
}
-inline bool Position::is_empty(Square s) const {
+inline bool Position::empty(Square s) const {
return board[s] == NO_PIECE;
}
}
inline Bitboard Position::attacks_from(Piece p, Square s) const {
- return attacks_from(p, s, byTypeBB[ALL_PIECES]);
+ return attacks_bb(p, s, byTypeBB[ALL_PIECES]);
}
inline Bitboard Position::attackers_to(Square s) const {
}
inline Bitboard Position::discovered_check_candidates() const {
- return hidden_checkers(king_square(~sideToMove), sideToMove);
+ return hidden_checkers(king_square(~sideToMove), sideToMove, sideToMove);
}
-inline Bitboard Position::pinned_pieces() const {
- return hidden_checkers(king_square(sideToMove), ~sideToMove);
+inline Bitboard Position::pinned_pieces(Color toMove) const {
+ return hidden_checkers(king_square(toMove), ~toMove, toMove);
}
-inline bool Position::pawn_is_passed(Color c, Square s) const {
+inline bool Position::pawn_passed(Color c, Square s) const {
return !(pieces(~c, PAWN) & passed_pawn_mask(c, s));
}
+inline bool Position::passed_pawn_push(Move m) const {
+
+ return type_of(moved_piece(m)) == PAWN
+ && pawn_passed(sideToMove, to_sq(m));
+}
+
inline Key Position::key() const {
return st->key;
}
return st->npMaterial[c];
}
-inline bool Position::is_passed_pawn_push(Move m) const {
-
- return type_of(piece_moved(m)) == PAWN
- && pawn_is_passed(sideToMove, to_sq(m));
-}
-
inline int Position::game_ply() const {
return gamePly;
}
return chess960;
}
-inline bool Position::is_capture_or_promotion(Move m) const {
+inline bool Position::capture_or_promotion(Move m) const {
assert(is_ok(m));
- return type_of(m) ? type_of(m) != CASTLE : !is_empty(to_sq(m));
+ return type_of(m) ? type_of(m) != CASTLE : !empty(to_sq(m));
}
-inline bool Position::is_capture(Move m) const {
+inline bool Position::capture(Move m) const {
// Note that castle is coded as "king captures the rook"
assert(is_ok(m));
- return (!is_empty(to_sq(m)) && type_of(m) != CASTLE) || type_of(m) == ENPASSANT;
+ return (!empty(to_sq(m)) && type_of(m) != CASTLE) || type_of(m) == ENPASSANT;
}
inline PieceType Position::captured_piece_type() const {
return thisThread;
}
-inline void Position::add_piece(Square s, Color c, PieceType pt) {
+inline void Position::put_piece(Square s, Color c, PieceType pt) {
+
+ board[s] = make_piece(c, pt);
+ byTypeBB[ALL_PIECES] |= s;
+ byTypeBB[pt] |= s;
+ byColorBB[c] |= s;
+ pieceCount[c][ALL_PIECES]++;
index[s] = pieceCount[c][pt]++;
pieceList[c][pt][index[s]] = s;
}
inline void Position::move_piece(Square from, Square to, Color c, PieceType pt) {
+
// index[from] is not updated and becomes stale. This works as long
// as index[] is accessed just by known occupied squares.
+ Bitboard from_to_bb = SquareBB[from] ^ SquareBB[to];
+ byTypeBB[ALL_PIECES] ^= from_to_bb;
+ byTypeBB[pt] ^= from_to_bb;
+ byColorBB[c] ^= from_to_bb;
+ board[from] = NO_PIECE;
+ board[to] = make_piece(c, pt);
index[to] = index[from];
pieceList[c][pt][index[to]] = to;
}
inline void Position::remove_piece(Square s, Color c, PieceType pt) {
+
// WARNING: This is not a reversible operation. If we remove a piece in
// do_move() and then replace it in undo_move() we will put it at the end of
// the list and not in its original place, it means index[] and pieceList[]
// are not guaranteed to be invariant to a do_move() + undo_move() sequence.
+ byTypeBB[ALL_PIECES] ^= s;
+ byTypeBB[pt] ^= s;
+ byColorBB[c] ^= s;
+ /* board[s] = NO_PIECE; */ // Not needed, will be overwritten by capturing
+ pieceCount[c][ALL_PIECES]--;
Square lastSquare = pieceList[c][pt][--pieceCount[c][pt]];
index[lastSquare] = index[s];
pieceList[c][pt][index[lastSquare]] = lastSquare;
projects / stockfish / blobdiff