}
+/// Position:pinned_pieces() returns a bitboard of all pinned (against the
+/// king) pieces for the given color.
+
+Bitboard Position::pinned_pieces(Color c) const {
+
+ return hidden_checkers<true>(c);
+}
+
+
+/// Position:discovered_check_candidates() returns a bitboard containing all
+/// pieces for the given side which are candidates for giving a discovered
+/// check.
+
+Bitboard Position::discovered_check_candidates(Color c) const {
+
+ return hidden_checkers<false>(c);
+}
+
/// Position::attacks_to() computes a bitboard containing all pieces which
/// attacks a given square. There are two versions of this function: One
/// which finds attackers of both colors, and one which only finds the
return true;
Color us = side_to_move();
- Color them = opposite_color(us);
Square from = move_from(m);
Square ksq = king_square(us);
// after the move is made
if (move_is_ep(m))
{
+ Color them = opposite_color(us);
Square to = move_to(m);
Square capsq = make_square(square_file(to), square_rank(from));
Bitboard b = occupied_squares();
// If the moving piece is a king, check whether the destination
// square is attacked by the opponent.
if (from == ksq)
- return !(square_is_attacked(move_to(m), them));
+ return !(square_is_attacked(move_to(m), opposite_color(us)));
// A non-king move is legal if and only if it is not pinned or it
// is moving along the ray towards or away from the king.
- return ( !bit_is_set(pinned, from)
+ return ( !pinned
+ || !bit_is_set(pinned, from)
|| (direction_between_squares(from, ksq) == direction_between_squares(move_to(m), ksq)));
}
if (bit_is_set(pawn_attacks(them, ksq), to)) // Normal check?
return true;
- if ( bit_is_set(dcCandidates, from) // Discovered check?
+ if ( dcCandidates // Discovered check?
+ && bit_is_set(dcCandidates, from)
&& (direction_between_squares(from, ksq) != direction_between_squares(to, ksq)))
return true;
}
return false;
+ // Test discovered check and normal check according to piece type
case KNIGHT:
- return bit_is_set(dcCandidates, from) // Discovered check?
- || bit_is_set(piece_attacks<KNIGHT>(ksq), to); // Normal check?
+ return (dcCandidates && bit_is_set(dcCandidates, from))
+ || bit_is_set(piece_attacks<KNIGHT>(ksq), to);
case BISHOP:
- return bit_is_set(dcCandidates, from) // Discovered check?
- || bit_is_set(piece_attacks<BISHOP>(ksq), to); // Normal check?
+ return (dcCandidates && bit_is_set(dcCandidates, from))
+ || ( direction_between_squares(ksq, to) != DIR_NONE
+ && bit_is_set(piece_attacks<BISHOP>(ksq), to));
case ROOK:
- return bit_is_set(dcCandidates, from) // Discovered check?
- || bit_is_set(piece_attacks<ROOK>(ksq), to); // Normal check?
+ return (dcCandidates && bit_is_set(dcCandidates, from))
+ || ( direction_between_squares(ksq, to) != DIR_NONE
+ && bit_is_set(piece_attacks<ROOK>(ksq), to));
case QUEEN:
// Discovered checks are impossible!
assert(!bit_is_set(dcCandidates, from));
- return bit_is_set(piece_attacks<QUEEN>(ksq), to); // Normal check?
+ return ( direction_between_squares(ksq, to) != DIR_NONE
+ && bit_is_set(piece_attacks<QUEEN>(ksq), to));
case KING:
// Discovered check?
inline void Position::update_checkers(Bitboard* pCheckersBB, Square ksq, Square from,
Square to, Bitboard dcCandidates) {
- if (Piece != KING && bit_is_set(piece_attacks<Piece>(ksq), to))
+ const bool Bishop = (Piece == QUEEN || Piece == BISHOP);
+ const bool Rook = (Piece == QUEEN || Piece == ROOK);
+ const bool Slider = Bishop || Rook;
+
+ if ( ( (Bishop && bit_is_set(BishopPseudoAttacks[ksq], to))
+ || (Rook && bit_is_set(RookPseudoAttacks[ksq], to)))
+ && bit_is_set(piece_attacks<Piece>(ksq), to)) // slow, try to early skip
+ set_bit(pCheckersBB, to);
+
+ else if ( Piece != KING
+ && !Slider
+ && bit_is_set(piece_attacks<Piece>(ksq), to))
set_bit(pCheckersBB, to);
if (Piece != QUEEN && bit_is_set(dcCandidates, from))
board[to] = EMPTY;
}
- // Finally point out state pointer back to the previous state
+ // Finally point our state pointer back to the previous state
st = st->previous;
assert(is_ok());
/// Position::do_null_move makes() a "null move": It switches the side to move
/// and updates the hash key without executing any move on the board.
-void Position::do_null_move(StateInfo& newSt) {
+void Position::do_null_move(StateInfo& backupSt) {
assert(is_ok());
assert(!is_check());
// Back up the information necessary to undo the null move to the supplied
// StateInfo object. In the case of a null move, the only thing we need to
// remember is the last move made and the en passant square.
- newSt.lastMove = st->lastMove;
- newSt.epSquare = st->epSquare;
- newSt.previous = st->previous;
- st->previous = &newSt;
+ // Note that differently from normal case here backupSt is actually used as
+ // a backup storage not as a new state to be used.
+ backupSt.lastMove = st->lastMove;
+ backupSt.epSquare = st->epSquare;
+ backupSt.previous = st->previous;
+ st->previous = &backupSt;
// Save the current key to the history[] array, in order to be able to
// detect repetition draws.
assert(is_ok());
assert(!is_check());
- // Restore information from the our StateInfo object
+ // Restore information from the our backup StateInfo object
st->lastMove = st->previous->lastMove;
st->epSquare = st->previous->epSquare;
st->previous = st->previous->previous;