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Refactor Position::pinned_pieces() to use templates

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Also better document this interesting function.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba
2008-10-23 12:59:20 +02:00
parent 2f8961beef
commit af59cb1d63
4 changed files with 49 additions and 44 deletions
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67
src/position.cpp
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@@ -296,40 +296,53 @@ void Position::copy(const Position &pos) {
}
/// Position:pinned_pieces() returns a bitboard of all pinned (against the
/// king) pieces for the given color.
/// Position:pinned_pieces<>() returns a bitboard of all pinned (against the
/// king) pieces for the given color and for the given pinner type.
template<PieceType Piece>
Bitboard Position::pinned_pieces(Color c, Square ksq) const {
Bitboard Position::pinned_pieces(Color c) const {
Bitboard b1, b2, pinned, pinners, sliders;
Square ksq = king_square(c), s;
Color them = opposite_color(c);
Square s;
Bitboard sliders, pinned = EmptyBoardBB;
if (Piece == ROOK) // Resolved at compile time
sliders = rooks_and_queens(opposite_color(c)) & RookPseudoAttacks[ksq];
else
sliders = bishops_and_queens(opposite_color(c)) & BishopPseudoAttacks[ksq];
pinned = EmptyBoardBB;
b1 = occupied_squares();
if (sliders && (sliders & ~checkersBB))
{
// Our king blockers are candidate pinned pieces
Bitboard candidate_pinned = piece_attacks<Piece>(ksq) & pieces_of_color(c);
sliders = rooks_and_queens(them) & ~checkers();
if(sliders & RookPseudoAttacks[ksq]) {
b2 = piece_attacks<ROOK>(ksq) & pieces_of_color(c);
pinners = rook_attacks_bb(ksq, b1 ^ b2) & sliders;
while(pinners) {
s = pop_1st_bit(&pinners);
pinned |= (squares_between(s, ksq) & b2);
}
// Pinners are sliders, not checkers, that give check when
// candidate pinned are removed.
Bitboard pinners = sliders & ~checkersBB;
if (Piece == ROOK)
pinners &= rook_attacks_bb(ksq, occupied_squares() ^ candidate_pinned);
else
pinners &= bishop_attacks_bb(ksq, occupied_squares() ^ candidate_pinned);
// Finally for each pinner find the corresponding pinned piece
// among the candidates.
while (pinners)
{
s = pop_1st_bit(&pinners);
pinned |= (squares_between(s, ksq) & candidate_pinned);
}
}
sliders = bishops_and_queens(them) & ~checkers();
if(sliders & BishopPseudoAttacks[ksq]) {
b2 = piece_attacks<BISHOP>(ksq) & pieces_of_color(c);
pinners = bishop_attacks_bb(ksq, b1 ^ b2) & sliders;
while(pinners) {
s = pop_1st_bit(&pinners);
pinned |= (squares_between(s, ksq) & b2);
}
}
return pinned;
}
/// Position:pinned_pieces() returns a bitboard of all pinned (against the
/// king) pieces for the given color.
Bitboard Position::pinned_pieces(Color c) const {
Square ksq = king_square(c);
return pinned_pieces<ROOK>(c, ksq) | pinned_pieces<BISHOP>(c, ksq);
}
/// Position:discovered_check_candidates() returns a bitboard containing all
/// pieces for the given side which are candidates for giving a discovered
/// check. The code is almost the same as the function for finding pinned