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Simplify and micro-optimize hidden_checkers()

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No functional change.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba
2011-07-15 22:24:18 +01:00
parent a042449f5d
commit 36bb57a47e
2 changed files with 13 additions and 21 deletions
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src/position.cpp
+11 -19
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@@ -361,36 +361,28 @@ void Position::print(Move move) const {
/// Position:hidden_checkers<>() returns a bitboard of all pinned (against the
/// king) pieces for the given color and for the given pinner type. Or, when
/// template parameter FindPinned is false, the pieces of the given color
/// candidate for a discovery check against the enemy king.
/// Bitboard checkersBB must be already updated when looking for pinners.
/// king) pieces for the given color. Or, when template parameter FindPinned is
/// false, the function return the pieces of the given color candidate for a
/// discovery check against the enemy king.
template<bool FindPinned>
Bitboard Position::hidden_checkers(Color c) const {
Bitboard result = EmptyBoardBB;
// Pinned pieces protect our king, dicovery checks attack the enemy king
Bitboard b, result = EmptyBoardBB;
Bitboard pinners = pieces(FindPinned ? opposite_color(c) : c);
// Pinned pieces protect our king, dicovery checks attack
// the enemy king.
Square ksq = king_square(FindPinned ? c : opposite_color(c));
// Pinners are sliders, not checkers, that give check when candidate pinned is removed
pinners &= (pieces(ROOK, QUEEN) & RookPseudoAttacks[ksq]) | (pieces(BISHOP, QUEEN) & BishopPseudoAttacks[ksq]);
if (FindPinned && pinners)
pinners &= ~st->checkersBB;
// Pinners are sliders, that give check when candidate pinned is removed
pinners &= (pieces(ROOK, QUEEN) & RookPseudoAttacks[ksq])
| (pieces(BISHOP, QUEEN) & BishopPseudoAttacks[ksq]);
while (pinners)
{
Square s = pop_1st_bit(&pinners);
Bitboard b = squares_between(s, ksq) & occupied_squares();
b = squares_between(ksq, pop_1st_bit(&pinners)) & occupied_squares();
assert(b);
if ( !(b & (b - 1)) // Only one bit set?
&& (b & pieces(c))) // Is an our piece?
// Only one bit set and is an our piece?
if (b && !(b & (b - 1)) && (b & pieces(c)))
result |= b;
}
return result;