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Add lsb() overload

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Helper to find least significant bit relative to
the given color.

No functional change.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Gary Linscott
2013-08-28 09:35:04 +02:00
committed by Marco Costalba
parent e6482b7d97
commit aecdbfc4a0
3 changed files with 10 additions and 17 deletions
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18
src/endgame.cpp
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@@ -443,18 +443,7 @@ ScaleFactor Endgame<KBPsK>::operator()(const Position& pos) const {
// The bishop has the wrong color, and the defending king is on the
// file of the pawn(s) or the adjacent file. Find the rank of the
// frontmost pawn.
Rank rank;
if (strongerSide == WHITE)
{
for (rank = RANK_7; !(rank_bb(rank) & pawns); rank--) {}
assert(rank >= RANK_2 && rank <= RANK_7);
}
else
{
for (rank = RANK_2; !(rank_bb(rank) & pawns); rank++) {}
rank = Rank(rank ^ 7); // HACK to get the relative rank
assert(rank >= RANK_2 && rank <= RANK_7);
}
Rank rank = relative_rank(strongerSide, lsb(weakerSide, pawns));
// If the defending king has distance 1 to the promotion square or
// is placed somewhere in front of the pawn, it's a draw.
if ( square_distance(kingSq, queeningSq) <= 1
@@ -469,9 +458,8 @@ ScaleFactor Endgame<KBPsK>::operator()(const Position& pos) const {
&& pos.non_pawn_material(weakerSide) == 0
&& pos.count<PAWN>(weakerSide) >= 1)
{
// Get weaker pawn closest to opponent's queening square
Bitboard wkPawns = pos.pieces(weakerSide, PAWN);
Square weakerPawnSq = strongerSide == WHITE ? msb(wkPawns) : lsb(wkPawns);
// Get weakerSide pawn that is closest to home rank
Square weakerPawnSq = lsb(weakerSide, pos.pieces(weakerSide, PAWN));
Square strongerKingSq = pos.king_square(strongerSide);
Square weakerKingSq = pos.king_square(weakerSide);