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Super fast hidden_checkers()

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Rewritten hidden_checkers() to avoid calling
sliders attacks functions but just a much
faster squares_between()

Also a good code semplification.

No functional change.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba
2009-03-04 12:04:28 +01:00
parent 02cd96e4c2
commit 68e711aac6
2 changed files with 35 additions and 58 deletions
Download Patch File Download Diff File Expand all files Collapse all files

81
src/position.cpp
View File

@@ -320,71 +320,40 @@ void Position::copy(const Position &pos) {
}
/// Position:pinned_pieces() returns a bitboard of all pinned (against the
/// king) pieces for the given color.
Bitboard Position::pinned_pieces(Color c) const {
Bitboard p;
Square ksq = king_square(c);
return hidden_checks<ROOK, true>(c, ksq, p) | hidden_checks<BISHOP, true>(c, ksq, p);
}
/// 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
/// pieces.
Bitboard Position::discovered_check_candidates(Color c) const {
Bitboard p;
Square ksq = king_square(opposite_color(c));
return hidden_checks<ROOK, false>(c, ksq, p) | hidden_checks<BISHOP, false>(c, ksq, p);
}
/// Position:hidden_checks<>() returns a bitboard of all pinned (against the
/// 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 pinned pieces of opposite color
/// that are, indeed, the pieces candidate for a discovery check.
/// template parameter FindPinned is false, the pieces of the given color
/// candidate for a discovery check against the enemy king.
/// Note that checkersBB bitboard must be already updated.
template<PieceType Piece, bool FindPinned>
Bitboard Position::hidden_checks(Color c, Square ksq, Bitboard& pinners) const {
Square s;
Bitboard sliders, result = EmptyBoardBB;
template<bool FindPinned>
Bitboard Position::hidden_checkers(Color c) const {
if (Piece == ROOK) // Resolved at compile time
sliders = rooks_and_queens(FindPinned ? opposite_color(c) : c) & RookPseudoAttacks[ksq];
else
sliders = bishops_and_queens(FindPinned ? opposite_color(c) : c) & BishopPseudoAttacks[ksq];
Bitboard pinners, result = EmptyBoardBB;
if (sliders && (!FindPinned || (sliders & ~st->checkersBB)))
// 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 = (rooks_and_queens(FindPinned ? opposite_color(c) : c) & RookPseudoAttacks[ksq])
| (bishops_and_queens(FindPinned ? opposite_color(c) : c) & BishopPseudoAttacks[ksq]);
if (FindPinned && pinners)
pinners &= ~st->checkersBB;
while (pinners)
{
// King blockers are candidate pinned pieces
Bitboard candidate_pinned = piece_attacks<Piece>(ksq) & pieces_of_color(c);
Square s = pop_1st_bit(&pinners);
Bitboard b = squares_between(s, ksq) & occupied_squares();
// Pinners are sliders, not checkers, that give check when
// candidate pinned are removed.
pinners = (FindPinned ? sliders & ~st->checkersBB : sliders);
assert(b);
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 (if same color of king)
// or discovery checker (if opposite color) among the candidates.
Bitboard p = pinners;
while (p)
{
s = pop_1st_bit(&p);
result |= (squares_between(s, ksq) & candidate_pinned);
}
if ( !(b & (b - 1)) // Only one bit set?
&& (b & pieces_of_color(c))) // Is an our piece?
result |= b;
}
else
pinners = EmptyBoardBB;
return result;
}

12
src/position.h
View File

@@ -312,8 +312,8 @@ private:
template<PieceType Piece>
void update_checkers(Bitboard* pCheckersBB, Square ksq, Square from, Square to, Bitboard dcCandidates);
template<PieceType Piece, bool FindPinned>
Bitboard hidden_checks(Color c, Square ksq, Bitboard& pinners) const;
template<bool FindPinned>
Bitboard hidden_checkers(Color c) const;
// Computing hash keys from scratch (for initialization and debugging)
Key compute_key() const;
@@ -566,6 +566,14 @@ inline Bitboard Position::checkers() const {
return st->checkersBB;
}
inline Bitboard Position::pinned_pieces(Color c) const {
return hidden_checkers<true>(c);
}
inline Bitboard Position::discovered_check_candidates(Color c) const {
return hidden_checkers<false>(c);
}
inline bool Position::is_check() const {
return st->checkersBB != EmptyBoardBB;
}