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Teach check_blockers to check also non-king pieces

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This is a prerequisite for next patch

No functional change.
This commit is contained in:
Stéphane Nicolet 2016-05-21 10:05:19 +02:00 • committed by Marco Costalba
parent ab0f4c0353
commit abac509ccb
2 changed files with 15 additions and 16 deletions
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25
src/position.cpp
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@ -420,28 +420,27 @@ Phase Position::game_phase() const {
}
/// Position::check_blockers() returns a bitboard of all the pieces with color
/// 'c' that are blocking check on the king with color 'kingColor'. A piece
/// blocks a check if removing that piece from the board would result in a
/// position where the king is in check. A check blocking piece can be either a
/// pinned or a discovered check piece, according if its color 'c' is the same
/// or the opposite of 'kingColor'.
/// Position::slider_blockers() returns a bitboard of all the pieces in 'target' that
/// are blocking attacks on the square 's' from 'sliders'. A piece blocks a slider
/// if removing that piece from the board would result in a position where square 's'
/// is attacked. For example, a king-attack blocking piece can be either a pinned or
/// a discovered check piece, according if its color is the opposite or the same of
/// the color of the slider.
Bitboard Position::check_blockers(Color c, Color kingColor) const {
Bitboard Position::slider_blockers(Bitboard target, Bitboard sliders, Square s) const {
Bitboard b, pinners, result = 0;
Square ksq = square<KING>(kingColor);
// Pinners are sliders that give check when a pinned piece is removed
pinners = ( (pieces( ROOK, QUEEN) & PseudoAttacks[ROOK ][ksq])
| (pieces(BISHOP, QUEEN) & PseudoAttacks[BISHOP][ksq])) & pieces(~kingColor);
// Pinners are sliders that attack 's' when a pinned piece is removed
pinners = ( (PseudoAttacks[ROOK ][s] & pieces(QUEEN, ROOK))
| (PseudoAttacks[BISHOP][s] & pieces(QUEEN, BISHOP))) & sliders;
while (pinners)
{
b = between_bb(ksq, pop_lsb(&pinners)) & pieces();
b = between_bb(s, pop_lsb(&pinners)) & pieces();
if (!more_than_one(b))
result |= b & pieces(c);
result |= b & target;
}
return result;
}

6
src/position.h
View file

@ -131,6 +131,7 @@ public:
Bitboard attacks_from(Piece pc, Square s) const;
template<PieceType> Bitboard attacks_from(Square s) const;
template<PieceType> Bitboard attacks_from(Square s, Color c) const;
Bitboard slider_blockers(Bitboard target, Bitboard sliders, Square s) const;
// Properties of moves
bool legal(Move m, Bitboard pinned) const;
@ -186,7 +187,6 @@ private:
void set_state(StateInfo* si) const;
// Other helpers
Bitboard check_blockers(Color c, Color kingColor) const;
void put_piece(Color c, PieceType pt, Square s);
void remove_piece(Color c, PieceType pt, Square s);
void move_piece(Color c, PieceType pt, Square from, Square to);
@ -311,11 +311,11 @@ inline Bitboard Position::checkers() const {
}
inline Bitboard Position::discovered_check_candidates() const {
return check_blockers(sideToMove, ~sideToMove);
return slider_blockers(pieces(sideToMove), pieces(sideToMove), square<KING>(~sideToMove));
}
inline Bitboard Position::pinned_pieces(Color c) const {
return check_blockers(c, c);
return slider_blockers(pieces(c), pieces(~c), square<KING>(c));
}
inline bool Position::pawn_passed(Color c, Square s) const {