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Simplify slider_blocker calculation

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Now that classical evaluation was removed, we can adapt this method
to the needs of set_check_info.

STC:
2.95 (-2.94,2.94) <-1.75,0.25>
Total: 298176 W: 75802 L: 75868 D: 146506
Ptnml(0-2): 908, 33608, 80192, 33402, 978
https://tests.stockfishchess.org/tests/view/64e70b899009777747557b43

closes https://github.com/official-stockfish/Stockfish/pull/4753

no functional change
This commit is contained in:
pb00067 2023-08-17 14:31:05 +02:00 • committed by Stéphane Nicolet
parent 4f7fe255c7
commit 1f7ff8406d
2 changed files with 16 additions and 20 deletions
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34
src/position.cpp
View file

@ -321,8 +321,8 @@ void Position::set_castling_right(Color c, Square rfrom) {
void Position::set_check_info() const { void Position::set_check_info() const {
st->blockersForKing[WHITE] = slider_blockers(pieces(BLACK), square<KING>(WHITE), st->pinners[BLACK]); update_slider_blockers(WHITE);
st->blockersForKing[BLACK] = slider_blockers(pieces(WHITE), square<KING>(BLACK), st->pinners[WHITE]); update_slider_blockers(BLACK);
Square ksq = square<KING>(~sideToMove); Square ksq = square<KING>(~sideToMove);
@ -443,37 +443,33 @@ string Position::fen() const {
return ss.str(); return ss.str();
} }
/// update_slider_blockers() calculates st->blockersForKing[c] and st->pinners[~c],
/// which store respectively the pieces preventing king of color c from being in check
/// and the slider pieces of color ~c pinning pieces of color c to the king.
void Position::update_slider_blockers(Color c) const {
/// Position::slider_blockers() returns a bitboard of all the pieces (both colors) Square ksq = square<KING>(c);
/// 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::slider_blockers(Bitboard sliders, Square s, Bitboard& pinners) const { st->blockersForKing[c] = 0;
st->pinners[~c] = 0;
Bitboard blockers = 0;
pinners = 0;
// Snipers are sliders that attack 's' when a piece and other snipers are removed // Snipers are sliders that attack 's' when a piece and other snipers are removed
Bitboard snipers = ( (attacks_bb< ROOK>(s) & pieces(QUEEN, ROOK)) Bitboard snipers = ( (attacks_bb< ROOK>(ksq) & pieces(QUEEN, ROOK))
| (attacks_bb<BISHOP>(s) & pieces(QUEEN, BISHOP))) & sliders; | (attacks_bb<BISHOP>(ksq) & pieces(QUEEN, BISHOP))) & pieces(~c);
Bitboard occupancy = pieces() ^ snipers; Bitboard occupancy = pieces() ^ snipers;
while (snipers) while (snipers)
{ {
Square sniperSq = pop_lsb(snipers); Square sniperSq = pop_lsb(snipers);
Bitboard b = between_bb(s, sniperSq) & occupancy; Bitboard b = between_bb(ksq, sniperSq) & occupancy;
if (b && !more_than_one(b)) if (b && !more_than_one(b))
{ {
blockers |= b; st->blockersForKing[c] |= b;
if (b & pieces(color_of(piece_on(s)))) if (b & pieces(c))
pinners |= sniperSq; st->pinners[~c] |= sniperSq;
} }
} }
return blockers;
} }

2
src/position.h
View file

@ -114,7 +114,7 @@ public:
// Attacks to/from a given square // Attacks to/from a given square
Bitboard attackers_to(Square s) const; Bitboard attackers_to(Square s) const;
Bitboard attackers_to(Square s, Bitboard occupied) const; Bitboard attackers_to(Square s, Bitboard occupied) const;
Bitboard slider_blockers(Bitboard sliders, Square s, Bitboard& pinners) const; void update_slider_blockers(Color c) const;
template<PieceType Pt> Bitboard attacks_by(Color c) const; template<PieceType Pt> Bitboard attacks_by(Color c) const;
// Properties of moves // Properties of moves