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Refactor Position::pinned_pieces() to use templates
Also better document this interesting function. Signed-off-by: Marco Costalba <mcostalba@gmail.com>
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2f8961beef
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4 changed files with 49 additions and 44 deletions
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@ -150,26 +150,16 @@ extern Bitboard QueenPseudoAttacks[64];
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/// Functions for testing whether a given bit is set in a bitboard, and for
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/// setting and clearing bits.
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inline Bitboard set_mask_bb(Square s) {
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// return 1ULL << s;
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return SetMaskBB[s];
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}
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inline Bitboard clear_mask_bb(Square s) {
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// return ~set_mask_bb(s);
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return ClearMaskBB[s];
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}
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inline Bitboard bit_is_set(Bitboard b, Square s) {
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return b & set_mask_bb(s);
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return b & SetMaskBB[s];
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}
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inline void set_bit(Bitboard *b, Square s) {
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*b |= set_mask_bb(s);
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*b |= SetMaskBB[s];
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}
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inline void clear_bit(Bitboard *b, Square s) {
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*b &= clear_mask_bb(s);
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*b &= ClearMaskBB[s];
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}
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@ -778,7 +778,7 @@ namespace {
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while (b)
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{
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Square from, to = pop_1st_bit(&b);
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if (!(escapeSquares & ~queen_attacks_bb(to, occ & clear_mask_bb(s))))
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if (!(escapeSquares & ~queen_attacks_bb(to, occ & ClearMaskBB[s])))
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{
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// We have a mate, unless the queen is pinned or there
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// is an X-ray attack through the queen.
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@ -787,8 +787,8 @@ namespace {
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from = p.piece_list(them, QUEEN, i);
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if ( bit_is_set(p.piece_attacks<QUEEN>(from), to)
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&& !bit_is_set(p.pinned_pieces(them), from)
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&& !(rook_attacks_bb(to, occ & clear_mask_bb(from)) & p.rooks_and_queens(us))
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&& !(rook_attacks_bb(to, occ & clear_mask_bb(from)) & p.rooks_and_queens(us)))
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&& !(rook_attacks_bb(to, occ & ClearMaskBB[from]) & p.rooks_and_queens(us))
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&& !(rook_attacks_bb(to, occ & ClearMaskBB[from]) & p.rooks_and_queens(us)))
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ei.mateThreat[them] = make_move(from, to);
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}
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@ -296,40 +296,53 @@ void Position::copy(const Position &pos) {
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}
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/// Position:pinned_pieces() returns a bitboard of all pinned (against the
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/// king) pieces for the given color.
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/// Position:pinned_pieces<>() returns a bitboard of all pinned (against the
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/// king) pieces for the given color and for the given pinner type.
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template<PieceType Piece>
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Bitboard Position::pinned_pieces(Color c, Square ksq) const {
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Bitboard Position::pinned_pieces(Color c) const {
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Bitboard b1, b2, pinned, pinners, sliders;
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Square ksq = king_square(c), s;
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Color them = opposite_color(c);
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Square s;
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Bitboard sliders, pinned = EmptyBoardBB;
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pinned = EmptyBoardBB;
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b1 = occupied_squares();
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if (Piece == ROOK) // Resolved at compile time
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sliders = rooks_and_queens(opposite_color(c)) & RookPseudoAttacks[ksq];
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else
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sliders = bishops_and_queens(opposite_color(c)) & BishopPseudoAttacks[ksq];
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sliders = rooks_and_queens(them) & ~checkers();
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if(sliders & RookPseudoAttacks[ksq]) {
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b2 = piece_attacks<ROOK>(ksq) & pieces_of_color(c);
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pinners = rook_attacks_bb(ksq, b1 ^ b2) & sliders;
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while(pinners) {
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if (sliders && (sliders & ~checkersBB))
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{
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// Our king blockers are candidate pinned pieces
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Bitboard candidate_pinned = piece_attacks<Piece>(ksq) & pieces_of_color(c);
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// Pinners are sliders, not checkers, that give check when
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// candidate pinned are removed.
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Bitboard pinners = sliders & ~checkersBB;
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if (Piece == ROOK)
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pinners &= rook_attacks_bb(ksq, occupied_squares() ^ candidate_pinned);
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else
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pinners &= bishop_attacks_bb(ksq, occupied_squares() ^ candidate_pinned);
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// Finally for each pinner find the corresponding pinned piece
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// among the candidates.
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while (pinners)
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{
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s = pop_1st_bit(&pinners);
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pinned |= (squares_between(s, ksq) & b2);
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pinned |= (squares_between(s, ksq) & candidate_pinned);
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}
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}
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sliders = bishops_and_queens(them) & ~checkers();
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if(sliders & BishopPseudoAttacks[ksq]) {
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b2 = piece_attacks<BISHOP>(ksq) & pieces_of_color(c);
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pinners = bishop_attacks_bb(ksq, b1 ^ b2) & sliders;
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while(pinners) {
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s = pop_1st_bit(&pinners);
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pinned |= (squares_between(s, ksq) & b2);
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}
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}
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return pinned;
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}
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/// Position:pinned_pieces() returns a bitboard of all pinned (against the
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/// king) pieces for the given color.
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Bitboard Position::pinned_pieces(Color c) const {
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Square ksq = king_square(c);
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return pinned_pieces<ROOK>(c, ksq) | pinned_pieces<BISHOP>(c, ksq);
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}
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/// Position:discovered_check_candidates() returns a bitboard containing all
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/// pieces for the given side which are candidates for giving a discovered
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/// check. The code is almost the same as the function for finding pinned
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@ -197,6 +197,8 @@ public:
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// Bitboards for pinned pieces and discovered check candidates
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Bitboard discovered_check_candidates(Color c) const;
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Bitboard pinned_pieces(Color c) const;
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template<PieceType Piece>
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Bitboard pinned_pieces(Color c, Square ksq) const;
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// Checking pieces
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Bitboard checkers() const;
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@ -553,7 +555,7 @@ inline Bitboard Position::checkers() const {
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}
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inline bool Position::is_check() const {
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return checkers() != EmptyBoardBB;
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return checkersBB != EmptyBoardBB;
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}
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inline bool Position::pawn_attacks_square(Color c, Square f, Square t) const {
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