EVASION
};
- // Functions
- bool castling_is_check(const Position&, CastlingSide);
-
// Helper templates
template<CastlingSide Side>
MoveStack* generate_castle_moves(const Position&, MoveStack*);
mlist = generate_direct_checks<KNIGHT>(pos, mlist, us, dc, ksq);
mlist = generate_direct_checks<BISHOP>(pos, mlist, us, dc, ksq);
mlist = generate_direct_checks<ROOK>(pos, mlist, us, dc, ksq);
- mlist = generate_direct_checks<QUEEN>(pos, mlist, us, dc, ksq);
-
- // Castling moves that give check. Very rare but nice to have!
- if ( pos.can_castle_queenside(us)
- && (square_rank(ksq) == square_rank(pos.king_square(us)) || square_file(ksq) == FILE_D)
- && castling_is_check(pos, QUEEN_SIDE))
- mlist = generate_castle_moves<QUEEN_SIDE>(pos, mlist);
-
- if ( pos.can_castle_kingside(us)
- && (square_rank(ksq) == square_rank(pos.king_square(us)) || square_file(ksq) == FILE_F)
- && castling_is_check(pos, KING_SIDE))
- mlist = generate_castle_moves<KING_SIDE>(pos, mlist);
-
- return mlist;
+ return generate_direct_checks<QUEEN>(pos, mlist, us, dc, ksq);
}
-/// generate_evasions() generates all check evasions when the side to move is
-/// in check. Unlike the other move generation functions, this one generates
-/// only legal moves. Returns a pointer to the end of the move list.
+/// generate_evasions() generates all pseudo-legal check evasions when
+/// the side to move is in check. Returns a pointer to the end of the move list.
MoveStack* generate_evasions(const Position& pos, MoveStack* mlist, Bitboard pinned) {
assert(pos.is_ok());
assert(pos.is_check());
- Square from, to;
+ Bitboard b;
+ Square from, to, checksq;
+ int checkersCnt = 0;
Color us = pos.side_to_move();
Color them = opposite_color(us);
Square ksq = pos.king_square(us);
- Bitboard sliderAttacks = EmptyBoardBB;
Bitboard checkers = pos.checkers();
+ Bitboard sliderAttacks = EmptyBoardBB;
assert(pos.piece_on(ksq) == piece_of_color_and_type(us, KING));
-
- // The bitboard of occupied pieces without our king
- Bitboard b_noKing = pos.occupied_squares();
- clear_bit(&b_noKing, ksq);
+ assert(checkers);
// Find squares attacked by slider checkers, we will remove
- // them from the king evasions set so to avoid a couple
- // of cycles in the slow king evasions legality check loop
- // and to be able to use attackers_to().
- Bitboard b = checkers & pos.pieces(BISHOP, QUEEN);
- while (b)
+ // them from the king evasions set so to early skip known
+ // illegal moves and avoid an useless legality check later.
+ b = checkers;
+ do
{
- from = pop_1st_bit(&b);
- sliderAttacks |= bishop_attacks_bb(from, b_noKing);
- }
-
- b = checkers & pos.pieces(ROOK, QUEEN);
- while (b)
- {
- from = pop_1st_bit(&b);
- sliderAttacks |= rook_attacks_bb(from, b_noKing);
- }
-
- // Generate evasions for king, capture and non capture moves
- Bitboard enemy = pos.pieces_of_color(them);
- Bitboard b1 = pos.attacks_from<KING>(ksq) & ~pos.pieces_of_color(us) & ~sliderAttacks;
- while (b1)
- {
- // Note that we can use attackers_to() only because we have already
- // removed from b1 the squares attacked by slider checkers.
- to = pop_1st_bit(&b1);
- if (!(pos.attackers_to(to) & enemy))
- (*mlist++).move = make_move(ksq, to);
- }
-
- // Generate evasions for other pieces only if not double check. We use a
- // simple bit twiddling hack here rather than calling count_1s in order to
- // save some time (we know that pos.checkers() has at most two nonzero bits).
- if (!(checkers & (checkers - 1))) // Only one bit set?
- {
- Square checksq = first_1(checkers);
+ checkersCnt++;
+ checksq = pop_1st_bit(&b);
assert(pos.color_of_piece_on(checksq) == them);
- // Generate captures of the checking piece
-
- // Pawn captures
- b1 = pos.attacks_from<PAWN>(checksq, them) & pos.pieces(PAWN, us) & ~pinned;
- while (b1)
+ switch (pos.type_of_piece_on(checksq))
{
- from = pop_1st_bit(&b1);
- if (relative_rank(us, checksq) == RANK_8)
- {
- (*mlist++).move = make_promotion_move(from, checksq, QUEEN);
- (*mlist++).move = make_promotion_move(from, checksq, ROOK);
- (*mlist++).move = make_promotion_move(from, checksq, BISHOP);
- (*mlist++).move = make_promotion_move(from, checksq, KNIGHT);
- } else
- (*mlist++).move = make_move(from, checksq);
+ case BISHOP: sliderAttacks |= BishopPseudoAttacks[checksq]; break;
+ case ROOK: sliderAttacks |= RookPseudoAttacks[checksq]; break;
+ case QUEEN:
+ // In case of a queen remove also squares attacked in the other direction to
+ // avoid possible illegal moves when queen and king are on adjacent squares.
+ if (direction_is_straight(checksq, ksq))
+ sliderAttacks |= RookPseudoAttacks[checksq] | pos.attacks_from<BISHOP>(checksq);
+ else
+ sliderAttacks |= BishopPseudoAttacks[checksq] | pos.attacks_from<ROOK>(checksq);
+ default:
+ break;
}
+ } while (b);
+
+ // Generate evasions for king, capture and non capture moves
+ b = pos.attacks_from<KING>(ksq) & ~pos.pieces_of_color(us) & ~sliderAttacks;
+ from = ksq;
+ SERIALIZE_MOVES(b);
- // Pieces captures
- b1 = ( (pos.attacks_from<KNIGHT>(checksq) & pos.pieces(KNIGHT, us))
- | (pos.attacks_from<BISHOP>(checksq) & pos.pieces(BISHOP, QUEEN, us))
- | (pos.attacks_from<ROOK>(checksq) & pos.pieces(ROOK, QUEEN, us)) ) & ~pinned;
+ // Generate evasions for other pieces only if not double check
+ if (checkersCnt > 1)
+ return mlist;
- while (b1)
+ Bitboard target = squares_between(checksq, ksq);
+
+ // Pawn captures
+ b = pos.attacks_from<PAWN>(checksq, them) & pos.pieces(PAWN, us) & ~pinned;
+ while (b)
+ {
+ from = pop_1st_bit(&b);
+ if (relative_rank(us, checksq) == RANK_8)
{
- from = pop_1st_bit(&b1);
+ (*mlist++).move = make_promotion_move(from, checksq, QUEEN);
+ (*mlist++).move = make_promotion_move(from, checksq, ROOK);
+ (*mlist++).move = make_promotion_move(from, checksq, BISHOP);
+ (*mlist++).move = make_promotion_move(from, checksq, KNIGHT);
+ } else
(*mlist++).move = make_move(from, checksq);
- }
+ }
- // Blocking check evasions are possible only if the checking piece is a slider
- if (sliderAttacks)
- {
- Bitboard blockSquares = squares_between(checksq, ksq);
-
- assert((pos.occupied_squares() & blockSquares) == EmptyBoardBB);
-
- if (blockSquares)
- {
- mlist = generate_piece_evasions<PAWN>(pos, mlist, us, blockSquares, pinned);
- mlist = generate_piece_evasions<KNIGHT>(pos, mlist, us, blockSquares, pinned);
- mlist = generate_piece_evasions<BISHOP>(pos, mlist, us, blockSquares, pinned);
- mlist = generate_piece_evasions<ROOK>(pos, mlist, us, blockSquares, pinned);
- mlist = generate_piece_evasions<QUEEN>(pos, mlist, us, blockSquares, pinned);
- }
- }
+ // Pawn blocking evasions (possible only if the checking piece is a slider)
+ if (sliderAttacks)
+ mlist = generate_piece_evasions<PAWN>(pos, mlist, us, target, pinned);
+
+ // Add the checking piece to the target squares
+ target |= checkers;
+
+ // Captures and blocking evasions for the other pieces
+ mlist = generate_piece_moves<KNIGHT>(pos, mlist, us, target);
+ mlist = generate_piece_moves<BISHOP>(pos, mlist, us, target);
+ mlist = generate_piece_moves<ROOK>(pos, mlist, us, target);
+ mlist = generate_piece_moves<QUEEN>(pos, mlist, us, target);
+
+ // Finally, the special case of en passant captures. An en passant
+ // capture can only be a check evasion if the check is not a discovered
+ // check. If pos.ep_square() is set, the last move made must have been
+ // a double pawn push. If, furthermore, the checking piece is a pawn,
+ // an en passant check evasion may be possible.
+ if (pos.ep_square() != SQ_NONE && (checkers & pos.pieces(PAWN, them)))
+ {
+ to = pos.ep_square();
+ b = pos.attacks_from<PAWN>(to, them) & pos.pieces(PAWN, us);
+
+ // The checking pawn cannot be a discovered (bishop) check candidate
+ // otherwise we were in check also before last double push move.
+ assert(!bit_is_set(pos.discovered_check_candidates(them), checksq));
+ assert(count_1s(b) == 1 || count_1s(b) == 2);
- // Finally, the special case of en passant captures. An en passant
- // capture can only be a check evasion if the check is not a discovered
- // check. If pos.ep_square() is set, the last move made must have been
- // a double pawn push. If, furthermore, the checking piece is a pawn,
- // an en passant check evasion may be possible.
- if (pos.ep_square() != SQ_NONE && (checkers & pos.pieces(PAWN, them)))
+ b &= ~pinned;
+ while (b)
{
- to = pos.ep_square();
- b1 = pos.attacks_from<PAWN>(to, them) & pos.pieces(PAWN, us);
-
- // The checking pawn cannot be a discovered (bishop) check candidate
- // otherwise we were in check also before last double push move.
- assert(!bit_is_set(pos.discovered_check_candidates(them), checksq));
- assert(count_1s(b1) == 1 || count_1s(b1) == 2);
-
- b1 &= ~pinned;
- while (b1)
- {
- from = pop_1st_bit(&b1);
- // Move is always legal because checking pawn is not a discovered
- // check candidate and our capturing pawn has been already tested
- // against pinned pieces.
- (*mlist++).move = make_ep_move(from, to);
- }
+ from = pop_1st_bit(&b);
+ // Move is always legal because checking pawn is not a discovered
+ // check candidate and our capturing pawn has been already tested
+ // against pinned pieces.
+ (*mlist++).move = make_ep_move(from, to);
}
}
return mlist;
assert(pos.is_ok());
+ MoveStack* last;
Bitboard pinned = pos.pinned_pieces(pos.side_to_move());
- if (pos.is_check())
- return generate_evasions(pos, mlist, pinned);
-
// Generate pseudo-legal moves
- MoveStack* last = generate_captures(pos, mlist);
- last = generate_noncaptures(pos, last);
+ if (pos.is_check())
+ last = generate_evasions(pos, mlist, pinned);
+ else {
+ last = generate_captures(pos, mlist);
+ last = generate_noncaptures(pos, last);
+ }
if (pseudoLegal)
return last;
}
return mlist;
}
-
- bool castling_is_check(const Position& pos, CastlingSide side) {
-
- // After castling opponent king is attacked by the castled rook?
- File rookFile = (side == QUEEN_SIDE ? FILE_D : FILE_F);
- Color us = pos.side_to_move();
- Square ksq = pos.king_square(us);
- Bitboard occ = pos.occupied_squares();
-
- clear_bit(&occ, ksq); // Remove our king from the board
- Square rsq = make_square(rookFile, square_rank(ksq));
- return bit_is_set(rook_attacks_bb(rsq, occ), pos.king_square(opposite_color(us)));
- }
}
projects / stockfish / blobdiff