diff --git a/src/endgame.cpp b/src/endgame.cpp index 5906b4d5..635ff408 100644 --- a/src/endgame.cpp +++ b/src/endgame.cpp @@ -684,25 +684,15 @@ ScaleFactor Endgame::operator()(const Position& pos) const { Square ksq = pos.king_square(weakSide); Bitboard pawns = pos.pieces(strongSide, PAWN); + Square psq = pos.list(strongSide)[0]; + + // If all pawns are ahead of the king, all pawns are on a single + // rook file and the king is within one file of the pawns then draw. + if ( !(pawns & ~in_front_bb(weakSide, rank_of(ksq))) + && !((pawns & ~FileABB) && (pawns & ~FileHBB)) + && file_distance(ksq, psq) <= 1) + return SCALE_FACTOR_DRAW; - // Are all pawns on the 'a' file? - if (!(pawns & ~FileABB)) - { - // Does the defending king block the pawns? - if ( square_distance(ksq, relative_square(strongSide, SQ_A8)) <= 1 - || ( file_of(ksq) == FILE_A - && !(in_front_bb(strongSide, rank_of(ksq)) & pawns))) - return SCALE_FACTOR_DRAW; - } - // Are all pawns on the 'h' file? - else if (!(pawns & ~FileHBB)) - { - // Does the defending king block the pawns? - if ( square_distance(ksq, relative_square(strongSide, SQ_H8)) <= 1 - || ( file_of(ksq) == FILE_H - && !(in_front_bb(strongSide, rank_of(ksq)) & pawns))) - return SCALE_FACTOR_DRAW; - } return SCALE_FACTOR_NONE; }