- || relative_rank(weakerSide, kingSq) <= relative_rank(weakerSide, pawnSq))
- return SCALE_FACTOR_DRAW;
- }
- }
-
- // All pawns on same B or G file? Then potential draw
- if ( (pawnFile == FILE_B || pawnFile == FILE_G)
- && !(pos.pieces(PAWN) & ~file_bb(pawnFile))
- && pos.non_pawn_material(weakerSide) == 0
- && pos.count<PAWN>(weakerSide) >= 1)
- {
- // Get weakerSide pawn that is closest to home rank
- Square weakerPawnSq = backmost_sq(weakerSide, pos.pieces(weakerSide, PAWN));
-
- Square strongerKingSq = pos.king_square(strongerSide);
- Square weakerKingSq = pos.king_square(weakerSide);
- Square bishopSq = pos.list<BISHOP>(strongerSide)[0];
-
- // Potential for a draw if our pawn is blocked on the 7th rank
- // the bishop cannot attack it or they only have one pawn left
- if ( relative_rank(strongerSide, weakerPawnSq) == RANK_7
- && (pos.pieces(strongerSide, PAWN) & (weakerPawnSq + pawn_push(weakerSide)))
- && (opposite_colors(bishopSq, weakerPawnSq) || pos.count<PAWN>(strongerSide) == 1))
- {
- int strongerKingDist = square_distance(weakerPawnSq, strongerKingSq);
- int weakerKingDist = square_distance(weakerPawnSq, weakerKingSq);
-
- // Draw if the weak king is on it's back two ranks, within 2
- // squares of the blocking pawn and the strong king is not
- // closer. (I think this rule only fails in practically
- // unreachable positions such as 5k1K/6p1/6P1/8/8/3B4/8/8 w
- // and positions where qsearch will immediately correct the
- // problem such as 8/4k1p1/6P1/1K6/3B4/8/8/8 w)
- if ( relative_rank(strongerSide, weakerKingSq) >= RANK_7
- && weakerKingDist <= 2
- && weakerKingDist <= strongerKingDist)