- || relative_rank(weakSide, kingSq) <= relative_rank(weakSide, 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(weakSide) == 0
- && pos.count<PAWN>(weakSide) >= 1)
- {
- // Get weakSide pawn that is closest to home rank
- Square weakPawnSq = backmost_sq(weakSide, pos.pieces(weakSide, PAWN));
-
- Square strongKingSq = pos.king_square(strongSide);
- Square weakKingSq = pos.king_square(weakSide);
- Square bishopSq = pos.list<BISHOP>(strongSide)[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(strongSide, weakPawnSq) == RANK_7
- && (pos.pieces(strongSide, PAWN) & (weakPawnSq + pawn_push(weakSide)))
- && (opposite_colors(bishopSq, weakPawnSq) || pos.count<PAWN>(strongSide) == 1))
- {
- int strongKingDist = square_distance(weakPawnSq, strongKingSq);
- int weakKingDist = square_distance(weakPawnSq, weakKingSq);
-
- // 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(strongSide, weakKingSq) >= RANK_7
- && weakKingDist <= 2
- && weakKingDist <= strongKingDist)