+ || 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)
+ return SCALE_FACTOR_DRAW;