+ }
+
+ // Penalize rooks which are trapped inside a king. Penalize more if
+ // king has lost right to castle
+ if (mob > 6 || ei.pi->file_is_half_open(us, f))
+ return;
+
+ Square ksq = p.king_square(us);
+ if ( square_file(ksq) >= FILE_E
+ && square_file(s) > square_file(ksq)
+ && (relative_rank(us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
+ {
+ // Is there a half-open file between the king and the edge of the board?
+ if (!ei.pi->has_open_file_to_right(us, square_file(ksq)))
+ ei.mgValue -= p.can_castle(us)? Sign[us] * ((TrappedRookPenalty - mob * 16) / 2)
+ : Sign[us] * (TrappedRookPenalty - mob * 16);
+ }
+ else if ( square_file(ksq) <= FILE_D
+ && square_file(s) < square_file(ksq)
+ && (relative_rank(us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
+ {
+ // Is there a half-open file between the king and the edge of the board?
+ if (!ei.pi->has_open_file_to_left(us, square_file(ksq)))
+ ei.mgValue -= p.can_castle(us)? Sign[us] * ((TrappedRookPenalty - mob * 16) / 2)
+ : Sign[us] * (TrappedRookPenalty - mob * 16);