Two tracklets have no overlapping in the temporal space

[fandulu]

Excuse me, referring to code, may I ask how to obtain the tracklets distance in the following cases:
(1) Two tracklets have no overlapping in the temporal space.
(2) Two tracklets are not aligned in the temporal space.

In case (1), when the distance may not be able to be calculated, how to make sure the K can be properly estimated and the assignment is correct?