For selecting the depths in a coarse-to-fine manner, we follow the heuristics mentioned in Section 3.1, that is, we select depths which are diverse enough so as to have better coverage of all the relative tasks.
we follow a quotient between two adjacent selected tasks of 5, and select from the task which has the cardinality of 5000, then we select tasks of cardinalities around 1000, 200, 40 respectively.