Why don't unordered containers provide an interface for defining minimum load factor?

Question

I was trying to understand why hash table (unordered containers such as unordered_map or unordered_set) don't provide an interface for querying or setting minimum load factor.

Say c is a unordered_set, I can use

c.max_load_factor()

for querying

and

c.max_load_factor(val)

for setting.

Why doesn't C++11 provide an interface for querying min_load_factor? Are there implementation details, which would explain?

Also, C++ STL by Josuttis, mentions that:

The minimum load factor, which is used to force rehashing when the number of elements in the container shrinks cannot be influenced.

Answer 1

The load factor on an unordered_map affects the probability of collision in the hash table. For example,the probability of two elements being located in the same bucket. The container uses the value of max_load_factor as the threshold that forces an increase in the number of buckets and thus causing a rehash.

There is no such thing as a user-controllable minimum load factor since it should respect the number of elements already in the container.