C++ Unordered_map Library - max_load_factor() Function

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Description

The C++ function std::unordered_map::max_load_factor() returns the current maximum load factor for the unordered_map container.

The load factor is calculated as follows −

load_factor = um.size() / um.bucket_count()

Default value of max_load_factor is 1.0

The load factor influences the probability of collision in the hash table. 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.

Declaration

Following is the declaration for std::unordered_map::max_load_factor() function form std::unordered_map header.

C++11

float max_load_factor() const noexcept;

Parameters

None

Return value

Returns the maximum load factor.

Exceptions

This member function never throws exception.

Time complexity

Constant i.e. O(1)

Example

The following example shows the usage of std::unordered_map::max_load_factor() function.

#include <iostream>
#include <unordered_map>

using namespace std;

int main(void) {
   unordered_map<char, int> um;

   cout << "max_load_factor of unordered_map = " 
      << um.max_load_factor() << endl;

   return 0;
}

Let us compile and run the above program, this will produce the following result −

max_load_factor of unordered_map = 1