multimap get_allocator() function in C++ STL

In this article we will be discussing the working, syntax, and examples of multimap::get_allocator() function in C++ STL.

What is Multimap in C++ STL?

Multimaps are the associative containers, which are similar to map containers. It also facilitates to store the elements formed by a combination of key-value and mapped value in a specific order. In a multimap container there can be multiple elements associated with the same key. The data is internally always sorted with the help of its associated keys.

What is multimap::get_allocator()?

multimap::get_allocator() function is an inbuilt function in C++ STL, which is defined in <map> header file. get_allocator() is used to allocate the memory chunks to a multimap container. This function returns a copy of the allocator object of the container associated with it.

An allocator is an object which is responsible for dynamically memory allocation of a container.

Syntax

multi_name.get_allocator();

Parameters

The function accepts no parameter.

Return value

This function returns the allocator of the container associated.

Input 

int *Ptr; std::multimap<int> newmap; newmap.insert(make_pair(‘A’, 22)); newmap.insert(make_pair(‘B’, 78)); newmap.insert(make_pair(‘C’, 66)); newmap.insert(make_pair(‘D’, 81)); Ptr = mymap.get_allocator().allocate(4);

Output 

ptr = A:22 B:78 C:66 D:81

Example

 Live Demo

#include <iostream> #include <map> using namespace std; int main(){    int arrsize;    multimap<char, int> mul;    pair<const char, int>* pr;    pr = mul.get_allocator().allocate(15);    // assign some values to array    arrsize = sizeof(multimap<char, int>::value_type) * 10;    cout << "Size of the allocated array is: "<< arrsize << " bytes.\n";    mul.get_allocator().deallocate(pr, 5);    return 0; }

Output

If we run the above code it will generate the following output −

Size of the allocated array is: 80 bytes.

Example

 Live Demo

#include <iostream> #include <map> using namespace std; int main(){    int arrsize;    multimap<char, int> mul;    pair<const char, int>* pr;    pr = mul.get_allocator().allocate(2);    // assign some values to array    arrsize = sizeof(multimap<char, int>::value_type) * 5;    cout << "Size of the allocated array is: "<< arrsize << " bytes.\n";    mul.get_allocator().deallocate(pr, 5);    return 0; }

Output

If we run the above code it will generate the following output −

Size of the allocated array is: 40 bytes.