NAME¶

std::unordered_map::max_size - std::unordered_map::max_size

Synopsis¶

size_type max_size() const noexcept; (since C++11)

Returns the maximum number of elements the container is able to hold due to system
or library implementation limitations, i.e. std::distance(begin(), end()) for the
largest container.

Parameters¶

(none)

Return value¶

Maximum number of elements.

Complexity¶

Constant.

Notes¶

This value typically reflects the theoretical limit on the size of the container, at
most std::numeric_limits<difference_type>::max(). At runtime, the size of the
container may be limited to a value smaller than max_size() by the amount of RAM
available.

Example¶

// Run this code

#include <iostream>
#include <locale>
#include <unordered_map>

int main()
{
std::unordered_map<char, char> p;
std::unordered_map<long, char> q;

std::cout.imbue(std::locale("en_US.UTF-8"));
std::cout << std::uppercase
<< "p.max_size() = " << std::dec << p.max_size() << " = 0x"
<< std::hex << p.max_size() << '\n'
<< "q.max_size() = " << std::dec << q.max_size() << " = 0x"
<< std::hex << q.max_size() << '\n';
}

Possible output:¶

p.max_size() = 1,152,921,504,606,846,975 = 0xFFF,FFF,FFF,FFF,FFF
q.max_size() = 768,614,336,404,564,650 = 0xAAA,AAA,AAA,AAA,AAA

See also¶

size returns the number of elements
(public member function)