std::hash<std::thread::id>

Defined in header `<thread>`
template<> struct hash<std::thread::id>;		(since C++11)

The template specialization of std::hash for the std::thread::id class allows users to obtain hashes of the identifiers of threads.

Example

Run this code

#include <iostream>
#include <thread>
#include <chrono>
#include <vector>
using namespace std::chrono_literals;
void foo()
{
    std::this_thread::sleep_for(10ms);
}
 
int main()
{
    std::vector<std::thread> v;
    for(int n = 0; n < 4; ++n)
        v.emplace_back(foo);
 
    std::hash<std::thread::id> hasher;
    for(auto& t : v) {
        std::cout << "thread " << t.get_id() << " hashes to " << hasher(t.get_id()) << '\n';
        t.join();
    }
}

Possible output:

thread 139786440144640 hashes to 8905351942358389397
thread 139786431751936 hashes to 9222844670065909738
thread 139786423359232 hashes to 18199000599186780501
thread 139786414966528 hashes to 15386662774029264672

Language
Standard Library Headers
Freestanding and hosted implementations
Named requirements
Language support library
Concepts library (C++20)
Diagnostics library
Utilities library
Strings library
Containers library
Iterators library
Ranges library (C++20)
Algorithms library
Numerics library
Input/output library
Localizations library
Regular expressions library (C++11)
Atomic operations library (C++11)
Thread support library (C++11)
Filesystem library (C++17)
Technical Specifications

Member classes
thread::id
Member functions
thread::thread
thread::~thread
thread::operator=
Observers
thread::joinable
thread::get_id
thread::native_handle
thread::hardware_concurrency
Operations
thread::join
thread::detach
thread::swap
Non-member functions
std::swap

Member functions
id::id
Non-member functions
operator==operator!=operator<operator<=operator>operator>=
operator<<
Helper classes
std::hash<std::thread::id>

std::hash<std::thread::id>

Example

See also