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.

[edit] 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

[edit] See also

hash

(C++11)

hash function object
(class template)

Language
Standard library headers
Concepts
Utilities library
Strings library
Containers library
Algorithms library
Iterators 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>