std::hash<std::thread::id> (3) - Linux Manuals

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

NAME

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

Synopsis

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

 This section is incomplete
 Reason: example that uses hash meaningfully

// 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