Example of multithreaded loop synchronization using std::barrier.

barrier_example.cpp

#include <barrier>
#include <functional>
#include <iostream>
#include <string>
#include <thread>
#include <vector>

struct Person {
  std::string name;
  int age;

  Person(const std::string& name, int age) : name(name), age(age) {}
};

void task(std::barrier<std::function<void()>>& barrier,
          const std::vector<Person>& data) {
  for (const auto& person : data) {
    std::cout << std::this_thread::get_id() << ": " << person.name << std::endl;
    barrier.arrive_and_wait();  // The barrier synchronizes processing
  }
}

// Completion function that runs on one of the threads each time all threads
// have arrived at the barrier
void finished() { std::cout << "Processed a chunk\n"; }

int main() {
  std::barrier<std::function<void()>> barrier(
      2, finished);  // 2 threads will be spawned
  std::vector<Person> chunks = {Person("John", 18), Person("Bob", 20),
                                Person("Ayush", 19)};

  std::thread t1(task, std::ref(barrier), std::ref(chunks));
  std::thread t2(task, std::ref(barrier), std::ref(chunks));
  t1.join();
  t2.join();
  std::cout << "Processing of data chunks complete...\n";
  return 0;
}