Что выведет: атомик, мьютекс и CAS

#include <atomic>
#include <iostream>
#include <mutex>
#include <thread>
#include <vector>

int main() {
    std::atomic<int> counter{0};
    int plain = 0;
    std::mutex m;
    std::vector<std::thread> ts;
    for (int i = 0; i < 4; ++i)
        ts.emplace_back([&] {
            for (int j = 0; j < 1000; ++j) {
                counter.fetch_add(1, std::memory_order_relaxed);
                std::lock_guard lock(m);
                ++plain;
            }
        });
    for (auto& t : ts) t.join();
    std::cout << counter.load() << ' ' << plain << '\n';

    std::atomic<int> x{5};
    int expected = 5;
    bool ok = x.compare_exchange_strong(expected, 7);
    std::cout << ok << ' ' << x.load() << ' ' << expected << '\n';
    ok = x.compare_exchange_strong(expected, 9);
    std::cout << ok << ' ' << x.load() << ' ' << expected << '\n';
}