test_atomic_relaxed_arm.cpp

#include <vector>
#include <iostream>
#include <iomanip>
#include <thread>
#include <atomic>
#include <mutex>
#include <condition_variable>
#include <memory>

int main(int argc, char *argv[])
{
    const auto ORDER = argc < 2 ? std::memory_order_relaxed : std::memory_order_seq_cst;
    std::cout << "Memory order: " << int(ORDER) << '\n';

    std::atomic_long var{0};
    const auto iters = 100'000'000;
    const auto thrds = 10;
    const long expected = iters * thrds;
    using Atom = std::atomic<uint8_t>;
    auto atoms = std::make_unique<Atom[]>(expected);

    std::cout << "Iterating " << iters << " times with " << thrds << " threads ...\n";
    const auto f = [&var, &atoms, ORDER]() {
        for (int i = 0; i < iters; ++i)
            atoms[var.fetch_add(1, ORDER)].fetch_add(1, ORDER);
    };
    std::vector<std::thread> v;
    for (int i = 0; i < thrds; ++i)
        v.emplace_back(f);
    for (auto& t : v)
        t.join();

    std::cout << "Final value: " << var.load() << "   is expected: " << std::boolalpha << (var.load() == expected) << '\n';
    std::cout << "Scanning ... " << std::flush;
    long failed = -1;
    for (int64_t i = 0; i < expected; ++i) {
        if (atoms[i].load() != 1) {
            failed = i;
            break;
        }
    }
    if (failed < 0)
        std::cout << "All ok!\n";
    else
        std::cout << "Failed at " << failed << '\n';
    return 0;
}