UUIDの衝突が起きるかテストするプログラム

uuid_test.cc

// c++ -std=c++20 -O2 uuid_test.cc
#include <chrono>
#include <iostream>
#include <thread>
#include <mutex>
#include <set>
#include <vector>
#include <uuid/uuid.h>

struct Uuid {
  uuid_t uuid;
  Uuid() = default;
  Uuid(const Uuid &other) { uuid_copy(uuid, other.uuid); }
  Uuid(const uuid_t other_uuid) { uuid_copy(uuid, other_uuid); }
  void generateInplace() { uuid_generate(uuid); }
  static Uuid generate() { Uuid wrapped; uuid_generate(wrapped.uuid); return wrapped; }
  bool operator<(const Uuid &other) const { return uuid_compare(uuid, other.uuid) < 0; }
  bool operator==(const Uuid &other) const { return uuid_compare(uuid, other.uuid) == 0; }
};

std::mutex mutex;
std::set<Uuid> set;
std::chrono::system_clock::time_point start;
std::chrono::system_clock::time_point previous;
size_t count = 0;

void gen(int id) {
    while (true) {
        uuid_t u1;
        uuid_generate(u1);
        std::lock_guard<std::mutex> lock(mutex);
        if (set.find(u1) != set.end()) {
            uuid_string_t u1str;
            uuid_unparse(u1, u1str);
            auto now = std::chrono::system_clock::now();
            auto elapsed = std::chrono::duration_cast<std::chrono::seconds>(start - previous).count();
            std::cout << id << ":" << count << "," << elapsed << "," << set.size() << "," << u1str << std::endl;
            exit(1);
        }
        set.insert(u1);
        auto size = set.size();
        if (size % 1000000 == 0) {
            count += 1;
            auto now = std::chrono::system_clock::now();
            auto elapsed = std::chrono::duration_cast<std::chrono::seconds>(now - previous).count();
            if (elapsed > 5) {
                std::cout << id << ":" << count << "," << elapsed << "," << size << ",reset" << std::endl;
                set.clear();
                now = std::chrono::system_clock::now();
            } else {
                std::cout << id << ":" << count << "," << elapsed << "," << size << std::endl;
            }
            previous = now;
        }

    }
}

int main(int argc, char *argv[])
{
    std::vector<std::thread> threads;
    previous = start = std::chrono::system_clock::now();
    for (int i = 0; i < 8; i++) {
        threads.push_back(std::thread(gen, i));
    }
    // 返ってこないからここから先は不要
    for (auto &t : threads) {
        t.join();
    }
    return 0;
}

オンメモリだとsetのサイズが3億あたりでだいぶ遅くなるので、100万個生成するのに5秒よりかかるようになったらsetをクリアしてやり直すように修正。