future benchmark

future.cpp

#include <stdint.h>
#include <future>
#include <random>
#include <vector>
#include <benchmark/benchmark.h>

static uint_fast32_t long_running_task() {
    std::mt19937 gen{std::random_device{}()};
    gen.discard(1000);
    return gen();
}

static void bench_async(benchmark::State& state) {
    using namespace std;
    for (auto _ : state) {
        (void)_;
        vector<future<uint_fast32_t>> futures(1000000);
        for (auto& f : futures) {
            f = async([] { return long_running_task(); });
        }

        for (auto& f : futures) {
            f.wait();
        }
    }
}

BENCHMARK(bench_async);

BENCHMARK_MAIN();