Simple generators benchmark

bench_generators.cpp

// https://godbolt.org/z/b9s5cxPao

#include <generator>
#include <utility>

auto generator_baseline() -> int {
    static THREAD_LOCAL auto i = 0;
    return i++;
}

// c++20 coroutines
auto generator_coroutines() noexcept(true) -> std::generator<int> {
    for (auto i = 0;; ++i) {
        co_yield i;
    }
}

auto generator_goto() -> int {
    if (static THREAD_LOCAL auto state = 0; std::exchange(state, 1)) {
        goto resume;
    }

    for (static THREAD_LOCAL auto i = 0;; ++i) {
        return i;
        resume:;
    }
}

// computed-goto - gnu::extension
auto generator_computed_goto() {
    static THREAD_LOCAL auto label = &&init;
    goto *label;
    init:;
    for (static THREAD_LOCAL auto i = 0;; ++i) {
        label = &&resume;
        return i;
        resume:;
    }
};

// duff's device
auto generator_switch() -> int {
    switch (static THREAD_LOCAL auto state = 0; state) {
        case 0:
            state = 1;
            for (static THREAD_LOCAL auto i = 0;; ++i) {
                return i;
        case 1:;
            }
    }
    return {};
}

auto generator_goto_lambda = [i = 0]() mutable -> int {
    if (static THREAD_LOCAL auto state = 0; std::exchange(state, 1)) {
        goto resume;
    }

    for (i = 0;; ++i) {
        return i;
        resume:;
    }
};

// computed-goto - gnu::extension
auto generator_computed_goto_lambda = [i = 0]() mutable -> int {
    static THREAD_LOCAL auto label = &&init;
    goto *label;
    init:;
    for (i = 0;; ++i) {
        label = &&resume;
        return i;
        resume:;
    }
};

#define ANKERL_NANOBENCH_IMPLEMENT
#include <nanobench.h>

int main() {
    static constexpr auto iterations = 1'00'000'000;
    ankerl::nanobench::Bench().minEpochIterations(iterations).run("generator_baseline", [&] { ankerl::nanobench::doNotOptimizeAway(generator_baseline()); });
    auto gen = generator_coroutines();
    auto it = gen.begin();
    ankerl::nanobench::Bench().minEpochIterations(iterations).run("generator_coroutines", [&] { ankerl::nanobench::doNotOptimizeAway(*it); it++; });
    ankerl::nanobench::Bench().minEpochIterations(iterations).run("generator_goto", [&] { ankerl::nanobench::doNotOptimizeAway(generator_goto()); });
    ankerl::nanobench::Bench().minEpochIterations(iterations).run("generator_computed_goto", [&] { ankerl::nanobench::doNotOptimizeAway(generator_computed_goto()); });
    ankerl::nanobench::Bench().minEpochIterations(iterations).run("generator_switch", [&] { ankerl::nanobench::doNotOptimizeAway(generator_switch()); });
    ankerl::nanobench::Bench().minEpochIterations(iterations).run("generator_goto_lambda", [&] { ankerl::nanobench::doNotOptimizeAway(generator_goto_lambda()); });
    ankerl::nanobench::Bench().minEpochIterations(iterations).run("generator_computed_goto_lambda", [&] { ankerl::nanobench::doNotOptimizeAway(generator_computed_goto_lambda()); });
}