Can this thread pool recursively add tasks?

[etorth]

like following one:

vit-vit/CTPL#36

[DeveloperPaul123]

In short, yes:

thread-pool/test/source/thread_pool.cpp

Lines 317 to 374 in f14f97d

	void recursive_sequential_sum(std::atomic_int32_t& counter, int count, dp::thread_pool<>& pool) {
	counter.fetch_add(count);
	if (count > 1) {
	pool.enqueue_detach(recursive_sequential_sum, std::ref(counter), count - 1, std::ref(pool));
	}
	}
	TEST_CASE("Recursive enqueue calls work correctly") {
	std::atomic_int32_t counter = 0;
	constexpr auto start = 1000;
	{
	dp::thread_pool pool(4);
	recursive_sequential_sum(counter, start, pool);
	}
	auto expected_sum = 0;
	for (int i = 0; i <= start; i++) {
	expected_sum += i;
	}
	CHECK_EQ(expected_sum, counter.load());
	}
	void recursive_parallel_sort(int* begin, int* end, int split_level, dp::thread_pool<>& pool) {
	if (split_level < 2 || end - begin < 2) {
	std::sort(begin, end);
	} else {
	const auto mid = begin + (end - begin) / 2;
	if (split_level == 2) {
	const auto future =
	pool.enqueue(recursive_parallel_sort, begin, mid, split_level / 2, std::ref(pool));
	std::sort(mid, end);
	future.wait();
	} else {
	const auto left =
	pool.enqueue(recursive_parallel_sort, begin, mid, split_level / 2, std::ref(pool));
	const auto right =
	pool.enqueue(recursive_parallel_sort, mid, end, split_level / 2, std::ref(pool));
	left.wait();
	right.wait();
	}
	std::inplace_merge(begin, mid, end);
	}
	}
	TEST_CASE("Recursive parallel sort") {
	std::vector<int> data(10000);
	// std::ranges::iota is a C++23 feature
	std::iota(data.begin(), data.end(), 0);
	std::ranges::shuffle(data, std::mt19937{std::random_device{}()});
	{
	dp::thread_pool pool(4);
	recursive_parallel_sort(data.data(), data.data() + data.size(), 4, pool);
	}
	CHECK(std::ranges::is_sorted(data));
	}

But it's a bit more complicated than that. You can easily do things incorrectly this way. The thread pool tries to ensure that it doesn't get stuck, but it's still possible to block as mentioned here: #57 (comment)

Also in the future, please open a discussion for questions instead of an issue.