{

public:

/// Initialise to a number of threads equal to the number of cores

/// on the current machine.

static_thread_pool();

/// Construct a thread pool with the specified number of threads.

///

/// \param threadCount

/// The number of threads in the pool that will be used to execute work.

explicit static_thread_pool(std::uint32_t threadCount);

~static_thread_pool();

class schedule_operation

{

public:

schedule_operation(static_thread_pool* tp) noexcept : m_threadPool(tp) {}

bool await_ready() noexcept { return false; }

void await_suspend(cppcoro::coroutine_handle<> awaitingCoroutine) noexcept;

void await_resume() noexcept {}

private:

friend class static_thread_pool;

static_thread_pool* m_threadPool;

cppcoro::coroutine_handle<> m_awaitingCoroutine;

schedule_operation* m_next;

};

std::uint32_t thread_count() const noexcept { return m_threadCount; }

[[nodiscard]]

schedule_operation schedule() noexcept { return schedule_operation{ this }; }

private:

friend class schedule_operation;

void run_worker_thread(std::uint32_t threadIndex) noexcept;

void shutdown();

void schedule_impl(schedule_operation* operation) noexcept;

void remote_enqueue(schedule_operation* operation) noexcept;

bool has_any_queued_work_for(std::uint32_t threadIndex) noexcept;

bool approx_has_any_queued_work_for(std::uint32_t threadIndex) const noexcept;

bool is_shutdown_requested() const noexcept;

void notify_intent_to_sleep(std::uint32_t threadIndex) noexcept;

void try_clear_intent_to_sleep(std::uint32_t threadIndex) noexcept;

schedule_operation* try_global_dequeue() noexcept;

/// Try to steal a task from another thread.

///

/// \return

/// A pointer to the operation that was stolen if one could be stolen

/// from another thread. Otherwise returns nullptr if none of the other

/// threads had any tasks that could be stolen.

schedule_operation* try_steal_from_other_thread(std::uint32_t thisThreadIndex) noexcept;

void wake_one_thread() noexcept;

class thread_state;

static thread_local thread_state* s_currentState;

static thread_local static_thread_pool* s_currentThreadPool;

const std::uint32_t m_threadCount;

const std::unique_ptr<thread_state[]> m_threadStates;

std::vector<std::thread> m_threads;

std::atomic<bool> m_stopRequested;

std::mutex m_globalQueueMutex;

std::atomic<schedule_operation*> m_globalQueueHead;

//alignas(std::hardware_destructive_interference_size)

std::atomic<schedule_operation*> m_globalQueueTail;

//alignas(std::hardware_destructive_interference_size)

std::atomic<std::uint32_t> m_sleepingThreadCount;