thread_pool.hpp

#pragma once
 
#include "expected.hpp"
#include "scheduler_policy.hpp"
#include "thread_wrapper.hpp"
#include <algorithm>
#include <array>
#include <atomic>
#include <condition_variable>
#include <future>
#include <mutex>
#include <queue>
#include <random>
#include <vector>
 
namespace threadschedule
{

template <typename T>
class WorkStealingDeque
{
  public:
    static constexpr size_t CACHE_LINE_SIZE = 64;
    static constexpr size_t DEFAULT_CAPACITY = 1024;
 
  private:
    struct alignas(CACHE_LINE_SIZE) AlignedItem
    {
        T item;
        AlignedItem() = default;
        AlignedItem(T&& t) : item(std::move(t))
        {
        }
        AlignedItem(T const& t) : item(t)
        {
        }
    };
 
    std::unique_ptr<AlignedItem[]> buffer_;
    size_t capacity_;
 
    alignas(CACHE_LINE_SIZE) std::atomic<size_t> top_{0};    // Owner pushes/pops here
    alignas(CACHE_LINE_SIZE) std::atomic<size_t> bottom_{0}; // Thieves steal here
    alignas(CACHE_LINE_SIZE) mutable std::mutex mutex_;      // For synchronization
 
  public:
    explicit WorkStealingDeque(size_t capacity = DEFAULT_CAPACITY)
        : buffer_(std::make_unique<AlignedItem[]>(capacity)), capacity_(capacity)
    {
    }
 
    // Thread-safe operations
    [[nodiscard]] auto push(T&& item) -> bool
    {
        std::lock_guard<std::mutex> lock(mutex_);
        size_t const t = top_.load(std::memory_order_relaxed);
        size_t const b = bottom_.load(std::memory_order_relaxed);
 
        if (t - b >= capacity_)
        {
            return false; // Queue full
        }
 
        buffer_[t % capacity_] = AlignedItem(std::move(item));
        top_.store(t + 1, std::memory_order_release);
        return true;
    }
 
    [[nodiscard]] auto push(T const& item) -> bool
    {
        std::lock_guard<std::mutex> lock(mutex_);
        size_t const t = top_.load(std::memory_order_relaxed);
        size_t const b = bottom_.load(std::memory_order_relaxed);
 
        if (t - b >= capacity_)
        {
            return false; // Queue full
        }
 
        buffer_[t % capacity_] = AlignedItem(item);
        top_.store(t + 1, std::memory_order_release);
        return true;
    }
 
    [[nodiscard]] auto pop(T& item) -> bool
    {
        std::lock_guard<std::mutex> lock(mutex_);
        size_t const t = top_.load(std::memory_order_relaxed);
        size_t const b = bottom_.load(std::memory_order_relaxed);
 
        if (t <= b)
        {
            return false; // Empty
        }
 
        size_t const new_top = t - 1;
        item = std::move(buffer_[new_top % capacity_].item);
        top_.store(new_top, std::memory_order_relaxed);
        return true;
    }
 
    // Thief operations (other threads stealing work)
    [[nodiscard]] auto steal(T& item) -> bool
    {
        std::lock_guard<std::mutex> lock(mutex_);
        size_t const b = bottom_.load(std::memory_order_relaxed);
        size_t const t = top_.load(std::memory_order_relaxed);
 
        if (b >= t)
        {
            return false; // Empty
        }
 
        item = std::move(buffer_[b % capacity_].item);
        bottom_.store(b + 1, std::memory_order_relaxed);
        return true;
    }
 
    [[nodiscard]] auto size() const -> size_t
    {
        size_t const t = top_.load(std::memory_order_relaxed);
        size_t const b = bottom_.load(std::memory_order_relaxed);
        return t > b ? t - b : 0;
    }
 
    [[nodiscard]] auto empty() const -> bool
    {
        return size() == 0;
    }
};

class HighPerformancePool
{
  public:
    using Task = std::function<void()>;
 
    struct Statistics
    {
        size_t total_threads;
        size_t active_threads;
        size_t pending_tasks;
        size_t completed_tasks;
        size_t stolen_tasks;
        double tasks_per_second;
        std::chrono::microseconds avg_task_time;
    };
 
    explicit HighPerformancePool(size_t num_threads = std::thread::hardware_concurrency())
        : num_threads_(num_threads == 0 ? 1 : num_threads), stop_(false), next_victim_(0),
          start_time_(std::chrono::steady_clock::now())
    {
        // Initialize per-thread work queues
        worker_queues_.resize(num_threads_);
        for (size_t i = 0; i < num_threads_; ++i)
        {
            worker_queues_[i] = std::make_unique<WorkStealingDeque<Task>>();
        }
 
        workers_.reserve(num_threads_);
 
        // Create worker threads with thread-local storage
        for (size_t i = 0; i < num_threads_; ++i)
        {
            workers_.emplace_back(&HighPerformancePool::worker_function, this, i);
        }
    }
 
    HighPerformancePool(HighPerformancePool const&) = delete;
    auto operator=(HighPerformancePool const&) -> HighPerformancePool& = delete;
 
    ~HighPerformancePool()
    {
        shutdown();
    }

    template <typename F, typename... Args>
    auto submit(F&& f, Args&&... args) -> std::future<std::invoke_result_t<F, Args...>>
    {
        using return_type = std::invoke_result_t<F, Args...>;
 
        auto task = std::make_shared<std::packaged_task<return_type()>>(
            std::bind(std::forward<F>(f), std::forward<Args>(args)...));
 
        std::future<return_type> result = task->get_future();
 
        if (stop_.load(std::memory_order_acquire))
        {
            throw std::runtime_error("ThreadPool is shutting down");
        }
 
        // Try to submit to least loaded queue (round-robin with fallback)
        size_t const preferred_queue = next_victim_.fetch_add(1, std::memory_order_relaxed) % num_threads_;
 
        // First try the preferred queue
        if (worker_queues_[preferred_queue]->push([task]() { (*task)(); }))
        {
            wakeup_condition_.notify_one();
            return result;
        }
 
        // If preferred queue is full, try a few random ones
        for (size_t attempts = 0; attempts < (std::min)(num_threads_, size_t(3)); ++attempts)
        {
            size_t const idx = (preferred_queue + attempts + 1) % num_threads_;
            if (worker_queues_[idx]->push([task]() { (*task)(); }))
            {
                wakeup_condition_.notify_one();
                return result;
            }
        }
 
        // All local queues full, use overflow queue
        {
            std::lock_guard<std::mutex> lock(overflow_mutex_);
            if (stop_.load(std::memory_order_relaxed))
            {
                throw std::runtime_error("ThreadPool is shutting down");
            }
            overflow_tasks_.emplace([task]() { (*task)(); });
        }
 
        wakeup_condition_.notify_all();
        return result;
    }

    template <typename Iterator>
    auto submit_batch(Iterator begin, Iterator end) -> std::vector<std::future<void>>
    {
        std::vector<std::future<void>> futures;
        size_t const batch_size = std::distance(begin, end);
        futures.reserve(batch_size);
 
        if (stop_.load(std::memory_order_acquire))
        {
            throw std::runtime_error("ThreadPool is shutting down");
        }
 
        // Distribute batch across worker queues
        size_t queue_idx = next_victim_.fetch_add(batch_size, std::memory_order_relaxed) % num_threads_;
 
        for (auto it = begin; it != end; ++it)
        {
            auto task = std::make_shared<std::packaged_task<void()>>(*it);
            futures.push_back(task->get_future());
 
            // Try to place in worker queue, round-robin style
            bool queued = false;
            for (size_t attempts = 0; attempts < num_threads_; ++attempts)
            {
                if (worker_queues_[queue_idx]->push([task]() { (*task)(); }))
                {
                    queued = true;
                    break;
                }
                queue_idx = (queue_idx + 1) % num_threads_;
            }
 
            if (!queued)
            {
                // Overflow to global queue
                std::lock_guard<std::mutex> lock(overflow_mutex_);
                overflow_tasks_.emplace([task]() { (*task)(); });
            }
        }
 
        // Wake up workers for the batch
        wakeup_condition_.notify_all();
        return futures;
    }

    template <typename Iterator, typename F>
    void parallel_for_each(Iterator begin, Iterator end, F&& func)
    {
        size_t const total_items = std::distance(begin, end);
        if (total_items == 0)
            return;
 
        // Calculate optimal chunk size for cache efficiency
        size_t const chunk_size = (std::max)(size_t(1), total_items / (num_threads_ * 4));
        std::vector<std::future<void>> futures;
 
        for (auto it = begin; it < end;)
        {
            auto chunk_end = (std::min)(it + chunk_size, end);
 
            futures.push_back(submit([func, it, chunk_end]() {
                for (auto chunk_it = it; chunk_it != chunk_end; ++chunk_it)
                {
                    func(*chunk_it);
                }
            }));
 
            it = chunk_end;
        }
 
        // Wait for all chunks to complete
        for (auto& future : futures)
        {
            future.wait();
        }
    }
 
    [[nodiscard]] auto size() const noexcept -> size_t
    {
        return num_threads_;
    }
 
    [[nodiscard]] auto pending_tasks() const -> size_t
    {
        size_t total = 0;
        for (auto const& queue : worker_queues_)
        {
            total += queue->size();
        }
 
        std::lock_guard<std::mutex> lock(overflow_mutex_);
        total += overflow_tasks_.size();
        return total;
    }

    auto configure_threads(std::string const& name_prefix, SchedulingPolicy policy = SchedulingPolicy::OTHER,
                           ThreadPriority priority = ThreadPriority::normal()) -> expected<void, std::error_code>
    {
        bool success = true;
 
        for (size_t i = 0; i < workers_.size(); ++i)
        {
            std::string const thread_name = name_prefix + "_" + std::to_string(i);
 
            if (!workers_[i].set_name(thread_name).has_value())
            {
                success = false;
            }
 
            if (!workers_[i].set_scheduling_policy(policy, priority).has_value())
            {
                success = false;
            }
        }
        if (success)
            return {};
        return unexpected(std::make_error_code(std::errc::operation_not_permitted));
    }
 
    auto set_affinity(ThreadAffinity const& affinity) -> expected<void, std::error_code>
    {
        bool success = true;
 
        for (auto& worker : workers_)
        {
            if (!worker.set_affinity(affinity).has_value())
            {
                success = false;
            }
        }
        if (success)
            return {};
        return unexpected(std::make_error_code(std::errc::operation_not_permitted));
    }
 
    auto distribute_across_cpus() -> expected<void, std::error_code>
    {
        auto const cpu_count = std::thread::hardware_concurrency();
        if (cpu_count == 0)
            return unexpected(std::make_error_code(std::errc::invalid_argument));
 
        bool success = true;
 
        for (size_t i = 0; i < workers_.size(); ++i)
        {
            ThreadAffinity affinity({static_cast<int>(i % cpu_count)});
            if (!workers_[i].set_affinity(affinity).has_value())
            {
                success = false;
            }
        }
        if (success)
            return {};
        return unexpected(std::make_error_code(std::errc::operation_not_permitted));
    }
 
    void wait_for_tasks()
    {
        std::unique_lock<std::mutex> lock(completion_mutex_);
        completion_condition_.wait(
            lock, [this] { return pending_tasks() == 0 && active_tasks_.load(std::memory_order_acquire) == 0; });
    }
 
    void shutdown()
    {
        {
            std::lock_guard<std::mutex> lock(overflow_mutex_);
            if (stop_.exchange(true, std::memory_order_acq_rel))
            {
                return; // Already shutting down
            }
        }
 
        wakeup_condition_.notify_all();
 
        for (auto& worker : workers_)
        {
            if (worker.joinable())
            {
                worker.join();
            }
        }
 
        workers_.clear();
    }

    auto get_statistics() const -> Statistics
    {
        auto const now = std::chrono::steady_clock::now();
        auto const elapsed = std::chrono::duration_cast<std::chrono::seconds>(now - start_time_);
 
        Statistics stats;
        stats.total_threads = num_threads_;
        stats.active_threads = active_tasks_.load(std::memory_order_acquire);
        stats.pending_tasks = pending_tasks();
        stats.completed_tasks = completed_tasks_.load(std::memory_order_acquire);
        stats.stolen_tasks = stolen_tasks_.load(std::memory_order_acquire);
 
        if (elapsed.count() > 0)
        {
            stats.tasks_per_second = static_cast<double>(stats.completed_tasks) / elapsed.count();
        }
        else
        {
            stats.tasks_per_second = 0.0;
        }
 
        auto const total_task_time = total_task_time_.load(std::memory_order_acquire);
        if (stats.completed_tasks > 0)
        {
            stats.avg_task_time = std::chrono::microseconds(total_task_time / stats.completed_tasks);
        }
        else
        {
            stats.avg_task_time = std::chrono::microseconds(0);
        }
 
        return stats;
    }
 
  private:
    size_t num_threads_;
    std::vector<ThreadWrapper> workers_;
    std::vector<std::unique_ptr<WorkStealingDeque<Task>>> worker_queues_;
 
    // Overflow queue for when worker queues are full
    std::queue<Task> overflow_tasks_;
    mutable std::mutex overflow_mutex_;
 
    // Synchronization
    std::atomic<bool> stop_;
    std::condition_variable wakeup_condition_;
    std::mutex wakeup_mutex_;
 
    std::condition_variable completion_condition_;
    std::mutex completion_mutex_;
 
    // Load balancing and statistics
    std::atomic<size_t> next_victim_;
    std::atomic<size_t> active_tasks_{0};
    std::atomic<size_t> completed_tasks_{0};
    std::atomic<size_t> stolen_tasks_{0};
    std::atomic<uint64_t> total_task_time_{0}; // microseconds
 
    std::chrono::steady_clock::time_point start_time_;
 
    // NOLINTNEXTLINE(readability-function-cognitive-complexity)
    void worker_function(size_t worker_id)
    {
        // Thread-local random number generator for work stealing
        thread_local std::mt19937 gen = []() {
            std::random_device device;
            return std::mt19937(device());
        }();
 
        Task task;
        std::uniform_int_distribution<size_t> dist(0, num_threads_ - 1);
 
        while (true)
        {
            bool found_task = false;
 
            // 1. Try to get task from own queue (fast path)
            if (worker_queues_[worker_id]->pop(task))
            {
                found_task = true;
            }
            // 2. Try to steal from other workers (limit attempts to reduce contention)
            else
            {
                size_t const max_steal_attempts = (std::min)(num_threads_, size_t(4));
                for (size_t attempts = 0; attempts < max_steal_attempts; ++attempts)
                {
                    size_t const victim_id = dist(gen);
                    if (victim_id != worker_id && worker_queues_[victim_id]->steal(task))
                    {
                        found_task = true;
                        stolen_tasks_.fetch_add(1, std::memory_order_relaxed);
                        break;
                    }
                }
            }
 
            // 3. Try overflow queue
            if (!found_task)
            {
                std::lock_guard<std::mutex> lock(overflow_mutex_);
                if (!overflow_tasks_.empty())
                {
                    task = std::move(overflow_tasks_.front());
                    overflow_tasks_.pop();
                    found_task = true;
                }
            }
 
            if (found_task)
            {
                // Execute task with timing
                active_tasks_.fetch_add(1, std::memory_order_relaxed);
 
                auto const start_time = std::chrono::steady_clock::now();
                try
                {
                    task();
                }
                catch (...)
                {
                    // Log exception or handle as needed
                }
                auto const end_time = std::chrono::steady_clock::now();
 
                auto const task_duration = std::chrono::duration_cast<std::chrono::microseconds>(end_time - start_time);
                total_task_time_.fetch_add(task_duration.count(), std::memory_order_relaxed);
 
                active_tasks_.fetch_sub(1, std::memory_order_relaxed);
                completed_tasks_.fetch_add(1, std::memory_order_relaxed);
 
                completion_condition_.notify_all();
            }
            else
            {
                // No work found, check if we should stop
                if (stop_.load(std::memory_order_acquire))
                {
                    break;
                }
 
                // Wait for work with adaptive timeout
                std::unique_lock<std::mutex> lock(wakeup_mutex_);
                wakeup_condition_.wait_for(lock, std::chrono::microseconds(100));
            }
        }
    }
};

class FastThreadPool
{
  public:
    using Task = std::function<void()>;
 
    struct Statistics
    {
        size_t total_threads;
        size_t active_threads;
        size_t pending_tasks;
        size_t completed_tasks;
        double tasks_per_second;
        std::chrono::microseconds avg_task_time;
    };
 
    explicit FastThreadPool(size_t num_threads = std::thread::hardware_concurrency())
        : num_threads_(num_threads == 0 ? 1 : num_threads), stop_(false), start_time_(std::chrono::steady_clock::now())
    {
        workers_.reserve(num_threads_);
 
        // Create worker threads
        for (size_t i = 0; i < num_threads_; ++i)
        {
            workers_.emplace_back(&FastThreadPool::worker_function, this, i);
        }
    }
 
    FastThreadPool(FastThreadPool const&) = delete;
    auto operator=(FastThreadPool const&) -> FastThreadPool& = delete;
 
    ~FastThreadPool()
    {
        shutdown();
    }

    template <typename F, typename... Args>
    auto submit(F&& f, Args&&... args) -> std::future<std::invoke_result_t<F, Args...>>
    {
        using return_type = std::invoke_result_t<F, Args...>;
 
        auto task = std::make_shared<std::packaged_task<return_type()>>(
            std::bind(std::forward<F>(f), std::forward<Args>(args)...));
 
        std::future<return_type> result = task->get_future();
 
        {
            std::lock_guard<std::mutex> lock(queue_mutex_);
            if (stop_)
            {
                throw std::runtime_error("FastThreadPool is shutting down");
            }
            tasks_.emplace([task]() { (*task)(); });
        }
 
        condition_.notify_one();
        return result;
    }

    template <typename Iterator>
    auto submit_batch(Iterator begin, Iterator end) -> std::vector<std::future<void>>
    {
        std::vector<std::future<void>> futures;
        size_t const batch_size = std::distance(begin, end);
        futures.reserve(batch_size);
 
        {
            std::lock_guard<std::mutex> lock(queue_mutex_);
            if (stop_)
            {
                throw std::runtime_error("FastThreadPool is shutting down");
            }
 
            for (auto it = begin; it != end; ++it)
            {
                auto task = std::make_shared<std::packaged_task<void()>>(*it);
                futures.push_back(task->get_future());
                tasks_.emplace([task]() { (*task)(); });
            }
        }
 
        // Wake up all workers for batch processing
        condition_.notify_all();
        return futures;
    }
 
    void shutdown()
    {
        {
            std::lock_guard<std::mutex> lock(queue_mutex_);
            if (stop_)
                return;
            stop_ = true;
        }
 
        condition_.notify_all();
 
        for (auto& worker : workers_)
        {
            if (worker.joinable())
            {
                worker.join();
            }
        }
 
        workers_.clear();
    }
 
    auto configure_threads(std::string const& name_prefix, SchedulingPolicy policy = SchedulingPolicy::OTHER,
                           ThreadPriority priority = ThreadPriority::normal()) -> bool
    {
        bool success = true;
 
        for (size_t i = 0; i < workers_.size(); ++i)
        {
            std::string const thread_name = name_prefix + "_" + std::to_string(i);
 
            if (!workers_[i].set_name(thread_name))
            {
                success = false;
            }
 
            if (!workers_[i].set_scheduling_policy(policy, priority))
            {
                success = false;
            }
        }
 
        return success;
    }
 
    auto set_affinity(ThreadAffinity const& affinity) -> bool
    {
        bool success = true;
 
        for (auto& worker : workers_)
        {
            if (!worker.set_affinity(affinity))
            {
                success = false;
            }
        }
 
        return success;
    }
 
    auto distribute_across_cpus() -> bool
    {
        auto const cpu_count = std::thread::hardware_concurrency();
        if (cpu_count == 0)
            return false;
 
        bool success = true;
 
        for (size_t i = 0; i < workers_.size(); ++i)
        {
            ThreadAffinity affinity({static_cast<int>(i % cpu_count)});
            if (!workers_[i].set_affinity(affinity))
            {
                success = false;
            }
        }
 
        return success;
    }
 
    [[nodiscard]] auto size() const noexcept -> size_t
    {
        return num_threads_;
    }
 
    [[nodiscard]] auto pending_tasks() const -> size_t
    {
        std::lock_guard<std::mutex> lock(queue_mutex_);
        return tasks_.size();
    }
 
    void wait_for_tasks()
    {
        std::unique_lock<std::mutex> lock(queue_mutex_);
        task_finished_condition_.wait(
            lock, [this] { return tasks_.empty() && active_tasks_.load(std::memory_order_acquire) == 0; });
    }
 
    [[nodiscard]] auto get_statistics() const -> Statistics
    {
        auto const now = std::chrono::steady_clock::now();
        auto const elapsed = std::chrono::duration_cast<std::chrono::seconds>(now - start_time_);
 
        std::lock_guard<std::mutex> lock(queue_mutex_);
        Statistics stats;
        stats.total_threads = num_threads_;
        stats.active_threads = active_tasks_.load(std::memory_order_acquire);
        stats.pending_tasks = tasks_.size();
        stats.completed_tasks = completed_tasks_.load(std::memory_order_acquire);
 
        if (elapsed.count() > 0)
        {
            stats.tasks_per_second = static_cast<double>(stats.completed_tasks) / elapsed.count();
        }
        else
        {
            stats.tasks_per_second = 0.0;
        }
 
        auto const total_task_time = total_task_time_.load(std::memory_order_acquire);
        if (stats.completed_tasks > 0)
        {
            stats.avg_task_time = std::chrono::microseconds(total_task_time / stats.completed_tasks);
        }
        else
        {
            stats.avg_task_time = std::chrono::microseconds(0);
        }
 
        return stats;
    }
 
  private:
    size_t num_threads_;
    std::vector<ThreadWrapper> workers_;
    std::queue<Task> tasks_;
 
    mutable std::mutex queue_mutex_;
    std::condition_variable condition_;
    std::condition_variable task_finished_condition_;
    std::atomic<bool> stop_;
    std::atomic<size_t> active_tasks_{0};
    std::atomic<size_t> completed_tasks_{0};
    std::atomic<uint64_t> total_task_time_{0}; // microseconds
 
    std::chrono::steady_clock::time_point start_time_;
 
    void worker_function(size_t /* worker_id */)
    {
        while (true)
        {
            Task task;
            bool found_task = false;
 
            {
                std::unique_lock<std::mutex> lock(queue_mutex_);
 
                if (condition_.wait_for(lock, std::chrono::milliseconds(10),
                                        [this] { return stop_ || !tasks_.empty(); }))
                {
                    if (stop_ && tasks_.empty())
                    {
                        return;
                    }
 
                    if (!tasks_.empty())
                    {
                        task = std::move(tasks_.front());
                        tasks_.pop();
                        found_task = true;
                        active_tasks_.fetch_add(1, std::memory_order_relaxed);
                    }
                }
                else if (stop_)
                {
                    return;
                }
            }
 
            if (found_task)
            {
                auto const start_time = std::chrono::steady_clock::now();
                try
                {
                    task();
                }
                catch (...)
                {
                }
                auto const end_time = std::chrono::steady_clock::now();
 
                auto const task_duration = std::chrono::duration_cast<std::chrono::microseconds>(end_time - start_time);
                total_task_time_.fetch_add(task_duration.count(), std::memory_order_relaxed);
 
                active_tasks_.fetch_sub(1, std::memory_order_relaxed);
                completed_tasks_.fetch_add(1, std::memory_order_relaxed);
 
                task_finished_condition_.notify_all();
            }
        }
    }
};

class ThreadPool
{
  public:
    using Task = std::function<void()>;
 
    struct Statistics
    {
        size_t total_threads;
        size_t active_threads;
        size_t pending_tasks;
        size_t completed_tasks;
    };
 
    explicit ThreadPool(size_t num_threads = std::thread::hardware_concurrency())
        : num_threads_(num_threads == 0 ? 1 : num_threads), stop_(false)
    {
        workers_.reserve(num_threads_);
 
        // Create worker threads
        for (size_t i = 0; i < num_threads_; ++i)
        {
            workers_.emplace_back(&ThreadPool::worker_function, this);
        }
    }
 
    ThreadPool(ThreadPool const&) = delete;
    auto operator=(ThreadPool const&) -> ThreadPool& = delete;
 
    ~ThreadPool()
    {
        shutdown();
    }

    template <typename F, typename... Args>
    auto submit(F&& f, Args&&... args) -> std::future<std::invoke_result_t<F, Args...>>
    {
        using return_type = std::invoke_result_t<F, Args...>;
 
        auto task = std::make_shared<std::packaged_task<return_type()>>(
            std::bind(std::forward<F>(f), std::forward<Args>(args)...));
 
        std::future<return_type> result = task->get_future();
 
        {
            std::lock_guard<std::mutex> lock(queue_mutex_);
 
            if (stop_)
            {
                throw std::runtime_error("ThreadPool is shutting down");
            }
 
            tasks_.emplace([task]() { (*task)(); });
        }
 
        condition_.notify_one();
        return result;
    }

    template <typename Iterator>
    auto submit_range(Iterator begin, Iterator end) -> std::vector<std::future<void>>
    {
        std::vector<std::future<void>> futures;
        futures.reserve(std::distance(begin, end));
 
        for (auto it = begin; it != end; ++it)
        {
            futures.push_back(submit(*it));
        }
 
        return futures;
    }

    template <typename Iterator, typename F>
    void parallel_for_each(Iterator begin, Iterator end, F&& func)
    {
        std::vector<std::future<void>> futures;
        futures.reserve(std::distance(begin, end));
 
        for (auto it = begin; it != end; ++it)
        {
            futures.push_back(submit([func, it]() { func(*it); }));
        }
 
        // Wait for all tasks to complete
        for (auto& future : futures)
        {
            future.wait();
        }
    }
 
    [[nodiscard]] auto size() const noexcept -> size_t
    {
        return num_threads_;
    }
 
    [[nodiscard]] auto pending_tasks() const -> size_t
    {
        std::lock_guard<std::mutex> lock(queue_mutex_);
        return tasks_.size();
    }

    auto configure_threads(std::string const& name_prefix, SchedulingPolicy policy = SchedulingPolicy::OTHER,
                           ThreadPriority priority = ThreadPriority::normal()) -> bool
    {
        bool success = true;
 
        for (size_t i = 0; i < workers_.size(); ++i)
        {
            std::string const thread_name = name_prefix + "_" + std::to_string(i);
 
            if (!workers_[i].set_name(thread_name))
            {
                success = false;
            }
 
            if (!workers_[i].set_scheduling_policy(policy, priority))
            {
                success = false;
            }
        }
 
        return success;
    }
 
    auto set_affinity(ThreadAffinity const& affinity) -> bool
    {
        bool success = true;
 
        for (auto& worker : workers_)
        {
            if (!worker.set_affinity(affinity))
            {
                success = false;
            }
        }
 
        return success;
    }
 
    auto distribute_across_cpus() -> bool
    {
        auto const cpu_count = std::thread::hardware_concurrency();
        if (cpu_count == 0)
            return false;
 
        bool success = true;
 
        for (size_t i = 0; i < workers_.size(); ++i)
        {
            ThreadAffinity affinity({static_cast<int>(i % cpu_count)});
            if (!workers_[i].set_affinity(affinity))
            {
                success = false;
            }
        }
 
        return success;
    }
 
    void wait_for_tasks()
    {
        std::unique_lock<std::mutex> lock(queue_mutex_);
        task_finished_condition_.wait(lock, [this] { return tasks_.empty() && active_tasks_ == 0; });
    }
 
    void shutdown()
    {
        {
            std::lock_guard<std::mutex> lock(queue_mutex_);
            if (stop_)
                return;
            stop_ = true;
        }
 
        condition_.notify_all();
 
        for (auto& worker : workers_)
        {
            if (worker.joinable())
            {
                worker.join();
            }
        }
 
        workers_.clear();
    }
 
    [[nodiscard]] auto get_statistics() const -> Statistics
    {
        std::lock_guard<std::mutex> lock(queue_mutex_);
        Statistics stats;
        stats.total_threads = num_threads_;
        stats.active_threads = active_tasks_;
        stats.pending_tasks = tasks_.size();
        stats.completed_tasks = completed_tasks_;
        return stats;
    }
 
  private:
    size_t num_threads_;
    std::vector<ThreadWrapper> workers_;
    std::queue<Task> tasks_;
 
    mutable std::mutex queue_mutex_;
    std::condition_variable condition_;
    std::condition_variable task_finished_condition_;
    std::atomic<bool> stop_;
    std::atomic<size_t> active_tasks_{0};
    std::atomic<size_t> completed_tasks_{0};
 
    void worker_function()
    {
        while (true)
        {
            Task task;
 
            {
                std::unique_lock<std::mutex> lock(queue_mutex_);
 
                condition_.wait(lock, [this] { return stop_ || !tasks_.empty(); });
 
                if (stop_ && tasks_.empty())
                {
                    return;
                }
 
                task = std::move(tasks_.front());
                tasks_.pop();
                ++active_tasks_;
            }
 
            try
            {
                task();
            }
            catch (...)
            {
                // Log exception or handle as needed
            }
 
            {
                std::lock_guard<std::mutex> lock(queue_mutex_);
                --active_tasks_;
                ++completed_tasks_;
            }
 
            task_finished_condition_.notify_all();
        }
    }
};

class GlobalThreadPool
{
  public:
    static auto instance() -> ThreadPool&
    {
        static ThreadPool pool(std::thread::hardware_concurrency());
        return pool;
    }
 
    template <typename F, typename... Args>
    static auto submit(F&& f, Args&&... args)
    {
        return instance().submit(std::forward<F>(f), std::forward<Args>(args)...);
    }
 
    template <typename Iterator>
    static auto submit_range(Iterator begin, Iterator end)
    {
        return instance().submit_range(begin, end);
    }
 
    template <typename Iterator, typename F>
    static void parallel_for_each(Iterator begin, Iterator end, F&& func)
    {
        instance().parallel_for_each(begin, end, std::forward<F>(func));
    }
 
  private:
    GlobalThreadPool() = default;
};

class GlobalHighPerformancePool
{
  public:
    static auto instance() -> HighPerformancePool&
    {
        static HighPerformancePool pool(std::thread::hardware_concurrency());
        return pool;
    }
 
    template <typename F, typename... Args>
    static auto submit(F&& f, Args&&... args)
    {
        return instance().submit(std::forward<F>(f), std::forward<Args>(args)...);
    }
 
    template <typename Iterator>
    static auto submit_batch(Iterator begin, Iterator end)
    {
        return instance().submit_batch(begin, end);
    }
 
    template <typename Iterator, typename F>
    static void parallel_for_each(Iterator begin, Iterator end, F&& func)
    {
        instance().parallel_for_each(begin, end, std::forward<F>(func));
    }
 
  private:
    GlobalHighPerformancePool() = default;
};

template <typename Container, typename F>
void parallel_for_each(Container& container, F&& func)
{
    GlobalThreadPool::parallel_for_each(container.begin(), container.end(), std::forward<F>(func));
}
 
} // namespace threadschedule