ThreadPool.h

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#ifndef THREAD_POOL_H
#define THREAD_POOL_H
 
#include "CNum/DataStructs/ConcurrentQueue.h"
#include "CNum/DataStructs/Memory/Arena.h"
 
#include <functional>
#include <vector>
#include <thread>
#include <mutex>
#include <future>
#include <atomic>
#include <atomic>

namespace CNum::Multithreading {
  using Func = std::function< void(arena_t *) >;

  constexpr size_t default_arena_init_block_ct = 16500;

  struct ThreadPoolConfig {
    size_t arena_blocks_to_allocate;
  };

  class ThreadPool {
  private:
    ::CNum::DataStructs::ConcurrentQueue< Func > _q;
    int _num_threads;
    std::vector<std::thread> _threads;
    std::mutex _mtx;
    ::std::atomic<bool> _is_shutdown;
    static thread_local int _worker_id;

    void worker(ThreadPoolConfig config, int worker_id);

    ThreadPool(ThreadPoolConfig config);
  
 
  public:
    static ThreadPool *get_thread_pool(ThreadPoolConfig config = { default_arena_init_block_ct });

    static int get_worker_id();

    ~ThreadPool();
  
    ThreadPool(const ThreadPool &other) = delete;
    ThreadPool &operator=(const ThreadPool &other) = delete;
    ThreadPool(ThreadPool &&other) = delete;
    ThreadPool &operator=(ThreadPool &&other) = delete;

    void shutdown();
    
    template<typename T>
    std::future<T> submit(std::function< T(arena_t *arena) > f) {
      if (_is_shutdown.load(::std::memory_order_acquire))
    throw ::std::runtime_error("Thread pool submit error - Submit cannot be called after thread pool is shut down");
      
      auto p = std::make_shared< std::promise<T> >();
      std::future<T> fut = p->get_future();
  
      auto func = [p, f] (arena_t *arena) mutable {
    if constexpr (std::is_void_v<T>) {
      f(arena);
      p->set_value();
    } else {
      p->set_value(f(arena));
    }
      };
  
      _q.enqueue(func);
      return fut;
    }
  };
};
 
#endif