added leader follower thread pool

include/matador/utils/leader_follower_thread_pool.hpp

@@ -0,0 +1,125 @@
+#ifndef LEADER_FOLLOWER_THREAD_POOL_HPP
+#define LEADER_FOLLOWER_THREAD_POOL_HPP
+
+#include <memory>
+#include <thread>
+#include <vector>
+#include <functional>
+#include <deque>
+#include <atomic>
+#include <mutex>
+#include <condition_variable>
+
+namespace matador::utils {
+
+/**
+ * This thread pool class implements the
+ * leader follower pattern.
+ */
+class leader_follower_thread_pool
+{
+private:
+  leader_follower_thread_pool(const leader_follower_thread_pool &);
+
+  leader_follower_thread_pool &operator=(const leader_follower_thread_pool &);
+
+public:
+  /**
+   * Creates a new leader follower thread pool instance
+   * with the given thread pool size and given join
+   * function.
+   *
+   * @tparam F Type of join function
+   * @param size Number of threads
+   * @param join_func Join function.
+   */
+  template<typename F>
+  leader_follower_thread_pool(std::size_t size, F join_func)
+    : num_threads_(size), join_(join_func)
+    , follower_(size) {}
+
+  ~leader_follower_thread_pool();
+
+  /**
+   * Starts the thread pool.
+   */
+  void start();
+
+  /**
+   * Stops the thread pool.
+   */
+  void stop();
+
+  /**
+   * Promotes the next new leading thread.
+   */
+  void promote_new_leader();
+
+  /**
+   * Returns number of threads.
+   *
+   * @return Number of threads.
+   */
+  std::size_t size() const;
+
+  /**
+   * Shuts the thread pool down.
+   */
+  void shutdown();
+
+  /**
+   * Returns the thread id of the current
+   * leading thread.
+   *
+   * @return Thread id of the leading thread.
+   */
+  std::thread::id leader();
+
+  /**
+   * Returns the current number of
+   * thread followers.
+   *
+   * @return Number of follower threads.
+   */
+  std::size_t num_follower() const;
+
+  /**
+   * Returns true if the thread pool is running.
+   *
+   * @return True if thread pool is running.
+   */
+  bool is_running() const;
+
+private:
+  /*
+   * wait for a task to execute
+   */
+  void execute();
+
+private:
+  typedef std::vector<std::thread> thread_vector_t;
+  typedef std::function<void()> join_func_t;
+
+  std::size_t num_threads_{};
+
+  std::thread::id leader_{};
+  std::thread::id null_id{};
+
+  join_func_t join_;
+  thread_vector_t threads_;
+
+  std::mutex mutex_;
+  std::condition_variable condition_task_;
+  std::condition_variable condition_synchronizer_;
+
+  std::atomic_bool signal_ready_ { false };
+  std::atomic_bool signal_shutdown_ { false };
+
+  std::atomic_bool is_running_ { false };
+
+  std::atomic_size_t follower_{};
+};
+
+}
+
+#endif //LEADER_FOLLOWER_THREAD_POOL_HPP