Method wait

src/include/zvec/ailego/parallel/thread_pool.h:293–296

Wait until task finished

    //! Wait until task finished
    void wait(void) {
      std::unique_lock<std::mutex> lock(mutex_);
      cond_.wait(lock, [this]() { return finished_.load(); });
    }

   private:
    std::atomic_bool finished_{false};