Start
  thread_split_1
    ThreadStart
      task_f1
        task_f2
      task_g1
        task_g2
          join
    ThreadStart
      task_f1
        task_f2
      task_g1
        task_g2
          join
    ThreadStart
      task_f1
        task_f2
      task_g1
        task_g2
          join
            thread_merge_1
              last
                End