code: public static <T extends H2OCountedCompleter> T submitTask( T task ) {
      int priority = task.priority();
      if( priority < LOW_PRIORITY_API_WORK )
        LOW_PRIORITY_API_WORK_CLASS = task.getClass().toString();
      assert MIN_PRIORITY <= priority && priority <= MAX_PRIORITY:"priority " + priority + " is out of range, expected range is < " + MIN_PRIORITY + "," + MAX_PRIORITY + ">";
      if( FJPS[priority]==null )
        synchronized( H2O.class ) { if( FJPS[priority] == null ) FJPS[priority] = new PrioritizedForkJoinPool(priority,-1); }
      FJPS[priority].submit(task);
      return task;
    }
docs: Submit to the correct priority queue