assert Thread.holdsLock(this);
  private TaskScoreTable updateTST() {    if (_tst == null) {      int n = subtasks.size();      if (n == 0) return null;      Task[] _tasks = (Task[]) subtasks.toArray(new Task[n]);      _tst = new TaskScoreTable(_tasks);    }    for (int i = 0, n = _tst.size(); i < n; i++) {      Task task = _tst.getTask(i);      PlanElement pe = task.getPlanElement();      if (pe != null) {        _tst.setAllocationResult(i, pe.getEstimatedResult());      }    }    return _tst;  }