docs: private WritableDoubleDataStore computeMaxHeight() {
      WritableDoubleDataStore maxheight = DataStoreUtil.makeDoubleStorage(ids, DataStoreFactory.HINT_HOT | DataStoreFactory.HINT_TEMP, 0.);
      DBIDVar v1 = DBIDUtil.newVar();
      for(DBIDIter it = ids.iter(); it.valid(); it.advance()) {
        double d = parentDistance.doubleValue(it);
        if(d > maxheight.doubleValue(it)) {
          maxheight.putDouble(it, d);
        }
        if(d > maxheight.doubleValue(parent.assignVar(it, v1))) {
          maxheight.putDouble(v1, d);
        }
      }
      return maxheight;
    }