docs: synchronized void computeTrees() {
          boolean changed;
          try {
              createBuffers();
              do {
                  switchBuffers();
                  changed = computeOneLevel();
  //System.out.println("Tree obj.   "+heap.idToOffsetMap.treeObj);
  //if (changed) System.out.println("Next level  "+nextLevelSize);
              } while (changed);
          } catch (IOException ex) {
              ex.printStackTrace();
          }
          deleteBuffers();
  //System.out.println("Done!");
      }