code: public ArrayOfDoublesCompactSketch getResult(final WritableMemory dstMem) {
      if (sketch_.getRetainedEntries() > sketch_.getNominalEntries()) {
        theta_ = Math.min(theta_, sketch_.getNewTheta());
      }
      if (dstMem == null) {
        return new HeapArrayOfDoublesCompactSketch(sketch_, theta_);
      }
      return new DirectArrayOfDoublesCompactSketch(sketch_, theta_, dstMem);
    }
docs: Returns the resulting union in the form of a compact sketch
  @param dstMem memory for the result (can be null)
  @return compact sketch representing the union (off-heap if memory is provided)