docs: private final void resizeClean() {
      //must resize, but are we at tgt size?
      final int lgTgtLongs = lgNomLongs_ + 1;
      if (lgTgtLongs > lgArrLongs_) {
        //not yet at tgt size
        final ResizeFactor rf = getResizeFactor();
        final int lgDeltaLongs = lgTgtLongs - lgArrLongs_; //must be > 0
        final int lgResizeFactor = max(min(rf.lg(), lgDeltaLongs), 1); //rf_.lg() could be 0
        forceResizeCleanCache(lgResizeFactor);
      }
      else {
        //at tgt size or larger, no dirty values, must take drastic measures, very rare.
        forceResizeCleanCache(1);
      }
    }