static MultiMap<S, WebNode> ai_indexWebs_parallel2(Collection<Web> webs) ctex {
  print("Making index in parallel.");
  
  final MultiMap<S, WebNode> index = caseInsensitiveMultiMap();
  for (MultiMap<S, WebNode> ind : parallelMap(chunksOf1000(webs), f ai_indexWebs_serial))
    index.putAll(ind);

  ret index;
}