static MultiMap<S, WebNode> ai_indexWebs_parallel2(Collection<Web> webs) ctex {
  print("Making index in parallel.");
  
  time "Parallel indexing" {
    L<MultiMap<S, WebNode>> indexes = parallelMap(chunksOf1000(webs), f ai_indexWebs_serial);
  }
  
  time "Tying up" {
    MultiMap<S, WebNode> index = caseInsensitiveSyncListMultiMap();
    for (MultiMap<S, WebNode> i : indexes)
      index.putAll(i);
  }

  ret index;
}