static MultiMap<S, WebNode> ai_indexWebs_parallel(Collection<Web> webs) ctex {
  print("Making index in parallel.");
  final MultiMap<S, WebNode> index = caseInsensitiveMultiMap();
  
  int queueSize = numberOfCores();
  NotifyingBlockingThreadPoolExecutor e = new(numberOfCores(), queueSize, 15, TimeUnit.SECONDS);
    
  try {
    for (final L<Web> l : chunksOf1000(webs)) {
      e.execute(r { pcall {
        for (Web web : l)
          ai_addWebToIndex(index, web);
      }});
    }
    e.shutdown();
    e.awaitTermination(1, TimeUnit.DAYS);
  } finally {
    e.shutdown();
  }
  
  ret index;
}