public void run()
{
Map<Integer, Integer> counts = pre_results[index] = new PDefaultMap<Integer, Integer>(0);
for (int i = start; i < stop; i++) {
Webdoc doc = Generator.documents_array[i];
for (int word_id : doc.words) {
counts.put(Env.canonicalInteger(word_id),
counts.get(word_id) + 1);
}