private void compute(List<String> words) {
		long cId = comments2Words.size() + 1;
		comments2Words.put(cId, words);
		for (String word: words) {
			if (words2Comments.containsKey(word)) {
				List<Long> commentIds = words2Comments.get(word);
				commentIds.add(cId);
			} else {
				List<Long> commentIds = new ArrayList<Long>();
				commentIds.add(cId);
				words2Comments.put(word, commentIds);
			}
		}
	}