public void filterParentAndChildDoc(){
		System.out.println("Before filtering\t"+m_corpus.getSize());
		int corpusSize = m_corpus.getCollection().size();
		ArrayList<Integer> removeIndexList = new ArrayList<Integer>();
		
		int numberOfComments = 0;
		
		for (int i = corpusSize - 1; i > -1; i--) {
			// for (int i = 0; i < corpusSize; i++) {
			_Doc d = m_corpus.getCollection().get(i);
			if(d instanceof _ParentDoc){
				_ParentDoc pDoc = (_ParentDoc)d;
				if(pDoc.m_childDocs.size()>8){
					numberOfComments += 1;
				}
				if(pDoc.m_childDocs.size()==0)
					removeIndexList.add(i);
			}
		}
		
		System.out.println("number of comments > 8 \t"+numberOfComments);
		
		for (int i : removeIndexList) {
			_Doc d = m_corpus.getCollection().get(i);
			System.out
					.println("removing parent without child \t" + d.getName());
			m_corpus.getCollection().remove(i);

		}

		System.out.println("after filtering\t"+m_corpus.getSize());
	}