protected void printTopKChild4Parent(String filePrefix, int topK) {
		String topKChild4StnFile = filePrefix + "topChild4Parent.txt";
		try {
			PrintWriter pw = new PrintWriter(new File(topKChild4StnFile));

			for (_Doc d : m_trainSet) {
				if (d instanceof _ParentDoc) {
					_ParentDoc pDoc = (_ParentDoc) d;

					pw.print(pDoc.getName() + "\t");

					for (_ChildDoc cDoc : pDoc.m_childDocs) {
						double docScore = rankChild4ParentBySim(cDoc, pDoc);

						pw.print(cDoc.getName() + ":" + docScore + "\t");

					}

					pw.println();
				}
			}
			pw.flush();
			pw.close();

		} catch (Exception e) {
			e.printStackTrace();
		}
	}