public void printXProportion(String xProportionFile, ArrayList<_Doc> docList) {
		System.out.println("x proportion for parent doc");
		try {
			PrintWriter pw = new PrintWriter(new File(xProportionFile));
			for (_Doc d : docList) {
				if (d instanceof _ParentDoc) {
					for (_ChildDoc doc : ((_ParentDoc) d).m_childDocs) {
						_ChildDoc4BaseWithPhi cDoc = (_ChildDoc4BaseWithPhi) doc;
						pw.print(d.getName() + "\t");
						pw.print(cDoc.getName() + "\t");
						pw.print(cDoc.m_xProportion[0] + "\t");
						pw.print(cDoc.m_xProportion[1]);
						pw.println();
					}
				}
			}

			pw.flush();
			pw.close();
		} catch (Exception e) {
			e.printStackTrace();
		}

	}