public static double calculate_ndcg(String query, LinkedList<String> url_list)
	{
		HashMap<String,LinkedList<String>> google_resultmap=create_google_map();
		
		Iterator<String> It = url_list.iterator();
	    LinkedList<String> google_querymap = google_resultmap.get(query);
	    if(google_querymap==null)return 1.0;
	    String url;
	    int count = 0, indx;
	    double ndcg = 0;
	    while(It.hasNext() && count <5)
	    {
	    	url = It.next();
	    	count++;	
	    	if(google_querymap.contains(url))
	    	{
	    		
	    		indx = google_querymap.indexOf(url);
	    		System.out.println("indx " + indx);
	    		ndcg += (Math.pow(2.0, 5-(indx)) - 1)/((Math.log10(count + 1)/Math.log10(2)));  		
	    	}
	    }
		
	    ndcg /= (double)45.64282878502658;
		return ndcg;
	}