public double getBiScore(String parent, String lchild, String rchild){
    	double biscore=0;
    	List<BinaryRule> rules = getBinaryRulesByParent(parent);
    	for(int i=0;i<rules.size();i++){
			String cc = rules.get(i).getLeftChild();
			if (cc.equals(lchild)){
				List<BinaryRule> rules1 = getBinaryRulesByLeftChild(lchild);
				for(int j=0;j<rules1.size();j++){
					String cc2 = rules1.get(j).getRightChild();
					if (cc2.equals(rchild)){
						biscore = rules1.get(j).getScore();
					}
				}
			}
		}
    	return Math.log(biscore);
    }