private double computeLogLikelihood(Documents docSet) {
		// TODO Auto-generated method stub
    	 /*
         * Compute the log likelihood of generation the corpus
         * 
         * L = sum_i {n(d_i) * [sum_j( n(d_i, w_j) / n(d_i) * log sum_k p(z_k|d_i)*p(w_j|z_k))]}
         * 
         */
    	 double L = 0.0;
    	 for (int i = 0; i < N; i++) {
    		 double docISize = docSet.docs.get(i).docWords.length;
    		 double sumM = 0.0;
    		 for (int j = 0; j < M; j++) { 
    			 double sumK = 0.0;
    			 for(int k = 0; k < topicNum; k++){
    				 sumK += docTopicPros[i][k] * topicTermPros[k][j];
    			 }
    			 //System.out.println("sumK: " + sumK);
    			 sumM += (double)docTermMatrix[i][j] / docISize * Math.log10(sumK);
    		 }
    		 //System.out.println("sumM: " + sumM);
             L += docISize * sumM;
    	 }
		return L;
	}