\begin{figure*}
     \centering
     \begin{subfigure}[b]{0.24\textwidth}
         \scalebox{0.95}{
         \includegraphics[width=\textwidth]{figures/num_factors/citeulike_recall_10.png}
         }
         \caption{Recall@10 on Citeulike-a}
         \label{fig:citeulike_K_J_recall_10}
     \end{subfigure}%
     \begin{subfigure}[b]{0.24\textwidth}
         \scalebox{0.95}{
         \includegraphics[width=\textwidth]{figures/num_factors/citeulike_ndcg_10.png}
         }
         \caption{NDCG@10 on Citeulike-a}
         \label{fig:citeulike_K_J_ndcg_10}
     \end{subfigure}
     \begin{subfigure}[b]{0.24\textwidth}
         \scalebox{0.95}{
         \includegraphics[width=\textwidth]{figures/num_factors/cellphones_recall_10.png}
         }
         \caption{Recall@10 on Cell Phones}
         \label{fig:cellphones_K_J_recall_10}
     \end{subfigure}
     \begin{subfigure}[b]{0.24\textwidth}
         \scalebox{0.95}{
         \includegraphics[width=\textwidth]{figures/num_factors/cellphones_ndcg_10.png}
         }
         \caption{NDCG@10 on Cell Phones}
         \label{fig:cellphones_K_J_ndcg_10}
     \end{subfigure}
     \hfill
     \begin{subfigure}[b]{0.24\textwidth}
         \scalebox{0.95}{
         \includegraphics[width=\textwidth]{figures/num_factors/movielens_recall_10.png}
         }
         \caption{Recall@10 on MovieLens}
         \label{fig:movielens_K_J_rec_10}
     \end{subfigure}
     \begin{subfigure}[b]{0.24\textwidth}
         % \centering
         \scalebox{0.95}{
         \includegraphics[width=\textwidth]{figures/num_factors/movielens_ndcg_10.png}
         }
         \caption{NDCG@10 on MovieLens}
         \label{fig:movielens_K_J_ndcg_10}
     \end{subfigure}
     \begin{subfigure}[b]{0.24\textwidth}
         \scalebox{0.95}{
         \includegraphics[width=\textwidth]{figures/num_factors/videogames_recall_10.png}
         }
         \caption{Recall@10 on Video Games}
         \label{fig:videogames_K_J_rec_10}
     \end{subfigure}
     \begin{subfigure}[b]{0.24\textwidth}
         % \centering
         \scalebox{0.95}{
         \includegraphics[width=\textwidth]{figures/num_factors/videogames_ndcg_10.png}
         }
         \caption{NDCG@10 on Video Games}
         \label{fig:videogames_K_J_ndcg_10}
     \end{subfigure}
     % \hfill
     % \begin{subfigure}[b]{0.32\textwidth}
     %     \scalebox{0.95}{
     %     \includegraphics[width=\textwidth]{figures/num_factors/citeulike_recall_50.png}
     %     }
     %     \caption{Recall@50 on Citeulike-a}
     %     \label{fig:citeulike_K_J_recall_50}
     % \end{subfigure}
     % \hfill
     % \begin{subfigure}[b]{0.32\textwidth}
     %     \scalebox{0.95}{
     %     \includegraphics[width=\textwidth]{figures/num_factors/cellphones_recall_50.png}
     %     }
     %     \caption{Recall@50 on Cell Phones}
     %     \label{fig:cellphones_K_J_recall_50}
     % \end{subfigure}
     % \hfill
     % \begin{subfigure}[b]{0.32\textwidth}
     %     \scalebox{0.95}{
     %     \includegraphics[width=\textwidth]{figures/num_factors/movielen_recall_50.png}
     %     }
     %     \caption{Recall@50 on MovieLens}
     %     \label{fig:movielens_K_J_rec_50}
     % \end{subfigure}
     % \hfill
     % \begin{subfigure}[b]{0.32\textwidth}
     %     \scalebox{0.95}{
     %     \includegraphics[width=\textwidth]{figures/num_factors/citeulike_ndcg_50.png}
     %     }
     %     \caption{NDCG@50 on Citeulike-a}
     %     \label{fig:citeulike_K_J_ndcg_50}
     % \end{subfigure}
     % \hfill
     % \begin{subfigure}[b]{0.32\textwidth}
     %     \scalebox{0.95}{
     %     \includegraphics[width=\textwidth]{figures/num_factors/cellphones_ndcg_50.png}
     %     }
     %     \caption{NDCG@50 on Cell Phones}
     %     \label{fig:cellphones_K_J_ndcg_50}
     % \end{subfigure}
     % \hfill
     % \begin{subfigure}[b]{0.32\textwidth}
     %     \scalebox{0.95}{
     %     \includegraphics[width=\textwidth]{figures/num_factors/movielen_ndcg_50.png}
     %     }
     %     \caption{NDCG@50 on MovieLens}
     %     \label{fig:movielens_K_J_ndcg_50}
     % \end{subfigure}
    \caption{\ourmethod's performance w.r.t. $K$ and $J$.}
    \label{fig:K_J_comp_supp}
\end{figure*}