Department of Computer Science, National Tsing Hua University, Hsinchu 30013, Taiwan.|Department of Computer Science, National Tsing Hua University, Hsinchu 30013, Taiwan.|Department of Computer Science, National Tsing Hua University, Hsinchu 30013, Taiwan.|Department of Computer Science, National Tsing Hua University, Hsinchu 30013, Taiwan.|Department of Computer Science, National Tsing Hua University, Hsinchu 30013, Taiwan.