1 Introduction
Nowadays, more and more researchers and enterprises found broad artificial Intelligent applications based on deep learning methods, which led to breakthroughs in many tasks, such as risk assessment, medical predictions, and face recognition. A factor that drives this success is the rapid growth of data. As the training datasets grow bigger and more diverse, deep neural network models become better. Therefore, the large-scale data collection for deep learning algorithms is very important for training appropriate models. For example, Internet companies regularly collect users’ on-line activities and browsing behavior to build more accurate recommender systems.