Reference
- https://blog.csdn.net/a358463121/article/details/52562940
- https://blog.csdn.net/jinping_shi/article/details/78334362
- https://blog.csdn.net/weixin_41947081/article/details/81105555
- https://blog.csdn.net/jinping_shi/article/details/53444100
- Click-Through Rate Estimation for Rare Events in Online Advertising