lixin

Results 3 issues of lixin

At the beginning of the training, the PSNR is only about 10dB and it has been oscillating around 10, which does not seem to converge

just like this, which D has a very small loss ![image](https://user-images.githubusercontent.com/12711390/63330818-0ede2c80-c367-11e9-943a-1bf358e90ccc.png)