I found the reason.
Other discussion say that compatibility should bigger than 3.0, K20 is 3.5.
I thought that would be ok. However, I guess other factor will affect this.
The result is because of the old GPU. Cuda 8.0 on K20 should do the work.
If your device is cuda 9.0 and you don’t have the permission to degrade this version.
I suggest you change your GPU.