Thank you for your kind answer.I understand the ‘state’. I guess it refers a weight in a  neural network right? Quantization is something I’ve never seen so I need to see youre reference. However, I’m little bit confuse becuase I think there is no conclusion for some kind of a threshold that using functional or Module. Maybe that’s why I’m not an native english speaker.
I apologise for the inconvenience but if I’m not asking you this question, I will never know. Please excuse me for bothering you. And I want to quote what you mentioned just like you did to mine, but I don’t know how to do it so I just write them down.

That is more “if you implement something new, provide both because you don’t know which is more convenient to your users”

I don’t want to make an activation function. I just want to know proper way to use them (softmax, ReLU, whatever it is). However, I guess there is no clear standard for it. The functional are not saved in the stae of a neural network so I should avoid it if I want to save them as state_dict right?

For softmax, and if you aren’t building a Sequential , I’d use the functional interface.

Why would you do that? What’s the beneficial of using functional interface instead of Module?
Once again, I apologise for the inconvenience.