detach according to the docs:

Returns a new Variable, detached from the current graph.
Result will never require gradient. If the input is volatile, the output will be volatile too.

What does it mean for the variable to be detached and how does it affect performance?
I get the volatile backprop error with detach unless I do fake = Variable(fake.data)
If the idea is to not use volatile then what does it mean for the generator? Wouldn’t it be less efficient?