Do not modify saved variables in-place for spectral norm during power iteration (#62293)
Summary:
Interestingly enough, the original code did have a mechanism that aims to prevent this very issue:
but it performs a clone AFTER modifying u and v in-place.
This wouldn't work though because we can later use the cloned u and v in operations that save for backward, and the next time we execute forward, we modify the same cloned u and v in-place.
So if the idea is that we want to avoid modifying saved variable in-place we should clone it BEFORE the in-place operation.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/62293
Reviewed By: bdhirsh
Differential Revision: D30489750
Pulled By: soulitzer
fbshipit-source-id: cbe8dea885aef97adda8481f7a822e5bd91f7889
