Deprecate variadic inputs of checkpoint_sequential (#21006)
Summary:
I've reported inconsistency between `checkpoint_sequential` and `nn.Sequential` at https://github.com/pytorch/pytorch/issues/19260. Both should provide the same input signature but they don't. I think the consistency is important and I agree with apaszke that `nn.Sequential`'s semantics should be kept instead of `checkpoint_sequential`.
I hope `checkpoint_sequential` raises `TypeError` on variadic arguments since PyTorch 1.2.0. But for now, it's okay just to warn as `DeprecationWarning`. I've talked about this approach with soumith.
Please review this pull request. Any comment will be my pleasure.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/21006
Differential Revision: D15530801
Pulled By: soumith
fbshipit-source-id: 0ceb2cc6a17dcc547d0d00ebaf9df8603be53183
