pytorch

e9e55885 - Improve Tensor traverse to traverse its grad_fn when possible (#58271)

Improve Tensor traverse to traverse its grad_fn when possible (#58271) Summary: There are two main changes here: - THPVariable will actually visit their grad_fn if there are no other reference to the c++ Tensor and no other reference to the grad_fn. The critical observation compared to the existing comment (thanks Ed!) is that if we also check that the c++ Tensor object is not referenced somewhere else, we're sure that no one can change the grad_fn refcount between the traverse and the clear. - THPVariable don't need a special clear for this new cases as we're the only owner of the c++ Tensor and so the cdata.reset() will necessarily free the Tensor and all its resources. The two tests are to ensure: - That the cycles are indeed collectible by the gc Pull Request resolved: https://github.com/pytorch/pytorch/pull/58271 Reviewed By: ngimel Differential Revision: D28796461 Pulled By: albanD fbshipit-source-id: 62c05930ddd0c48422c79b03118db41a73c1355d