Nearest interpolation gpu implementation fix [Resolves issue #38985] (#39055)
Summary:
fix nearest upsample dgrad bug, where window computation was wrong previously;
fix python test where previously GPU implementation was not tested;
Pull Request resolved: https://github.com/pytorch/pytorch/pull/39055
Differential Revision: D21763242
Pulled By: albanD
fbshipit-source-id: 9b1d5365f40176450f529136110542fd36bd7f58
