Remove Half support in binary cross entropy and some activation functions on CPU (#33206)
Summary:
For reasons similar to https://github.com/pytorch/pytorch/issues/33021. Note that the support of half type has
not been available in any releases yet so it should be safe to remove (All forward ones concerning this PR were added in daef363b15c8a3aaaed09892004dc655df76ff81 and 8cb05e72c69fdd837548419770f3f1ba9807c16d)
Pull Request resolved: https://github.com/pytorch/pytorch/pull/33206
Differential Revision: D19861137
Pulled By: ezyang
fbshipit-source-id: 38a3a398a716a782c26a611c56ddeab7eb7ac79e
