I also met this problem in my project (See my answer at https://github.com/xingyizhou/pytorch-pose-hg-3d/issues/16 91 and https://github.com/bearpaw/pytorch-pose/issues/33 59). In short, down-grading pytorch version to 0.1.12 will resolve the problem. But I really don’t know what happens to the BN implementation from 0.1.12 to the later versions …