It’s calling torch._C._functions.BatchNorm
And I think you can find the underlying code here: https://github.com/pytorch/pytorch/blob/master/torch/csrc/autograd/functions/batch_normalization.cpp 1.9k
If you are just trying to understand more generally what is batch normalisation, there is a doc for modules nn.BatchNorm1d/2d/3d: http://pytorch.org/docs/master/nn.html#torch.nn.BatchNorm1d 789