in detector/train.py [0:0]
def _all_reduce_dict(d, device):
# wrap in tensor and use reduce to gpu0 tensor
output_d = {}
for (key, value) in sorted(d.items()):
tensor_input = torch.tensor([[value]]).to(device)
torch.distributed.all_reduce(tensor_input)
output_d[key] = tensor_input.item()
return output_d