AssertionError: Default process group is not initialized

报错：

  File "/home/ubuntu/bigdisk/part2/Swin-Transformer-Object-Detection/mmdet/models/roi_heads/bbox_heads/convfc_bbox_head.py", line 139, in forward
    x = conv(x)
  File "/home/ubuntu/anaconda3/envs/swin/lib/python3.7/site-packages/torch/nn/modules/module.py", line 532, in __call__
    result = self.forward(*input, **kwargs)
  File "/home/ubuntu/anaconda3/envs/swin/lib/python3.7/site-packages/mmcv/cnn/bricks/conv_module.py", line 203, in forward
    x = self.norm(x)
  File "/home/ubuntu/anaconda3/envs/swin/lib/python3.7/site-packages/torch/nn/modules/module.py", line 532, in __call__
    result = self.forward(*input, **kwargs)
  File "/home/ubuntu/anaconda3/envs/swin/lib/python3.7/site-packages/torch/nn/modules/batchnorm.py", line 458, in forward
    world_size = torch.distributed.get_world_size(process_group)
  File "/home/ubuntu/anaconda3/envs/swin/lib/python3.7/site-packages/torch/distributed/distributed_c10d.py", line 586, in get_world_size
    return _get_group_size(group)
  File "/home/ubuntu/anaconda3/envs/swin/lib/python3.7/site-packages/torch/distributed/distributed_c10d.py", line 202, in _get_group_size
    _check_default_pg()
  File "/home/ubuntu/anaconda3/envs/swin/lib/python3.7/site-packages/torch/distributed/distributed_c10d.py", line 193, in _check_default_pg
    "Default process group is not initialized"
AssertionError: Default process group is not initialized

解决方法：

把配置文件中的SyncBN全部改为BN即可。