AssertionError: Default process group is not initialized

[kukby]

I have meet a problem, Can you solve it? Thanks!
Traceback (most recent call last):
File "train_autodeeplab.py", line 332, in
main()
File "train_autodeeplab.py", line 321, in main
trainer = Trainer(args)
File "train_autodeeplab.py", line 47, in init
self.train_loaderA, self.train_loaderB, self.val_loader, self.test_loader, self.nclass = make_data_loader(args, **kwargs)
File "/home/kukby/AutoML-new_master/dataloaders/init.py", line 13, in make_data_loader
sampler1 = torch.utils.data.distributed.DistributedSampler(train_set1)
File "/home/kukby/.local/lib/python3.6/site-packages/torch/utils/data/distributed.py", line 30, in init
num_replicas = dist.get_world_size()
File "/home/kukby/.local/lib/python3.6/site-packages/torch/distributed/distributed_c10d.py", line 584, in get_world_size
return _get_group_size(group)
File "/home/kukby/.local/lib/python3.6/site-packages/torch/distributed/distributed_c10d.py", line 200, in _get_group_size
_check_default_pg()
File "/home/kukby/.local/lib/python3.6/site-packages/torch/distributed/distributed_c10d.py", line 191, in _check_default_pg
"Default process group is not initialized"

[ntongzhi]

Have you solved the problem?Please help!