train error

Traceback (most recent call last): File "main.py", line 132, in <module> launch( File "/home/jyw/anaconda3/envs/ViTMatte/lib/python3.8/site-packages/detectron2/engine/launch.py", line 87, in launch main_func(*args) File "main.py", line 126, in main do_train(args, cfg) File "main.py", line 78, in do_train train_loader = instantiate(cfg.dataloader.train) File "/home/jyw/anaconda3/envs/ViTMatte/lib/python3.8/site-packages/detectron2/config/instantiate.py", line 67, in instantiate cfg = {k: instantiate(v) for k, v in cfg.items()} File "/home/jyw/anaconda3/envs/ViTMatte/lib/python3.8/site-packages/detectron2/config/instantiate.py", line 67, in <dictcomp> cfg = {k: instantiate(v) for k, v in cfg.items()} File "/home/jyw/anaconda3/envs/ViTMatte/lib/python3.8/site-packages/detectron2/config/instantiate.py", line 83, in instantiate return cls(**cfg) File "/home/jyw/anaconda3/envs/ViTMatte/lib/python3.8/site-packages/torch/utils/data/distributed.py", line 68, in __init__ num_replicas = dist.get_world_size() File "/home/jyw/anaconda3/envs/ViTMatte/lib/python3.8/site-packages/torch/distributed/distributed_c10d.py", line 1181, in get_world_size return _get_group_size(group) File "/home/jyw/anaconda3/envs/ViTMatte/lib/python3.8/site-packages/torch/distributed/distributed_c10d.py", line 566, in _get_group_size default_pg = _get_default_group() File "/home/jyw/anaconda3/envs/ViTMatte/lib/python3.8/site-packages/torch/distributed/distributed_c10d.py", line 697, in _get_default_group raise RuntimeError( RuntimeError: Default process group has not been initialized, please make sure to call init_process_group.