how to use multiple gpu, can u show example ?

[ucalyptus2]

@wangjk666 greetings, please show example for multi gpu setting in same cluster. Single Machine with 8 GPUs I have.

[ucalyptus2]

 'TRAIN': {'CHECKPOINT_EPOCH_RESET': False,
           'CHECKPOINT_LOAD_PATH': '/ingenuity_NAS/21sd45_nas/21sd45_mount/checkpoints/Xception_FFDF_epoch_00075.pyth',
           'CHECKPOINT_PERIOD': 5,
           'CHECKPOINT_SAVE_PATH': '/ingenuity_NAS/21sd45_nas/21sd45_mount/',
           'ENABLE': True,
           'EVAL_PERIOD': 1,
           'MAX_EPOCH': 200}}
[10/11 19:32:47][INFO] build_helper.py:  81: MODEL_NAME: Xception
Traceback (most recent call last):
  File "/home/21sd45/PyDeepFakeDet/run.py", line 26, in <module>
    main()
  File "/home/21sd45/PyDeepFakeDet/run.py", line 20, in main
    launch_func(cfg=cfg, func=train)
  File "/home/21sd45/PyDeepFakeDet/tools/utils.py", line 94, in launch_func
    torch.multiprocessing.spawn(
  File "/home/21sd45/miniconda3/envs/new/lib/python3.9/site-packages/torch/multiprocessing/spawn.py", line 240, in spawn
    return start_processes(fn, args, nprocs, join, daemon, start_method='spawn')
  File "/home/21sd45/miniconda3/envs/new/lib/python3.9/site-packages/torch/multiprocessing/spawn.py", line 198, in start_processes
    while not context.join():
  File "/home/21sd45/miniconda3/envs/new/lib/python3.9/site-packages/torch/multiprocessing/spawn.py", line 160, in join
    raise ProcessRaisedException(msg, error_index, failed_process.pid)
torch.multiprocessing.spawn.ProcessRaisedException: 

-- Process 3 terminated with the following error:
Traceback (most recent call last):
  File "/home/21sd45/miniconda3/envs/new/lib/python3.9/site-packages/torch/multiprocessing/spawn.py", line 69, in _wrap
    fn(i, *args)
  File "/home/21sd45/PyDeepFakeDet/tools/train.py", line 151, in train
    model = build_model(cfg)
  File "/home/21sd45/PyDeepFakeDet/PyDeepFakeDet/utils/build_helper.py", line 89, in build_model
    device_ids=[int(os.environ['LOCAL_RANK'])]
  File "/home/21sd45/miniconda3/envs/new/lib/python3.9/os.py", line 679, in __getitem__
    raise KeyError(key) from None
KeyError: 'LOCAL_RANK'

[ucalyptus2]

@zhangchaosd