The unsupervised training method in the README breaks

[CoinCheung]

Hi,

Thanks for releasing the code!!! I think the launching method in the README should be updated a bit. I run like this:

python main_moco.py -a resnet50 --lr 0.03 --batch-size 256 --world-size 1 --rank 0 /data2/zzy/imagenet 

And I got the error of:

Traceback (most recent call last):
  File "main_moco.py", line 402, in <module>
    main()
  File "main_moco.py", line 133, in main
    main_worker(args.gpu, ngpus_per_node, args)
  File "main_moco.py", line 186, in main_worker
    raise NotImplementedError("Only DistributedDataParallel is supported.")
NotImplementedError: Only DistributedDataParallel is supported.

I think the rank is not correctly assigned. Did I miss anything useful ?

[KaimingHe]

Please follow the command line in the README:
python main_moco.py \ -a resnet50 \ --lr 0.03 \ --batch-size 256 \ --dist-url 'tcp://localhost:10001' --multiprocessing-distributed --world-size 1 --rank 0 \ [your imagenet-folder with train and val folders]

Specifically, note --dist-url 'tcp://localhost:10001' --multiprocessing-distributed.