Thanks. Not sure how to CC.
In https://github.com/pytorch/vision/blob/master/references/detection/train.py 24, collate_fn for torch.utils.data.DataLoader seems to be the one in “utils.py”, which returns a tuple. The model in that file gets paralleized with torch.nn.parallel.DistributedDataParallel (I understand its different from torch.nn.DataParallel), and trained with “train_one_epoch”. I tried torch.nn.parallel.DistributedDataParallel in the way mentioned in the last part of the posted question, but was unsuccessful