Are images and labels shuffled through the dataloader

[JSGrondin]

❔Question

When looking at the function create_dataloader in dataset.py, I see that the dataloader doesn't include the argument shuffle=True, which means the data is not shuffled after each epoch. It is not clear to me whether the data is at least shuffled once at the beginning of training when shuffle=False or if the data is simply loaded in the alphanumerical order of the image/label file names? Could anyone clarify this please?

Additional context

[github-actions]

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[glenn-jocher]

@JSGrondin data is shuffled for training and sorted by aspect ratio for batched rectangular inference during validation.

[JSGrondin]

Many thanks!

[github-actions]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[sramakrishnan247]

@glenn-jocher

@JSGrondin data is shuffled for training and sorted by aspect ratio for batched rectangular inference during validation.
Can you please tell me where exactly this is happening?

[glenn-jocher]

@JSGrondin in the dataloader:

yolov5/utils/datasets.py

Line 341 in 9d87307

class LoadImagesAndLabels(Dataset): # for training/testing

[glenn-jocher]

@JSGrondin @sramakrishnan247 good news 😃! Your original issue may now be fixed ✅ in PR #5623 by @werner-duvaud. This PR turns on shuffling in the YOLOv5 training DataLoader by default, which was missing until now. This works for all training formats: CPU, Single-GPU, Multi-GPU DDP.

train_loader, dataset = create_dataloader(train_path, imgsz, batch_size // WORLD_SIZE, gs, single_cls,
                                          hyp=hyp, augment=True, cache=opt.cache, rect=opt.rect, rank=LOCAL_RANK,
                                          workers=workers, image_weights=opt.image_weights, quad=opt.quad,
                                          prefix=colorstr('train: '), shuffle=True)  # <--- NEW

I evaluated this PR against master on VOC finetuning for 50 epochs, and the results show a slight improvement in most metrics and losses, particularly in objectness loss and [email protected], perhaps indicating that the shuffle addition may help delay overtraining.

https://wandb.ai/glenn-jocher/VOC

To receive this update:

• Git – git pull from within your yolov5/ directory or git clone https://github.com/ultralytics/yolov5 again
• PyTorch Hub – Force-reload model = torch.hub.load('ultralytics/yolov5', 'yolov5s', force_reload=True)
• Notebooks – View updated notebooks
• Docker – sudo docker pull ultralytics/yolov5:latest to update your image

Thank you for spotting this issue and informing us of the problem. Please let us know if this update resolves the issue for you, and feel free to inform us of any other issues you discover or feature requests that come to mind. Happy trainings with YOLOv5 🚀!

[kevinconka]

@JSGrondin data is shuffled for training and sorted by aspect ratio for batched rectangular inference during validation.

I would like to shuffle my validation data so that in clearML I can see 'shuffled' samples. I have tried the following in val.py but did not work:

Is there something I am missing?

[glenn-jocher]

@kevinconka shuffling in validation set is irrelevant for metrics purposes.