NVIDIA / NVIDIA/apex

Is distributed package slower than nn.DataParallel?

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Description

First of all, I really appreciate to NVIDIA team which made the apex packages.

I have a question about the speed between apex distributed module and torch's DataParallel module.

If I can train the dataset with batch_size 256 using 4 gpus which model uses DataParallel module, I can also train the dataset with batch_size 64 at each gpu (4 gpus * 64 batch_size = 256) which model uses apex distributed package, right? (ex, python -m torch.distributed.launch --nproc_per_node=4 train.py)

But in my experiment, the training time was different. it was about four times of the model using DataParallel module.
I'm curious about this result... Is it right? or did I make a mistake?

Thanks!

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Research direction

The report names train.py and the torch.distributed.launch command but provides no other files, tests, or reproducible configuration. Start by comparing the DataParallel and distributed launch setups using the supplied command; done requires a documented, reproducible explanation of the timing difference.

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Assessment

Tech stack
python
Domain
distributed-systems, machine-learning
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Needs clarification
Newbie friendliness
20/100

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