lightly-ai / lightly-ai/lightly

OoM issue with multiple gpus using Distributed Data Parallel (DDP) training

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Dominant language
Python
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Description

When I run this example [runs on multiple gpus using Distributed Data Parallel (DDP) training](https://docs.lightly.ai/self-supervised-learning/examples/simclr.html) on AWS SageMaker with 4 GPUS and a batch_size of 8192, I got a OoM issue despite the 96GiB capacity:
````
Tried to allocate 4.00 GiB. GPU 2 has a total capacity of 21.99 GiB of which 1.21 GiB is free. Including non-PyTorch memory, this process has 20.77 GiB memory in use.
````

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First steps

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Research direction

Start with the linked SimCLR example and its Distributed Data Parallel training setup, then reproduce the reported run on AWS SageMaker with four GPUs and batch_size 8192. Investigate the reported GPU memory allocation and determine a documented or verified change that prevents the out-of-memory failure under this configuration.

Written by the indexing model from the issue text.

Assessment

Tech stack
aws, python, pytorch
Domain
distributed-systems, machine-learning
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Needs clarification
Newbie friendliness
25/100

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