Activation checkpointing in FSDP without boilerplate

[awaelchli]

What does this PR do?

Fixes #15825

TODO:

• add the same for the PL implementation
• tests
• version check
• docs

Does your PR introduce any breaking changes? If yes, please list them.

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• Was this discussed/approved via a GitHub issue? (not for typos and docs)
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• Did you make sure your PR does only one thing, instead of bundling different changes together?
• Did you make sure to update the documentation with your changes? (if necessary)
• Did you write any new necessary tests? (not for typos and docs)
• Did you verify new and existing tests pass locally with your changes?
• Did you update the CHANGELOG? (not for typos, docs, test updates, or internal minor changes/refactorings)

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Did you have fun?

I made sure I had fun coding 🙃

cc @Borda @carmocca @justusschock @awaelchli

[github-actions]

⚡ Required checks status: All passing 🟢

Groups summary

🟢 pytorch_lightning: Tests workflow

Check ID	Status
pl-cpu (macOS-11, pytorch, 3.8, 1.11)	success	✅
pl-cpu (macOS-11, pytorch, 3.9, 1.12)	success	✅
pl-cpu (macOS-11, pytorch, 3.10, 1.13)	success	✅
pl-cpu (macOS-11, pytorch, 3.8, 1.10, oldest)	success	✅
pl-cpu (ubuntu-20.04, pytorch, 3.8, 1.10)	success	✅
pl-cpu (ubuntu-20.04, pytorch, 3.9, 1.11)	success	✅
pl-cpu (ubuntu-20.04, pytorch, 3.10, 1.12)	success	✅
pl-cpu (ubuntu-20.04, pytorch, 3.10, 1.13)	success	✅
pl-cpu (ubuntu-20.04, pytorch, 3.7, 1.10, oldest)	success	✅
pl-cpu (windows-2022, pytorch, 3.9, 1.11)	success	✅
pl-cpu (windows-2022, pytorch, 3.10, 1.12)	success	✅
pl-cpu (windows-2022, pytorch, 3.10, 1.13)	success	✅
pl-cpu (windows-2022, pytorch, 3.7, 1.10, oldest)	success	✅
pl-cpu (slow, macOS-11, pytorch, 3.7, 1.11)	success	✅
pl-cpu (slow, ubuntu-20.04, pytorch, 3.7, 1.11)	success	✅
pl-cpu (slow, windows-2022, pytorch, 3.7, 1.11)	success	✅
pl-cpu (macOS-11, lightning, 3.8, 1.13)	success	✅
pl-cpu (ubuntu-20.04, lightning, 3.8, 1.13)	success	✅
pl-cpu (windows-2022, lightning, 3.8, 1.13)	success	✅

These checks are required after the changes to src/lightning_lite/strategies/fsdp.py, src/pytorch_lightning/strategies/fully_sharded_native.py, tests/tests_pytorch/strategies/test_ddp_fully_sharded_native.py.

🟢 pytorch_lightning: Azure GPU

Check ID	Status
pytorch-lightning (GPUs)	success	✅

These checks are required after the changes to src/pytorch_lightning/strategies/fully_sharded_native.py, tests/tests_pytorch/strategies/test_ddp_fully_sharded_native.py, src/lightning_lite/strategies/fsdp.py.

🟢 pytorch_lightning: Azure HPU

Check ID	Status
pytorch-lightning (HPUs)	success	✅

These checks are required after the changes to src/lightning_lite/strategies/fsdp.py, src/pytorch_lightning/strategies/fully_sharded_native.py, tests/tests_pytorch/strategies/test_ddp_fully_sharded_native.py.

🟢 pytorch_lightning: Azure IPU

Check ID	Status
pytorch-lightning (IPUs)	success	✅

These checks are required after the changes to src/lightning_lite/strategies/fsdp.py, src/pytorch_lightning/strategies/fully_sharded_native.py, tests/tests_pytorch/strategies/test_ddp_fully_sharded_native.py.

🟢 pytorch_lightning: Docs

Check ID	Status
make-doctest (pytorch)	success	✅
make-html (pytorch)	success	✅

These checks are required after the changes to src/pytorch_lightning/strategies/fully_sharded_native.py, docs/source-pytorch/advanced/model_parallel.rst.

🟢 lightning_lite: CPU workflow

Check ID	Status
lite-cpu (macOS-11, lite, 3.8, 1.11)	success	✅
lite-cpu (macOS-11, lite, 3.9, 1.12)	success	✅
lite-cpu (macOS-11, lite, 3.10, 1.13)	success	✅
lite-cpu (macOS-11, lite, 3.7, 1.10, oldest)	success	✅
lite-cpu (ubuntu-20.04, lite, 3.8, 1.10)	success	✅
lite-cpu (ubuntu-20.04, lite, 3.9, 1.11)	success	✅
lite-cpu (ubuntu-20.04, lite, 3.10, 1.12)	success	✅
lite-cpu (ubuntu-20.04, lite, 3.10, 1.13)	success	✅
lite-cpu (ubuntu-20.04, lite, 3.7, 1.10, oldest)	success	✅
lite-cpu (windows-2022, lite, 3.9, 1.11)	success	✅
lite-cpu (windows-2022, lite, 3.10, 1.12)	success	✅
lite-cpu (windows-2022, lite, 3.10, 1.13)	success	✅
lite-cpu (windows-2022, lite, 3.7, 1.10, oldest)	success	✅
lite-cpu (macOS-11, lightning, 3.8, 1.13)	success	✅
lite-cpu (ubuntu-20.04, lightning, 3.8, 1.13)	success	✅
lite-cpu (windows-2022, lightning, 3.8, 1.13)	success	✅

These checks are required after the changes to src/lightning_lite/strategies/fsdp.py, tests/tests_lite/strategies/test_fsdp.py, tests/tests_lite/strategies/test_fsdp_integration.py.

🟢 lightning_lite: Azure GPU

Check ID	Status
lightning-lite (GPUs)	success	✅

These checks are required after the changes to src/lightning_lite/strategies/fsdp.py, tests/tests_lite/strategies/test_fsdp.py, tests/tests_lite/strategies/test_fsdp_integration.py.

🟢 mypy

Check ID	Status
mypy	success	✅

These checks are required after the changes to src/lightning_lite/strategies/fsdp.py, src/pytorch_lightning/strategies/fully_sharded_native.py.

🟢 install

Check ID	Status
install-pkg (ubuntu-22.04, app, 3.7)	success	✅
install-pkg (ubuntu-22.04, app, 3.10)	success	✅
install-pkg (ubuntu-22.04, lite, 3.7)	success	✅
install-pkg (ubuntu-22.04, lite, 3.10)	success	✅
install-pkg (ubuntu-22.04, pytorch, 3.7)	success	✅
install-pkg (ubuntu-22.04, pytorch, 3.10)	success	✅
install-pkg (ubuntu-22.04, lightning, 3.7)	success	✅
install-pkg (ubuntu-22.04, lightning, 3.10)	success	✅
install-pkg (macOS-12, app, 3.7)	success	✅
install-pkg (macOS-12, app, 3.10)	success	✅
install-pkg (macOS-12, lite, 3.7)	success	✅
install-pkg (macOS-12, lite, 3.10)	success	✅
install-pkg (macOS-12, pytorch, 3.7)	success	✅
install-pkg (macOS-12, pytorch, 3.10)	success	✅
install-pkg (macOS-12, lightning, 3.7)	success	✅
install-pkg (macOS-12, lightning, 3.10)	success	✅
install-pkg (windows-2022, app, 3.7)	success	✅
install-pkg (windows-2022, app, 3.10)	success	✅
install-pkg (windows-2022, lite, 3.7)	success	✅
install-pkg (windows-2022, lite, 3.10)	success	✅
install-pkg (windows-2022, pytorch, 3.7)	success	✅
install-pkg (windows-2022, pytorch, 3.10)	success	✅
install-pkg (windows-2022, lightning, 3.7)	success	✅
install-pkg (windows-2022, lightning, 3.10)	success	✅

These checks are required after the changes to src/lightning_lite/strategies/fsdp.py, src/pytorch_lightning/strategies/fully_sharded_native.py.

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Thank you for your contribution! 💜

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