Fabric checkpointing 3/n: Implement missing get_module_state_dict for strategies

[awaelchli]

What does this PR do?

Follow up to #16452

The two strategies, DDP and DP, need to implement the get_module_state_dict hook in order to correctly retrieve the state dict when save_checkpoint is called. Otherwise, the parameter keys are prefixed with the "module" key.

All other strategies handle don't need this:

• All single device strategies, they aren't doing wrapping
• XLA: Doesn't do wrapping
• DeepSpeed: Handled through deepspeed engine's checkpointing mechanism
• FSDP: Checkpointing not yet implemented

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• Did you update the CHANGELOG? (not for typos, docs, test updates, or internal minor changes/refactorings)

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I made sure I had fun coding 🙃

cc @Borda @awaelchli @carmocca @justusschock

[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_fabric/strategies/ddp.py, src/lightning_fabric/strategies/dp.py.

🟢 pytorch_lightning: Azure GPU

Check ID	Status
pytorch-lightning (GPUs)	success	✅

These checks are required after the changes to src/lightning_fabric/strategies/ddp.py, src/lightning_fabric/strategies/dp.py.

🟢 pytorch_lightning: Azure HPU

Check ID	Status
pytorch-lightning (HPUs)	success	✅

These checks are required after the changes to src/lightning_fabric/strategies/ddp.py, src/lightning_fabric/strategies/dp.py.

🟢 pytorch_lightning: Azure IPU

Check ID	Status
pytorch-lightning (IPUs)	success	✅

These checks are required after the changes to src/lightning_fabric/strategies/ddp.py, src/lightning_fabric/strategies/dp.py.

🟢 lightning_fabric: CPU workflow

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

These checks are required after the changes to src/lightning_fabric/strategies/ddp.py, src/lightning_fabric/strategies/dp.py, tests/tests_fabric/strategies/test_ddp.py, tests/tests_fabric/strategies/test_dp.py.

🟢 lightning_fabric: Azure GPU

Check ID	Status
lightning-fabric (GPUs)	success	✅

These checks are required after the changes to src/lightning_fabric/strategies/ddp.py, src/lightning_fabric/strategies/dp.py, tests/tests_fabric/strategies/test_ddp.py, tests/tests_fabric/strategies/test_dp.py.

🟢 mypy

Check ID	Status
mypy	success	✅

These checks are required after the changes to src/lightning_fabric/strategies/ddp.py, src/lightning_fabric/strategies/dp.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, fabric, 3.7)	success	✅
install-pkg (ubuntu-22.04, fabric, 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 (ubuntu-22.04, notset, 3.7)	success	✅
install-pkg (ubuntu-22.04, notset, 3.10)	success	✅
install-pkg (macOS-12, app, 3.7)	success	✅
install-pkg (macOS-12, app, 3.10)	success	✅
install-pkg (macOS-12, fabric, 3.7)	success	✅
install-pkg (macOS-12, fabric, 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 (macOS-12, notset, 3.7)	success	✅
install-pkg (macOS-12, notset, 3.10)	success	✅
install-pkg (windows-2022, app, 3.7)	success	✅
install-pkg (windows-2022, app, 3.10)	success	✅
install-pkg (windows-2022, fabric, 3.7)	success	✅
install-pkg (windows-2022, fabric, 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	✅
install-pkg (windows-2022, notset, 3.7)	success	✅
install-pkg (windows-2022, notset, 3.10)	success	✅

These checks are required after the changes to src/lightning_fabric/strategies/ddp.py, src/lightning_fabric/strategies/dp.py.

🟢 link-check

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markdown-link-check	success	✅

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