Align ddp and ddp-spawn strategies in setting up the environment

[awaelchli]

What does this PR do?

Aligns the regular ddp strategy and the ddp spawn strategy in setting up the environment (through the method setup_environement which is called in the Trainer._run).

Before:

DDP: Setup environment in setup_environment method/hook. DDPSpawn: At spawn time, in worker_setup function (slightly earlier than setup_environment method/hook

Now:

Both DDP and DDPSpawn set the same variables in setup_environment method.

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Did you have fun?

I made sure I had fun coding 🙃

cc @justusschock @awaelchli @rohitgr7 @kaushikb11 @akihironitta

[ananthsub]

I believe this will be a prerequisite for further consolidation efforts like https://github.com/PyTorchLightning/pytorch-lightning/pull/11021 and https://github.com/PyTorchLightning/pytorch-lightning/pull/11020 by moving up the setup_environment of DDP and TPU spawn

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This pull request has been automatically marked as stale because it has not had recent activity. It will be closed in 7 days if no further activity occurs. If you need further help see our docs: https://pytorch-lightning.readthedocs.io/en/latest/generated/CONTRIBUTING.html#pull-request or ask the assistance of a core contributor here or on Slack. Thank you for your contributions.

[tchaton]

Hey @awaelchli. What is the status on this PR ?

[awaelchli]

The status is that I'm currently working on this and once #11163 is merged this will pretty much be ready.

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This pull request has been automatically marked as stale because it has not had recent activity. It will be closed in 7 days if no further activity occurs. If you need further help see our docs: https://pytorch-lightning.readthedocs.io/en/latest/generated/CONTRIBUTING.html#pull-request or ask the assistance of a core contributor here or on Slack. Thank you for your contributions.

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This pull request is going to be closed. Please feel free to reopen it create a new from the actual master.

[stale[bot]]

This pull request has been automatically marked as stale because it has not had recent activity. It will be closed in 7 days if no further activity occurs. If you need further help see our docs: https://pytorch-lightning.readthedocs.io/en/latest/generated/CONTRIBUTING.html#pull-request or ask the assistance of a core contributor here or on Slack. Thank you for your contributions.

[stale[bot]]

This pull request is going to be closed. Please feel free to reopen it create a new from the actual master.

[stale[bot]]

This pull request has been automatically marked as stale because it has not had recent activity. It will be closed in 7 days if no further activity occurs. If you need further help see our docs: https://pytorch-lightning.readthedocs.io/en/latest/generated/CONTRIBUTING.html#pull-request or ask the assistance of a core contributor here or on Slack. Thank you for your contributions.

[carmocca]

@awaelchli is this important for Lite? Do you want to apply these changes to the Lite versions already in #14670 and #14675?

[awaelchli]

@carmocca I would say quite important for #14707. Yes, I can integrate this into the two PRs. The PR was ready long before starting with Lite, I should have pushed harder to get this merged 😅

[Borda]

@awaelchli mind checking the conflicts... :otter:

[carmocca]

:tada:

[awaelchli]

🥳