move amp checkpoint state management to precision plugin

[awaelchli]

What does this PR do?

Part of #7652 (splitting down diff)

Makes checkpoint saving/loading logic agnostic to precision being used.
This is just a refactor, no changes to the current behavior are intended.

Before submitting

• Was this discussed/approved via a GitHub issue? (not for typos and docs)
• Did you read the contributor guideline, Pull Request section?
• 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)

PR review

Anyone in the community is free to review the PR once the tests have passed.
Before you start reviewing make sure you have read Review guidelines. In short, see the following bullet-list:

• Is this pull request ready for review? (if not, please submit in draft mode)
• Check that all items from Before submitting are resolved
• Make sure the title is self-explanatory and the description concisely explains the PR
• Add labels and milestones (and optionally projects) to the PR so it can be classified

Did you have fun?

Make sure you had fun coding 🙃

[pep8speaks]

Hello @awaelchli! Thanks for updating this PR.

There are currently no PEP 8 issues detected in this Pull Request. Cheers! 🍻

Comment last updated at 2021-06-07 07:08:27 UTC

[codecov]

Codecov Report

Merging #7831 (07e4294) into master (1da1898) will decrease coverage by 0%.
The diff coverage is 88%.

@@          Coverage Diff           @@
##           master   #7831   +/-   ##
======================================
- Coverage      93%     92%   -0%     
======================================
  Files         202     202           
  Lines       13050   13053    +3     
======================================
- Hits        12085   12049   -36     
- Misses        965    1004   +39     

[justusschock]

LGTM. Just a question: could we maybe group those args under a precision subdict so that we don't pollute the global checkpoint namespace?

[awaelchli]

would be great but then we would have to deal with backward compatibility too 🙈
can do a follow up :)

[carmocca]

Want to update the CHANGELOG for this?