Loop Refactor 5/N - Prediction Loop

[awaelchli]

What does this PR do?

This was originally the full Loop Refactor POC PR which got split up into multiple parts #7871, #7985, #7990, #8056 and what remains now is the prediction loop refactor.

This PR now only contains the Prediction Loop refactors. There are two new classes based on the existing interface in master:

• PredictionDataLoaderLoop: Loops over all dataloaders and for each runs a PredictionEpochLoop
• PredictionEpochLoop: Loops over a single dataloader of prediction batches

After merge:

• Follow up on TODOs in TODO tracker for ongoing training loop refactors #7938

• Related PRs for review: restrict public interface of training loop #8024 , rename old Trainer.train_loop -> Trainer.fit_loop  #8025

Before submitting

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co-authored by @justusschock

[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 2021-06-23 07:49:52 UTC

[codecov]

Codecov Report

Merging #7700 (5ca00bd) into master (58b47da) will decrease coverage by 0%.
The diff coverage is 98%.

@@          Coverage Diff           @@
##           master   #7700   +/-   ##
======================================
- Coverage      92%     91%   -0%     
======================================
  Files         210     211    +1     
  Lines       13634   13669   +35     
======================================
- Hits        12501   12500    -1     
- Misses       1133    1169   +36     

[Borda]

cool branch name refactor/loops_everywhere :D

[tchaton]

LGTM !