Enables reload of dataloaders on every n epochs from every epoch

[sidhantls]

What does this PR do?

This PR extends the logic of reloading dataloaders on every epoch allowing DLs to be reloaded every n epochs. It changes the argument from reload_dataloaders_every_epoch to reload_dataloaders_every_n_epochs . The parameter accepts an int>= 0. The default value is 0

Fixes #5001

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[rohitgr7]

you need to deprecate reload_dataloaders_every_epoch, assign its value to reload_dataloaders_every_n_epoch and raise a deprecation warning if it's set.

Also maybe rename reload_dataloaders_every_n_epoch to reload_dataloaders_every_n_epochs??

And ofcourse pls add a test too.

[tchaton]

LGTM ! Minor changes and a test.

[codecov]

Codecov Report

Merging #5043 (e173cee) into master (bca5adf) will decrease coverage by 5%.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master   #5043    +/-   ##
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- Coverage      92%     88%    -5%     
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  Files         213     213            
  Lines       13798   13809    +11     
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- Hits        12744   12132   -612     
- Misses       1054    1677   +623     

[sidhantls]

@rohitgr7 after looking at check_val_every_n_epoch I just went with reload_dataloaders_every_n_epoch. but sure, I can rename it to reload_dataloaders_every_n_epochs

[rohitgr7]

@rohitgr7 after looking at check_val_every_n_epoch I just went with reload_dataloaders_every_n_epoch. but sure, I can rename it to reload_dataloaders_every_n_epochs

ah.. I was just looking at these two arguments so though epochs might be better. https://github.com/PyTorchLightning/pytorch-lightning/blob/05f25f3a543dd06382feb7f19761e452af572288/pytorch_lightning/trainer/trainer.py#L111-L112

[pep8speaks]

Hello @sid-sundrani! Thanks for updating this PR.

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

Comment last updated at 2021-07-07 01:18:59 UTC

[sidhantls]

you need to deprecate reload_dataloaders_every_epoch, assign its value to reload_dataloaders_every_n_epoch and raise a deprecation warning if it's set.

@rohitgr7 the warning doesn't print for some reason if I use DeprecationWarning with rank_zero_warn

from pytorch_lightning.utilities import rank_zero_warn
# works, prints 
rank_zero_warn("Deprecation message..")
# doesnt print. there are a few examples of this usage 
rank_zero_warn("Deprecation message..", DeprecationWarning)

should I do the former?

[rohitgr7]

you need to deprecate reload_dataloaders_every_epoch, assign its value to reload_dataloaders_every_n_epoch and raise a deprecation warning if it's set.

@rohitgr7 the warning doesn't print for some reason if I use DeprecationWarning with rank_zero_warn

from pytorch_lightning.utilities import rank_zero_warn
# works, prints 
rank_zero_warn("Deprecation message..")
# doesnt print. there are a few examples of this usage 
rank_zero_warn("Deprecation message..", DeprecationWarning)

should I do the former?

Can you add the warning at the correct place where it should be and a failing test? Will check it. @sid-sundrani

[rohitgr7]

Let's make it an int only, no bool. Default to 0. since other similar parameters check_val_every_n_epoch, log_every_n_steps, ... doesn't accept a bool value.

[rohitgr7]

you also need to update the docs here: https://github.com/PyTorchLightning/pytorch-lightning/blob/master/pytorch_lightning/core/hooks.py

Also this test too: https://github.com/PyTorchLightning/pytorch-lightning/blob/eb9cb3c8017b1f207ac1d2c7168327fbe0b63cb5/tests/core/test_datamodules.py#L437

these docs here too: https://github.com/PyTorchLightning/pytorch-lightning/blob/master/docs/source/trainer.rst

[rohitgr7]

LGTM. I'm just wondering if someone sets limit_train/val/test_batches=0 should it even load the dataloaders at all??

[rohitgr7]

@sid-sundrani pls mark it as ready for review if it's ready.

[edenlightning]

@sid-sundrani any chance you can rebase and address final comments? we would love to finally merge!