Add option to not flatten config in WandbLogger.log_hyperparams

[zephyap]

🚀 Feature

Reopening issue #9264: Make the config flattening that happens in WandbLogger.log_hyperparams optional.

Motivation

Similar to the original issue, flattening the config makes it harder to re-use later.

From the original issue:

Wandb support nested config by default. Furthermore, by flattening the configuration it makes it more difficult to load an experiment from a wandb run – instead of taking the config directly from the run, you have to un-flatten it first (or really, not use log_hyperparams and instead do it manually).

Pitch

Add flatten: bool = True as a kwarg in log_hyperparams.

Alternatives

• Creating custom logger subclasses that do not flatten the config
  • Feels hacky, does not keep up well with new loggers being added.
• Writing our own function to unflatten the config
  • Seems like a workable alternative, albeit a roundabout one. It adds one more moving piece to the system in order for configs to be reused, so my preference would still be to not flatten it at all, if possible.

cc @Borda @awaelchli @morganmcg1 @borisdayma @scottire @parambharat

[dsuess]

This would be a great feature to add. Note that since #2458, Wandb has added support to properly display non-flattened configs in their UI. Since we often don't control where log_hyperparams gets called, I think an init-argument to toggle this behaviour would be handy.

[rohitgr7]

I think if it supports nested config, we shouldn't flatten it at all.

[mattcleigh]

Inspecting the hyperparameters on the wandb website is certainly easier without flattening, as it is presented as a collapsible dropdown list. I would definitely support adding in a flatten_hyperparams argument in the wandb logger init, or just removing the flattening step all together.

[stale]

This issue has been automatically marked as stale because it hasn't had any recent activity. This issue will be closed in 7 days if no further activity occurs. Thank you for your contributions - the Lightning Team!

[zephyap]

I'm still interested in this! But I understand if the team doesn't have time to work on it

[awaelchli]

Another user who discovered this: #17559
Anyone here wants to send a PR to update the parameter sanitization not to flatten the dicts?