How to let lightning store hyperparameters in checkpoint when working with Hydra configs?

[mariomeissner]

In my personal hydra lightning setup, I am passing certain instantiated objects as parameters to my model (e.g. a loss function). It's convenient because I can say _target_: torch.nn.CrossentropyLoss in the config file.

The problem is that lightning will fail to store the hyperparameters in the checkpoint file because it is not pickable. How can I make this work? I ask here because I assume that this problem had to be somehow overcome here too, but a quick look at the source code didn't give me the answer yet.

Interestingly, inside the lightning checkpoint saving code, there is some logic trying to identify if we are working with OmegaConf containers, but it's still not straightforward for me to adapt my code to this situation.

[Borda]

@SeanNaren, mind haveing a look? :)

[mariomeissner]

I personally solved this one by storing object references as classpath strings instead. Not ideal, as it's fancier to pass a hydra-initialized object rather than a string...

[mariomeissner]

Either way, it seems wanted to move over to Lightning CLI, is that still a plan in the works? ^^