Ignite: Add W&B logger

[vfdev-5]

🚀 Feature

Add logger to W&B similarly to MLflow, Neptune...

[fdlm]

I might be able to help with this. What should the logger be able to log, at minimum, for the first version?

[vfdev-5]

@fdlm thanks ! Let's start with main wrapper and OutputHandler to log scalars.

[vfdev-5]

@fdlm feel free to ask if you need help to implement it.

[kai-tub]

I also thought about contributing to this feature, but due to time constraints and still having open issues (sry 😅 ) I decided not to, but I would like to put in my 2ct:

• Due to the high flexibility of wandb I would go for an implementation style like in ml-flow-logger
• A possible issue would be the different usages of the current step in wandb. Some people just log every step independently and log the epochs extra (flexible) and others log them with the epochs to combine the different logs to a single upload per epoch and to get nice default diagrams

What are your opinions @fdlm ? :)

[fdlm]

I agree, and I think the general logging framework of ignite allows for a very flexible solution. Basically, you can attach output handlers to engines at the desired Event, so you get to decide if you log after each step, or after each epoch. Additionally, you can decide which "step" the logs should be attached to by providing the corresponding global_step_transform function.

So I think it's easy to obtain the flexibility you suggest.

[vfdev-5]

@fdlm any updates on the PR ?

[fdlm]

Finalizing the tests, should have a PR ready later today or tomorrow.