Fix logging inconsistency: unify metrics logging to use global_steps

[joaobenedetmachado]

Problem

Logging for metrics returned by loss functions via aux was at a _iter_steps level,
whereas other metrics were logged at a global_steps level. The progress bar for
GRPO/PPO was at a _iter_steps level. This inconsistency made it confusing for
users to pass max_steps at a _iter_steps level, and not at global_steps level.

Solution

Unified logging to use global_steps consistently across all components:

• Add global_steps property to PeftTrainer (returns train_steps for compatibility)
• Update DPO trainer to use global_steps for aux metrics logging
• Update progress bar to use global_steps for initial_steps
• Ensures consistent step counting across all RL algorithms
• Resolves confusion about max_steps parameter interpretation

Files Changed

• tunix/sft/peft_trainer.py - Added global_steps property and updated progress bar
• tunix/sft/dpo/dpo_trainer.py - Updated logging methods to use global_steps

Testing

• All code verification tests pass
• Backward compatibility maintained (global_steps = train_steps)
• Demo notebook available in Colab

Resolves #390

Colab Notebook
https://colab.research.google.com/drive/1hMelDYWB5w3v3W6anOChPDFXruMCbjlY?usp=sharing

Checklist

• I have added all the necessary unit tests for my change.
• I have verified that my change does not break existing code and all unit tests pass.
• I have added all appropriate doc-strings/documentation.
• My PR is based on the latest changes of the main branch (if unsure, rebase the code).
• I have signed the Contributor License Agreement.
• I have followed Contribution Guidelines.

[wang2yn84]

Thank you for your PR! We recently noticed there are some issue in DPO metrics logging and it's fixed by: ac07cfd. So the DPO trainer part is no longer valid and necessary. But we can still land the peft trainer part. Can you rebase?

[joaobenedetmachado]

Thanks for the feedback! I’ve rebased the branch with the latest main and removed the DPO-related changes since they were already addressed in ac07cfd.
The PR now only includes the PeftTrainer updates to unify logging with global_steps.
All tests pass and everything is ready for review. 👍