Fix Bug: group_rewards Un-assigned value

[shiweijiezero]

Description

Fix Bug: group_rewards Un-assigned value

Checklist

Please check the following items before code is ready to be reviewed.

• Code has passed all tests
• Docstrings have been added/updated in Google Style
• Documentation has been updated
• Code is ready for review

[gemini-code-assist]

Summary of Changes

Hello @shiweijiezero, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request resolves a potential runtime error in the calculate_group_advantage function within the OPMD advantage calculation module. By relocating the initialization of the group_rewards tensor, the change ensures that the variable is always assigned before any conditional logic that might otherwise leave it undefined, thus enhancing the robustness and stability of the advantage computation.

Highlights

• Bug Fix: Addressed a bug in the calculate_group_advantage function where the group_rewards variable could be unassigned if the exps list contained only one experience. The initialization of group_rewards has been moved to ensure it is always defined.

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[gemini-code-assist]

Code Review

This pull request correctly fixes an UnboundLocalError that occurred when len(exps) was 1 by moving the initialization of group_rewards to before the conditional check. The fix is correct and addresses the bug. I've added one suggestion for a minor refactoring to improve efficiency and avoid a redundant calculation. Overall, good catch and fix!