[megatron] fix train_iters

[Jintao-Huang]

No description provided.

[gemini-code-assist]

Summary of Changes

Hello @Jintao-Huang, 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 introduces a targeted fix to the Megatron training setup by adjusting how the num_generations parameter is determined. The modification ensures that this parameter is correctly configured based on the specific type of Reinforcement Learning from Human Feedback (RLHF) being utilized, thereby preventing miscalculations in training iterations and enhancing the robustness of the training process.

Highlights

• Refined num_generations calculation: The logic for determining num_generations has been updated to be conditional on args.rlhf_type == 'grpo', ensuring it is only applied when the 'grpo' type of Reinforcement Learning from Human Feedback (RLHF) is active.
• Improved train_iters accuracy: This change directly addresses a potential inaccuracy in train_iters calculation by ensuring num_generations is correctly set for specific training scenarios, particularly within the Megatron framework.

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[gemini-code-assist]

Code Review

This pull request aims to correct the calculation of train_iters by ensuring num_generations is only applied for GRPO training. However, the current change introduces a critical issue where non-RLHF training runs (like SFT) will crash with an AttributeError because the rlhf_type attribute is not always present on the arguments object. I have provided a suggestion to fix this by safely accessing the attribute.

[gemini-code-assist]

The direct access to args.rlhf_type will cause an AttributeError for training configurations that do not define this attribute, such as SFT. This will lead to a crash in non-RLHF training scenarios.

To prevent this, you should use getattr to safely access the rlhf_type attribute with a default value.

Suggested change

	num_generations = args.num_generations if args.rlhf_type == 'grpo' else 1
	num_generations = args.num_generations if getattr(args, 'rlhf_type', None) == 'grpo' else 1