DeepOffer

Explain DPO, why it displaced PPO-based RLHF at many labs, and when online RL is still preferable.

ML TheoryReported interview question
Reported in public interview compilations — Hugging Face, Scale AI

RLHF trains a preference or reward model from comparisons, then optimizes the policy while constraining drift from a reference model, often with a KL term. Reward misspecification, overoptimization, and preference bias require held-out human evaluation.

Use equations or tensor shapes where they clarify the claim, then name an experiment or ablation that would distinguish competing explanations.

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