Why GRPO: The SFT vs. RFT vs. RLHF Decision Tree
~15 min read
GRPO exists to solve reasoning-heavy tasks where correctness is verifiable — the book's own decision tree shows exactly when GRPO-style RFT is the right call versus SFT or RLHF.
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Key points
- •GRPO answers a specific branch of a larger decision tree: no labeled data, but the task IS verifiable -> RFT (GRPO is a leading RFT method)
- •No labeled data, task NOT verifiable -> RLHF instead (needs human preference signals)
- •Labeled data exists: large dataset -> SFT; tiny dataset where reasoning helps -> RFT/GRPO
- •SFT trains on static data and often memorizes answers; RFT is online, exploring outputs and learning from a reward signal
- •GRPO uses deterministic reward functions to check correctness automatically, eliminating the need for labeled data entirely