GRPO & Verifiable Rewards
February 1, 2025
GRPO (Group Relative Policy Optimization) is an RL technique originally proposed in the DeepSeekMathpaper. Instead of using a full-blown value network like PPO does, GRPO samples a group of completions for a given prompt and then computes a relative (normalized) reward for each output. The rewards are “verifiable” because they come from checking the final answer against ground truth and confirming. E.g. does the response follow the expected format (i.e. a <think>…</think> block for reasoning and an <answer>…</answer> block for the solution) and is the answer accurate against a predetermined fact. Not every problem fits this model, but there are a bunch that do, including math reasoning with the GSM8Kdataset of grade-school math word problems. These look like this:
