09/13/2026
Reasoning models like DeepSeek-R1 lean on GRPO, Group Relative Policy Optimization, to do something PPO struggles with. It assigns credit across long reasoning chains without blowing up memory. The idea is clean. Generate several responses to the same prompt, then rank them against each other instead of against some absolute reward. No separate value network needed. Pair that with process rewards that grade individual reasoning steps and not just the final answer, and you get the step-change in reasoning we've watched land this year.