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⚡ LLMsID: grpo

Group Relative Policy Optimization

GRPO 相对策略优化
🎯Core Definition
GRPO (Group Relative Policy Optimization) is the RL alignment method used by DeepSeek-R1. Core idea: sample GG responses per prompt and compute advantage from group-relative scores — subtract the group mean, divide by the group std — eliminating the value/critic network entirely; advantage depends only on within-group ranking, not absolute scores.
💡Use Cases
RL for large reasoning models (math, code — tasks with verifiable rewards); standard in DeepSeek-R1/V3, and suited to sparse-reward reasoning RL that needs exploration.
⚡Key Problems Solved
PPO needs a value network the size of the policy, costing VRAM comparable to training another large model; GRPO replaces it with group statistics, cutting training memory substantially and resisting reward-scale drift by construction.
🎯Core Interview Exam Points
Fundamentals · Production Scenarios · Deep Dive
Core Def
Explain the core definition, underlying mechanism/math, and key principles of Group Relative Policy Optimization.
Use Cases
In production engineering, what are the primary use cases for Group Relative Policy Optimization and what core pain points does it solve?
🔥 High-Frequency Deep-Dive Questions
1
What's GRPO's key improvement over PPO, and why can it drop the critic?
2
How is GRPO's advantage computed? The group-relative normalization formula?
3
How does R1 combine GRPO with verifiable rewards (RLVR) for reasoning?
4
How does group size G affect training, and how is the KL penalty designed?
5
When would you choose GRPO vs DPO?
Updated 2026-08-11
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