It Takes Two: Your GRPO Is Secretly DPO. - Yihong Wu; Liheng Ma; Lei Ding; Muzhi Li 001; Xinyu Wang; Kejia Chen; Zhan Su 002; Zhanguang Zhang; Chenyang Huang; Yingxue Zhang 001; Mark Coates; Jian-Yun Nie (CoRR, 2025)