Flash-GRPO: Efficient Alignment for Video Diffusion via One-Step Policy Optimization. - Xiaoxuan He; Siming Fu; Zeyue Xue; Weijie Wang; Ruizhe He; Yuming Li; Dacheng Yin; Shuai Dong; Haoyang Huang; Hongfa Wang; Nan Duan 001; Bohan Zhuang (CoRR, 2026)