Abstract
On-policy distillation (OPD) has demonstrated two important capabilities in language models: compressing large teachers into smaller students and merging expert models into a single model. Existing diffusion OPD, however, mostly focus on the latter, with teachers and students sharing the same backbone and scale. We investigate large-to-small diffusion opd from large teachers to a small student and find that the standard recipe fails. To find the underlying cause, we propose Fixed-State KL, an effective and fair way to measure the distribution gap between student and teacher during OPD training for diffusion models. We are the first to clarify why large-to-small OPD is challenging for diffusion models: a smaller student struggles to perfectly match the distribution of a larger teacher, while classifier-free guidance can accumulate and amplify the distributional discrepancies between the student's conditional and unconditional branches and those of the teacher. To solve this problem, we propose GFD-OPD, a simple yet effective method that reduces the student-teacher gap while avoiding the error amplification of the CFG composition. Across numerous experiments, GFD outperforms previous baselines in both training efficiency and final performance, achieving state-of-the-art results on all benchmarks.
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Publication details
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Cite this article
APA 7
Zhang, Z., Teng, J., Wu, W., Yang, Z., Xu, J., Zheng, W., Tang, J., Guo, D., & Wang, M. (2026). GFD-OPD: Guidance-Folded On-Policy Distillation of Diffusion Models Across Scales. https://omanscience.com/en/articles/gfd-opd-guidance-folded-on-policy-distillation-of-diffusion-models-across-scales
MLA 9
Zhang, Zhenxing, et al. "GFD-OPD: Guidance-Folded On-Policy Distillation of Diffusion Models Across Scales." https://omanscience.com/en/articles/gfd-opd-guidance-folded-on-policy-distillation-of-diffusion-models-across-scales.
Chicago (author–date)
Zhang, Zhenxing, Jiayan Teng, Wenxu Wu, Zhuoyi Yang, Jiazheng Xu, Wendi Zheng, Jie Tang, Dan Guo, and Meng Wang. 2026. "GFD-OPD: Guidance-Folded On-Policy Distillation of Diffusion Models Across Scales." https://omanscience.com/en/articles/gfd-opd-guidance-folded-on-policy-distillation-of-diffusion-models-across-scales.
Harvard
Zhang, Z., Teng, J., Wu, W., Yang, Z., Xu, J., Zheng, W., Tang, J., Guo, D. and Wang, M. (2026) 'GFD-OPD: Guidance-Folded On-Policy Distillation of Diffusion Models Across Scales', Available at: https://omanscience.com/en/articles/gfd-opd-guidance-folded-on-policy-distillation-of-diffusion-models-across-scales.
Vancouver
Zhang Z, Teng J, Wu W, Yang Z, Xu J, Zheng W, et al. GFD-OPD: Guidance-Folded On-Policy Distillation of Diffusion Models Across Scales. https://omanscience.com/en/articles/gfd-opd-guidance-folded-on-policy-distillation-of-diffusion-models-across-scales
IEEE
Z. Zhang, J. Teng, W. Wu, Z. Yang, J. Xu, W. Zheng, J. Tang, D. Guo, and M. Wang, "GFD-OPD: Guidance-Folded On-Policy Distillation of Diffusion Models Across Scales," https://omanscience.com/en/articles/gfd-opd-guidance-folded-on-policy-distillation-of-diffusion-models-across-scales.