做LLM预训练或知识蒸馏的团队，这篇论文直接挑战了“教师越强越好”的默认假设，看完可能会重新设计你的蒸馏策略，值得细读。
这篇论文挑战了知识蒸馏中“强教师才能教出好学生”的传统观念。研究发现，在LLM预训练阶段，即使使用较小或训练不足的弱教师模型，通过合理混合语言建模和蒸馏损失，也能提升更大的学生模型。相反，更强的教师（更多参数或更多训练数据）可能导致蒸馏收益饱和甚至下降。此外，蒸馏在提升泛化能力（如分布外和下游任务表现）方面比在领域内拟合更有效。这些结果颠覆了蒸馏预训练必须依赖强教师的普遍认知。
Strong Teacher Not Needed? On Distillation in LLM Pretraining
Knowledge distillation generally assumes a strong-to-weak relationship where stronger teachers yield better students. In this work, we examine this assumption about distillation in large language model pretraining. By varying architecture sizes and training token budgets, we create strong-to-weak, same-level, and weak-to-strong teacher-student relationships, and study distillation's effectiveness under each. We find that the teacher need not be strong: with proper mixing of the language modeling and knowledge distillation losses, even small and undertrained teachers improve larger students. At the same time, a stronger teacher is not always better: pushing the teacher further, through more parameters or more training tokens, can saturate or even reverse the distillation gains. We further observe that distillation improves generalization (out-of-distribution and downstream performance) more readily than in-domain fitting. Together, these results challenge the common belief that distillation pretraining always requires a strong teacher.