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arXiv 2605.29495cs.LG

面向持续监督微调的在策略重放

On-Policy Replay for Continual Supervised Fine-Tuning

Tsinghua University(清华大学);Alibaba Group(阿里巴巴集团)

Yan Chen, Taojie Zhu, Meng Zhang, Xin Chen, Jiaqi Huang, Dongyang Xu, Yizhi Wang

AI总结:

提出在策略重放(OPR)方法,通过重放模型自身生成的高质量响应来缓解持续监督微调中的灾难性遗忘,在多个大语言模型上显著降低遗忘。

摘要:

持续监督微调(SFT)是将大型语言模型(LLMs)适配到连续下游任务的事实标准,但它会遭受早期能力的灾难性遗忘。最近的研究表明,在策略信号——在模型自身输出上训练——比离策略监督更可靠地减少遗忘。现有的在策略方法通过新的训练目标(例如,带有教师副本的自蒸馏损失)路由该信号,从而继承了额外的前向传播、调度敏感性和来自教师的风格漂移。我们改为通过训练数据源路由在策略信号。我们的方法,在策略重放(OPR),在少量历史提示上展开最新检查点,通过任务奖励过滤生成结果,并将幸存(提示,模型响应)对作为普通SFT示例重放。没有教师,没有辅助损失,也没有即时蒸馏。在三个7-8B指令微调骨干(Qwen2.5-7B-Instruct、Qwen3-8B、Llama3.1-8B-Instruct)上,在TRACE持续学习基准测试中,OPR一致地减少了遗忘;在最尖锐的压力测试(Qwen2.5-7B-Instruct,顺序SFT BWT -13.93)中,OPR在10%重放预算下将BWT提升至-0.65,在1%预算下提升至-2.29——与调优的普通重放基线相比,|BWT|减少了46%,在所有三个骨干上观察到42-46%的减少。我们给出了一个KL收缩解释,将OPR和先前的在策略蒸馏方法置于单一轴上,并提出了一个反直觉的发现,解释了为什么普通重放已经是一个强基线:低分重放一致地比普通重放更差,表明OPR中的有效成分是在策略分布,而不是单独的响应质量。我们的代码可在https://github.com/Yancey2024/OnPolicyReplay获取。

英文摘要:

Continual supervised fine-tuning (SFT) is the de facto recipe for adapting large language models (LLMs) to a stream of downstream tasks, but it suffers from catastrophic forgetting of earlier capabilities. Recent work shows that on-policy signals -- training on the model's own outputs -- reduce forgetting more reliably than off-policy supervision. Existing on-policy methods route this signal through a new training objective (e.g., self-distillation losses with a teacher copy), inheriting an extra forward pass, schedule sensitivity, and stylistic drift from the teacher.We instead route the on-policy signal through the training data source. Our method, On-Policy Replay (OPR), rolls out the most recent checkpoint on a small budget of historical prompts, filters the generations by a task reward, and replays the surviving (prompt, model response) pairs as ordinary SFT examples. There is no teacher, no auxiliary loss, and no on-the-fly distillation. Across three 7--8B instruction-tuned backbones (Qwen2.5-7B-Instruct, Qwen3-8B, Llama3.1-8B-Instruct) on the TRACE continual-learning benchmark, OPR consistently reduces forgetting; on the sharpest stress test (Qwen2.5-7B-Instruct, Sequential SFT BWT -13.93), OPR lifts BWT to -0.65 at a 10% replay budget and to -2.29 at a 1% budget -- a 46% reduction in |BWT| over a tuned Vanilla Replay baseline, with 42--46% reductions observed across all three backbones. We give a KL-shrinkage interpretation that places OPR and prior on-policy distillation methods on a single axis, and we present a counterintuitive finding that explains why Vanilla Replay is already a strong baseline: low-score replay is uniformly worse than Vanilla Replay, demonstrating that the active ingredient in OPR is the on-policy distribution, not the response quality alone.Our code is available at https://github.com/Yancey2024/OnPolicyReplay.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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