测试近1000个公开LoRA,发现自适应合并效果有限,可能只是正则化起作用。
The Appeal and Reality of Recycling LoRAs with Adaptive Merging
- 从近1000个用户贡献的LoRA中筛选并自适应合并
- 合并后性能优于基线模型,但不如直接训练新LoRA
- 随机初始化参数的LoRA也能达到相似效果,暗示正则化是主因
针对开源预训练模型微调产生的大量LoRA模块,现有自适应合并方法通常从池中选择部分LoRA,并基于特定任务数据集调整合并系数。然而,此前工作未尝试从Hugging Face Hub等平台回收“野生”LoRA。本文基于近1000个由Llama 3.1 8B-Instruct训练的用户贡献LoRA,评估多种自适应与非自适应合并方法,包括一项通过广泛搜索设计的新方法。实验表明,自适应合并虽能提升基线性能,但相较于在相同数据上直接训练新LoRA,优势有限。进一步发现,被合并的LoRA具体选择影响极小,甚至随机初始化参数的LoRA也表现相当。这提示自适应合并可能主要依赖某种正则化效应而非跨任务正向迁移。我们验证了当池中存在高度相关的LoRA时,正向迁移仍可实现。相关模型检查点与代码已公开。
原文摘要 · Abstract (English)
The widespread availability of fine-tuned LoRA modules for open pre-trained models has led to an interest in methods that can adaptively merge LoRAs to improve performance. These methods typically include some way of selecting LoRAs from a pool and tune merging coefficients based on a task-specific dataset. While adaptive merging methods have demonstrated improvements in some settings, no past work has attempted to recycle LoRAs found "in the wild" on model repositories like the Hugging Face Hub. To address this gap, we consider recycling from a pool of nearly 1,000 user-contributed LoRAs trained from the Llama 3.1 8B-Instruct language model. Our empirical study includes a range of adaptive and non-adaptive merging methods in addition to a new method designed via a wide search over the methodological design space. We demonstrate that adaptive merging methods can improve performance over the base model but provide limited benefit over training a new LoRA on the same data used to set merging coefficients. We additionally find not only that the specific choice of LoRAs to merge has little importance, but that using LoRAs with randomly initialized parameter values yields similar performance. This raises the possibility that adaptive merging from recycled LoRAs primarily works via some kind of regularization effect, rather than by enabling positive cross-task transfer. To better understand why past work has proven successful, we confirm that positive transfer is indeed possible when there are highly relevant LoRAs in the pool. We release the model checkpoints and code online.
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