Few-shot unsupervised domain adaptation (FS-UDA) utilizes few-shot labeled source domain data to realize effective classification in unlabeled target domain. However, current FS-UDA methods are still suffer from two issues: 1) the data from different domains can not be effectively aligned by few-shot labeled data due to the large domain gaps, 2) it is unstable and time-consuming to generalize to new FS-UDA tasks.To address this issue, we put forward a novel Efficient Meta Prompt Learning Framework for FS-UDA. Within this framework, we use pre-trained CLIP model as the feature learning base model. First, we design domain-shared prompt learning vectors composed of virtual tokens, which mainly learns the meta knowledge from a large number of meta tasks to mitigate domain gaps. Secondly, we also design a task-shared prompt learning network to adaptively learn specific prompt vectors for each task, which aims to realize fast adaptation and task generalization. Thirdly, we learn a task-specific cross-domain alignment projection and a task-specific classifier with closed-form solutions for each meta task, which can efficiently adapt the model to new tasks in one step. The whole learning process is formulated as a bilevel optimization problem, and a good initialization of model parameters is learned through meta-learning. Extensive experimental study demonstrates the promising performance of our framework on benchmark datasets. Our method has the large improvement of at least 15.4% on 5-way 1-shot and 8.7% on 5-way 5-shot, compared with the state-of-the-art methods. Also, the performance of our method on all the test tasks is more stable than the other methods.

一种新的高效元提示学习框架用于少样本无监督领域适应，通过设计领域共享的提示学习向量和任务共享的提示学习网络，实现了领域间的对齐和快速任务适应，并通过元学习得到良好的模型参数初始化，在基准数据集上展现出了有希望的性能提升和更稳定的表现。

EMPL: 一种高效的元提示学习框架用于少样本无监督领域自适应