Therepresentssymbol prompt-basedindicates adaptermethods,-based source63domain data may lead to overfitting and denotes partially fine-tuned methods, and de-poor63generalization to unseen domains.

The generalization ability of deep learning has been extensively studied in supervised settings, yet it remains less explored in unsupervised scenarios. Recently, the Unsupervised Domain Generalization (UDG) task has been proposed to enhance the generalization of models trained with prevalent unsupervised learning techniques, such as Self-Supervised Learning (SSL). UDG confronts the challenge of distinguishing semantics from variations without category labels. Although some recent methods have employed domain labels to tackle this issue, such domain labels are often unavailable in real-world contexts. In this paper, we address these limitations by formalizing UDG as the task of learning a Minimal Sufficient Semantic Representation: a representation that (i) preserves all semantic information shared across augmented views (sufficiency), and (ii) maximally removes information irrelevant to semantics (minimality). We theoretically ground these objectives from the perspective of information theory, demonstrating that optimizing representations to achieve sufficiency and minimality directly reduces out-of-distribution risk. Practically, we implement this optimization through Minimal-Sufficient UDG (MSUDG), a learnable model by integrating (a) an InfoNCE-based objective to achieve sufficiency; (b) two complementary components to promote minimality: a novel semantic-variation disentanglement loss and a reconstruction-based mechanism for capturing adequate variation. Empirically, MS-UDG sets a new state-of-the-art on popular unsupervised domain-generalization benchmarks, consistently outperforming existing SSL and UDG methods, without category or domain labels during representation learning.

Then, MP A denoises the learned prompts through an auto-encoding process and aligns them by maximizing the agreement of all the reconstructed prompts.

Even in large language models, negative transfer problems may still exist.

Even in large language models, negative transfer problems may still exist.

Recall measures the fraction ofcommon samples that are retrievedascorrect common class, while specificity measures thefraction ofprivatesamples thatarenotretrieved. Fig. S1(b) shows the sensitivity ofγ, where γ is the rough boundary for splitting positive and negative in adaptive filling. For the cosine similarity of two ℓ2-normalized features, the similarity value is limited from 1to1, where higher value indicates higher similarity. Suchself-supervisedlearning methods encourage the consistency between two augmentations of one image. The display images for source prototypes are chosen by finding the nearest source instance of the prototype.