Fine-grained visual categorization (FGVC) is a challenging task due to
similar visual appearances between various species. Previous studies always
implicitly assume that the training and test data have the same underlying
distributions, and that features extracted by modern backbone architectures
remain discriminative and generalize well to unseen test data. However, we
empirically justify that these conditions are not always true on benchmark
datasets. To this end, we combine the merits of invariant risk minimization
(IRM) and information bottleneck (IB) principle to learn invariant and minimum
sufficient (IMS) representations for FGVC, such that the overall model can
always discover the most succinct and consistent fine-grained features. We
apply the matrix-based R{\'e}nyi's $\alpha$-order entropy to simplify and
stabilize the training of IB; we also design a ``soft" environment partition
scheme to make IRM applicable to FGVC task. To the best of our knowledge, we
are the first to address the problem of FGVC from a generalization perspective
and develop a new information-theoretic solution accordingly. Extensive
experiments demonstrate the consistent performance gain offered by our IMS.

通过适用于不变风险最小化和信息瓶颈原理的方法，从泛化的角度解决细粒度视觉分类问题，并应用 Rényi 的 α- 阶熵和软环境分割方案来训练模型，以学习不变和最小化的表示。实验证实了该方案在细粒度视觉分类中能显著提高性能。