Deep neural networks often exhibit poor performance on data that is unlikely under the train-time data distribution, for instance data affected by corruptions. Previous works demonstrate that test-time adaptation to data shift, for instance using entropy minimization, effectively improves performance on such shifted distributions. This paper focuses on the fully test-time adaptation setting, where only unlabeled data from the target distribution is required. This allows adapting arbitrary pretrained networks. Specifically, we propose a novel loss that improves test-time adaptation by addressing both premature convergence and instability of entropy minimization. This is achieved by replacing the entropy by a non-saturating surrogate and adding a diversity regularizer based on batch-wise entropy maximization that prevents convergence to trivial collapsed solutions. Moreover, we propose to prepend an input transformation module to the network that can partially undo test-time distribution shifts. Surprisingly, this preprocessing can be learned solely using the fully test-time adaptation loss in an end-to-end fashion without any target domain labels or source domain data. We show that our approach outperforms previous work in improving the robustness of publicly available pretrained image classifiers to common corruptions on such challenging benchmarks as ImageNet-C.

该论文研究深度神经网络在非训练时数据分布下表现不佳的问题，提出一种全测试时间适应的解决方案，通过使用替代熵和添加基于批次的熵最大化的多样性正则化器来解决熵最小化的早期收敛和不稳定性问题，并且可以通过在完全测试时间适应性损失中学习无需目标域标签或源域数据的输入变换模块，从而达到在ImageNet-C等挑战性基准测试中提高公共预训练图像分类器鲁棒性的效果。

通过置信度最大化和输入变换对分布偏移进行测试时间适应