Paper:
Deploying machine learning systems in the real world requires both high accuracy on clean data and robustness to naturally occurring corruptions. While architectural advances have led to improved accuracy, building robust models remains challenging, involving major changes in training procedure and datasets. Prior work has argued that there is an inherent trade-off between robustness and accuracy, as exemplified by standard data augmentation techniques such as Cutout, which improves clean accuracy but not robustness, and additive Gaussian noise, which improves robustness but hurts accuracy. We introduce Patch Gaussian, a simple augmentation scheme that adds noise to randomly selected patches in an input image. Models trained with Patch Gaussian achieve state of the art on the CIFAR-10 and ImageNet Common Corruptions benchmarks while also maintaining accuracy on clean data. We find that this augmentation leads to reduced sensitivity to high frequency noise (similar to Gaussian) while retaining the ability to take advantage of relevant high frequency information in the image (similar to Cutout). We show it can be used in conjunction with other regularization methods and data augmentation policies such as AutoAugment. Finally, we find that the idea of restricting perturbations to patches can also be useful in the context of adversarial learning, yielding models without the loss in accuracy that is found with unconstrained adversarial training.

Review:
This paper proposes a data augmentation method that interpolates between two existing methods (Cutout and Gaussian), for training robust models towards Gaussian and naturally occurring corruptions. The method is shown to improve robustness without sacrificing accuracy on clean data.
Pros:
The proposed method, despite being simple, seems to empirically work well in terms of the mCE criterion evaluated in the experiments. This does support the authors’ claim that current methods haven’t reached the robustness/accuracy tradeoff boundary yet.
Cons:
I’m a bit concerned about the significance of the work though. The method is a straight-forward combination of existing methods, so methodologically the novelty is kind of limited. Hence, I’m expecting more insights from the analysis of the results, to gain more understanding of why it works so well. However, the presentation of the experiments just seems to aim for the best numbers one can get (I’m not certain how significant the numbers are to this field though). A few examples/pictures of success cases (when the method works) and failure cases (when the method doesn’t work), may help readers (I’m not an expert) to better understand the approach and get more intuitions? The frequency analysis seems quite intuitive. It’s obvious that Gaussian filter blocks high-frequency components, and Cutout keeps some original parts of the image which allow high-freq details to be captured. But, considering CIFAR image size is only 32x32, a patch of size 25 is quite large, how much is the method different from plain whole image Gaussian then?