Step size for snow and fog attacks

[hugemicrobe]

In the paper, it's mentioned that step_size = bound / sqrt(iterations). But based on the output files, e.g.

analysis/calibrations/imagenet-100/fog.out
analysis/calibrations/imagenet-100/snow.out

The step sizes seem to be a constant 0.002236 no matter what bound is used. Are these the expected setup?

[yi-sun]

Thanks for your interest in our work. Yes, this was an oversight in our paper. For Fog, Gabor, and Snow, the step size should be sqrt(0.001 / steps), since distortion size is controlled differently for these attacks. In particular, a perturbation is generated by optimizing parameters in a latent space of fixed size, scaled by distortion size epsilon, and then added to the original image. This means that the step_size should be independent of epsilon in this case. We have corrected this in the updated version of our paper at: https://arxiv.org/abs/1908.08016.