Title: Generative Adversarial Neural Architecture Search with Importance Sampling. Abstract: Despite the empirical success of neural architecture search (NAS) in deep learning applications, the optimality, reproducibility and cost of NAS schemes remain hard to assess. The variation in search spaces adopted has further affected a fair comparison between search strategies. In this paper, we focus on search strategies in NAS and propose Generative Adversarial NAS (GA-NAS), promoting stable and reproducible neural architecture search. GA-NAS is theoretically inspired by importance sampling for rare event simulation, and iteratively refits a generator to previously discovered top architectures, thus increasingly focusing on important parts of the search space. We propose an efficient adversarial learning approach in GA-NAS, where the generator is not trained based on a large number of observations on architecture performance, but based on the relative prediction made by a discriminator, thus significantly reducing the number of evaluations required.
Extensive experiments show that GA-NAS beats the best published results under several cases on the public NAS benchmarks including NAS-Bench-101, NAS-Bench-201, and NAS-Bench-301. We further show that GA-NAS can handle ad-hoc search constraints and search spaces. GA-NAS can find new architectures that enhance EfficientNet and ProxylessNAS in  terms of ImageNet Top-1 accuracy and/or the number of parameters by searching in their original search spaces.