  The efficient, automated search for well-performing neural architectures
(NAS) has drawn increasing attention in the recent past. Thereby, the
predominant research objective is to reduce the necessity of costly evaluations
of neural architectures while efficiently exploring large search spaces. To
this aim, surrogate models embed architectures in a latent space and predict
their performance, while generative models for neural architectures enable
optimization-based search within the latent space the generator draws from.
Both, surrogate and generative models, have the aim of facilitating
query-efficient search in a well-structured latent space. In this paper, we
further improve the trade-off between query-efficiency and promising
architecture generation by leveraging advantages from both, efficient surrogate
models and generative design. To this end, we propose a generative model,
paired with a surrogate predictor, that iteratively learns to generate samples
from increasingly promising latent subspaces. This approach leads to very
effective and efficient architecture search, while keeping the query amount
low. In addition, our approach allows in a straightforward manner to jointly
optimize for multiple objectives such as accuracy and hardware latency. We show
the benefit of this approach not only w.r.t. the optimization of architectures
for highest classification accuracy but also in the context of hardware
constraints and outperform state-of-the-art methods on several NAS benchmarks
for single and multiple objectives. We also achieve state-of-the-art
performance on ImageNet. The code is available at
http://github.com/jovitalukasik/AG-Net .
