DCNAS: Densely Connected Neural Architecture Search for Semantic Image Segmentation

TL;DR

DCNAS introduces a densely connected neural architecture search framework that directly optimizes network structures for semantic segmentation on large datasets, achieving state-of-the-art results.

Contribution

It proposes a novel densely connected search space and a fusion module to efficiently search for optimal multi-scale network architectures for semantic segmentation.

Findings

Achieves 84.3% mIoU on Cityscapes

Achieves 86.9% mIoU on PASCAL VOC 2012

Retains high performance on ADE20K and Pascal Context

Abstract

Neural Architecture Search (NAS) has shown great potentials in automatically designing scalable network architectures for dense image predictions. However, existing NAS algorithms usually compromise on restricted search space and search on proxy task to meet the achievable computational demands. To allow as wide as possible network architectures and avoid the gap between target and proxy dataset, we propose a Densely Connected NAS (DCNAS) framework, which directly searches the optimal network structures for the multi-scale representations of visual information, over a large-scale target dataset. Specifically, by connecting cells with each other using learnable weights, we introduce a densely connected search space to cover an abundance of mainstream network designs. Moreover, by combining both path-level and channel-level sampling strategies, we design a fusion module to reduce the memory consumption of ample search space. We demonstrate that the architecture obtained from our DCNAS algorithm achieves state-of-the-art performances on public semantic image segmentation benchmarks, including 84.3% on Cityscapes, and 86.9% on PASCAL VOC 2012. We also retain leading performances when evaluating the architecture on the more challenging ADE20K and Pascal Context dataset.