(ICCV 2019) Progressive Differentiable Architecture Search:Bridging the Depth Gap between Search and Evaluation

Keyword [P-Darts]

Chen X, Xie L, Wu J, et al. Progressive Differentiable Architecture Search: Bridging the Depth Gap between Search and Evaluation[J]. arXiv preprint arXiv:1904.12760, 2019.

1. Overview

1.1. Motivation

1) There is a large gap between the architecture depths in search and evaluation scenarios.
2) Darts searchs in a shallow network and evaluates in a deeper one.
3) Darts lacks of stability and can be biased heavily towards skip-connect.

In this paper, it proposes P-Darts
1) the depth of searched architectures to grow gradually during the training procedure.
2) multiple search stages. 3 stages
3) reduced searching time (~7 hours on a single GPU)

1.2. Technique

1.2.1 Search Space Approximation

  • depth increases with candidate operations decreases
  • solve the problem of exponentially increasing

1.2.2 Search Space Regularization

  • operation (skip-connect) level dropout & control the appearance of skip-connection
  • solve the problem of instability

1.3. Dataset

1) CIFAR10
2) CIFAR100

2. P-Darts

2.1. Search Space Approximation

  • In final stage, keep two top-weighted non-zero operations

2.2. Search Space Regularization

observe that information prefers to flow through skip-connect instead of other
1) insert operation level dropout after each skip-connect
gradually decay the Dropout rate during the training process in each search stage
2) control the number of skip-connect to be M in final stage
if searched number of skip-connect is not M, choose top-M operation and set other to 0, redo cell construction. And repeate.

3. Experiments

3.1. Details

  • 3 stages. 5,11,17 cells; 8,5,3 operation; 0.0, 0.4, 0.7 on CIFAR10; 0.1, 0.2, 0.3 on CIFAR100
  • M = 2 at most

3.2. Search Results

3.3. Comparison