Contextual Squeeze-and-Excitation

Massimiliano Patacchiola, John F Bronskill, Aliaksandra Shysheya, Katja Hofmann, Sebastian Nowozin, Richard E Turner

Keywords: few-shot learning, image classification, meta-learning

TL;DR: A new efficient adaptive block for transfer learning across datasets in few-shot image classification

Abstract: Several applications require effective knowledge transfer across tasks in the low-data regime. For instance in personalization a pretrained system is adapted by learning on small amounts of labeled data belonging to a specific user (context). This setting requires high accuracy under low computational complexity, meaning low memory footprint in terms of parameters storage and adaptation cost. Meta-learning methods based on Feature-wise Linear Modulation generators (FiLM) satisfy these constraints as they can adapt a backbone without expensive fine-tuning. However, there has been limited research on viable alternatives to FiLM generators. In this paper we focus on this area of research and propose a new adaptive block called Contextual Squeeze-and-Excitation (CaSE). CaSE is more efficient than FiLM generators for a variety of reasons: it does not require a separate set encoder, has fewer learnable parameters, and only uses a scale vector (no shift) to modulate activations. We empirically show that CaSE is able to outperform FiLM generators in terms of parameter efficiency (a 75% reduction in the number of adaptation parameters) and classification accuracy (a 1.5% average improvement on the 26 datasets of the VTAB+MD benchmark).