# An Ensemble of Epoch-wise Empirical Bayes for Few-shot Learning

## TL;DR

This paper introduces E3BM, a meta-learned ensemble of epoch-wise empirical Bayes models, to improve robustness and efficiency in few-shot learning across multiple benchmarks.

## Contribution

It proposes a novel meta-learning approach with four hyperprior learners for epoch-wise ensembling in few-shot tasks, achieving top performance.

## Key findings

- Top performance on miniImageNet, tieredImageNet, and FC100.
- Epoch-dependent transductive hyperprior yields best results.
- Both epoch-wise ensembling and empirical methods enhance robustness.

## Abstract

Few-shot learning aims to train efficient predictive models with a few examples. The lack of training data leads to poor models that perform high-variance or low-confidence predictions. In this paper, we propose to meta-learn the ensemble of epoch-wise empirical Bayes models (E3BM) to achieve robust predictions. "Epoch-wise" means that each training epoch has a Bayes model whose parameters are specifically learned and deployed. "Empirical" means that the hyperparameters, e.g., used for learning and ensembling the epoch-wise models, are generated by hyperprior learners conditional on task-specific data. We introduce four kinds of hyperprior learners by considering inductive vs. transductive, and epoch-dependent vs. epoch-independent, in the paradigm of meta-learning. We conduct extensive experiments for five-class few-shot tasks on three challenging benchmarks: miniImageNet, tieredImageNet, and FC100, and achieve top performance using the epoch-dependent transductive hyperprior learner, which captures the richest information. Our ablation study shows that both "epoch-wise ensemble" and "empirical" encourage high efficiency and robustness in the model performance.