Towards Enabling Meta-Learning from Target Models

TL;DR

This paper explores a novel evaluation protocol in meta-learning that compares task-specific solvers to target models, showing that even with limited target models, classic algorithms can be significantly improved in few-shot learning tasks.

Contribution

It introduces the $ ext{S/T}$ protocol for meta-learning evaluation, demonstrating its practical benefits and effectiveness through knowledge distillation with limited target models.

Findings

The $ ext{S/T}$ protocol provides more informative supervision than traditional methods.

Using a small ratio of target models can substantially improve meta-learning performance.

Empirical results in few-shot learning validate the effectiveness of the proposed approach.

Abstract

Meta-learning can extract an inductive bias from previous learning experience and assist the training of new tasks. It is often realized through optimizing a meta-model with the evaluation loss of task-specific solvers. Most existing algorithms sample non-overlapping $\mathit{support}$ sets and $\mathit{query}$ sets to train and evaluate the solvers respectively due to simplicity ($\mathcal{S}$/$\mathcal{Q}$ protocol). Different from $\mathcal{S}$/$\mathcal{Q}$ protocol, we can also evaluate a task-specific solver by comparing it to a target model $\mathcal{T}$, which is the optimal model for this task or a model that behaves well enough on this task ($\mathcal{S}$/$\mathcal{T}$ protocol). Although being short of research, $\mathcal{S}$/$\mathcal{T}$ protocol has unique advantages such as offering more informative supervision, but it is computationally expensive. This paper looks into this special evaluation method and takes a step towards putting it into practice. We find that with a small ratio of tasks armed with target models, classic meta-learning algorithms can be improved a lot without consuming many resources. We empirically verify the effectiveness of $\mathcal{S}$/$\mathcal{T}$ protocol in a typical application of meta-learning, $\mathit{i.e.}$, few-shot learning. In detail, after constructing target models by fine-tuning the pre-trained network on those hard tasks, we match the task-specific solvers and target models via knowledge distillation.