Structure Inducing Pre-Training

TL;DR

This paper investigates how pre-training methods induce relational structure in latent spaces, providing a framework to understand, analyze, and improve pre-training for diverse domains and tasks.

Contribution

It introduces a comprehensive framework for analyzing relational structure in pre-training, linking inductive biases to fine-tuning performance, and proposes new methods validated through extensive experiments.

Findings

Relational structure in latent spaces correlates with fine-tuning success.

The proposed framework enables the design of improved pre-training methods.

Empirical results show consistent performance gains across multiple benchmarks.

Abstract

Language model pre-training and derived methods are incredibly impactful in machine learning. However, there remains considerable uncertainty on exactly why pre-training helps improve performance for fine-tuning tasks. This is especially true when attempting to adapt language-model pre-training to domains outside of natural language. Here, we analyze this problem by exploring how existing pre-training methods impose relational structure in their induced per-sample latent spaces -- i.e., what constraints do pre-training methods impose on the distance or geometry between the pre-trained embeddings of two samples $\vec x_i$ and $\vec x_j$. Through a comprehensive review of existing pre-training methods, we find that this question remains open. This is true despite theoretical analyses demonstrating the importance of understanding this form of induced structure. Based on this review, we introduce a descriptive framework for pre-training that allows for a granular, comprehensive understanding of how relational structure can be induced. We present a theoretical analysis of this framework from first principles and establish a connection between the relational inductive bias of pre-training and fine-tuning performance. We also show how to use the framework to define new pre-training methods. We build upon these findings with empirical studies on benchmarks spanning 3 data modalities and ten fine-tuning tasks. These experiments validate our theoretical analyses, inform the design of novel pre-training methods, and establish consistent improvements over a compelling suite of baseline methods.