Robust Linear Initialization Enhances Adversarial Transfer Learning

Core Concepts

Robust initialization of the linear head is critical for achieving high adversarial robustness in downstream tasks, even with parameter-efficient finetuning methods.

Abstract

The paper investigates the role of initialization in adversarial transfer learning. Key insights:

A robust pretrained model is necessary for parameter-efficient finetuning (PEFT) methods to achieve satisfactory adversarial robustness on downstream tasks. PEFT methods fail or exhibit significantly degraded performance when initialized with a standard pretrained model.

Given a robust pretrained model, adversarial linear probing excels in preserving robustness from pretraining, outperforming other finetuning methods on certain datasets.

The authors propose Robust Linear Initialization (RoLI), which initializes the linear head with weights obtained through adversarial linear probing. RoLI, combined with adversarial finetuning, maximizes the inherited robustness from pretraining and achieves new state-of-the-art results across five image classification datasets.

The paper also analyzes the trade-off between robustness and training speed, showing that RoLI achieves the best performance but at the cost of increased training time.

Stats

Robust pretraining achieves 52.73% PGD robustness on CIFAR10, compared to 37.30% with standard pretraining.
RoLI - Full-FT achieves 55.42% PGD robustness on Caltech256, a 6.29% improvement over Random Linear Initialization.
RoLI - Full-FT achieves 45.57% PGD robustness on Stanford Dogs, a 20.78% improvement over Random Linear Initialization.

Quotes

"Surprisingly, all PEFT methods fail or exhibit significantly inferior performance when initialized with a standard pretrained model compared to being initialized with a robust pretrained model."
"We further demonstrate that this is mainly because linear probing excels in inheriting robustness from pretraining."

Key Insights Distilled From

Initialization Matters for Adversarial Transfer Learning

by Andong Hua,J... at arxiv.org 04-02-2024

https://arxiv.org/pdf/2312.05716.pdf

Deeper Inquiries

How can the insights from this work be applied to other domains beyond image classification, such as natural language processing or speech recognition

The insights from this work on adversarial transfer learning and the importance of initialization can be applied to other domains beyond image classification, such as natural language processing (NLP) or speech recognition. In NLP, for example, pretraining models like BERT or GPT have become standard practice. By incorporating the concept of robust pretrained models and robust linear initialization, NLP models can benefit from enhanced adversarial robustness. Adapting the RoLI approach to NLP tasks would involve initializing the linear heads of pretrained language models with weights obtained through adversarial probing, similar to how it was done in image classification tasks. This would help improve the model's robustness against adversarial attacks in NLP applications. Similarly, in speech recognition, initializing the linear heads of pretrained models with robust weights could enhance the model's ability to withstand adversarial attacks and improve overall performance in challenging scenarios.

What are the potential limitations of the proposed Robust Linear Initialization approach, and how could it be further improved or extended

The proposed Robust Linear Initialization (RoLI) approach, while effective in enhancing adversarial robustness in downstream tasks, may have some potential limitations. One limitation could be the computational cost associated with the two-step adversarial training process involved in RoLI. This could lead to longer training times, especially when compared to standard linear initialization methods. To address this limitation, researchers could explore ways to optimize the RoLI approach to reduce training time without compromising robustness. Additionally, RoLI may not be suitable for all types of models or datasets, as the effectiveness of the approach could vary depending on the complexity of the task and the nature of the data. To further improve and extend RoLI, researchers could investigate different initialization strategies, explore the use of transfer learning techniques, or incorporate additional regularization methods to enhance the model's robustness while maintaining efficiency.

Given the trade-off between robustness and training speed, are there any techniques or architectural modifications that could help bridge this gap and achieve both high robustness and efficient training

To bridge the trade-off between robustness and training speed, there are several techniques and architectural modifications that could be considered:

Regularization Techniques: Incorporating regularization techniques such as dropout, weight decay, or adversarial training during the finetuning process can help improve robustness without significantly increasing training time.

Architectural Modifications: Exploring model architectures that are inherently more robust to adversarial attacks could help achieve higher robustness without compromising training speed. Architectures with built-in mechanisms for adversarial defense, such as feature denoising layers or robust optimization layers, could be beneficial.

Ensemble Methods: Leveraging ensemble methods by combining multiple models trained with different initializations or training strategies can enhance robustness while distributing the computational load across multiple models, potentially reducing training time.

Transfer Learning: Utilizing transfer learning techniques to leverage knowledge from pretrained models in a more efficient way could help improve robustness without significantly increasing training time. Fine-tuning only specific parts of the model that are crucial for robustness could be a viable strategy.

By exploring these techniques and architectural modifications, researchers can work towards achieving both high robustness and efficient training in adversarial transfer learning tasks.