Foundation models for robust machine learning
- Machine learning systems are not robust to distribution shifts---they suffer large drops in accuracy when deployed in different environments from what they were trained on. For example when satellite remote sensing models are deployed in new countries, tumor detection models are deployed in new hospitals, or wildlife conservation models are deployed in new forests, they face large drops in accuracy. In this thesis, we show that the foundation model paradigm is a principled solution that leads to state-of-the-art robustness. The foundation model paradigm consists of three steps: pretraining a model on diverse unlabeled data (e.g., satellite images from around the world) to learn general-purpose representations, adapting these models to downstream tasks that we care about, and then deploying these models in the real world. This thesis will focus on understanding and improving each of these steps for robustness. (1) First, we show that pretraining on unlabeled data learns transferable representations that improves accuracy even on domains where we had no labels. We explain why pretraining can work in a very different way from some classical intuitions of collapsing representations (domain invariance). Our theory predicts phenomena on real datasets, and leads to improved pretraining methods. (2) Next, we will show that the standard approach of adaptation (updating all the model's parameters) can distort pretrained representations and perform poorly out-of-distribution. Our theoretical analysis leads to better methods for adaptation and state-of-the-art accuracies on ImageNet and in applications such as satellite remote sensing, wildlife conservation, and radiology. (3) Finally, when we deploy models in the real world, the data distribution evolves over time which leads to a drop in model performance. We show that self-training on a model's own predictions can improve robustness to distribution shift, and explain when and why self-training works.
|Type of resource
|electronic resource; remote; computer; online resource
|1 online resource.
|Degree committee member
|Stanford University, School of Engineering
|Stanford University, Computer Science Department
|Statement of responsibility
|Submitted to the Computer Science Department.
|Thesis Ph.D. Stanford University 2023.
- © 2023 by Ananya Kumar
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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