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Test-Time Adaptation of Vision Transformers with Forward-Only Prompt Learning


Centrala begrepp
A novel forward-only adaptation method that learns prompts via a derivative-free optimizer and aligns activations to the source domain, enabling efficient test-time adaptation on resource-constrained devices without backpropagation.
Sammanfattning

The paper proposes a novel test-time adaptation (TTA) method called Forward-Only Adaptation (FOA) that can efficiently adapt vision transformer (ViT) models to out-of-distribution (OOD) test samples without using any backpropagation.

Key highlights:

  • FOA introduces a new prompt as the model's input and learns this prompt via a derivative-free covariance matrix adaptation (CMA) evolution strategy, without modifying the model weights.
  • FOA devises a novel unsupervised fitness function for CMA that measures the discrepancy between the activation statistics of OOD test samples and in-distribution source samples, providing stable learning signals.
  • FOA further boosts adaptation by directly shifting the activations of OOD test samples towards the source domain, without backpropagation.
  • Experiments show FOA outperforms gradient-based TTA methods on full-precision ViT models, and significantly outperforms them on quantized 8-bit ViT models, with up to 24-fold memory reduction.
  • FOA's forward-only nature makes it compatible with resource-constrained devices like smartphones and FPGAs that lack backpropagation support, greatly expanding the real-world applicability of TTA.
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Statistik
The average accuracy of FOA on ImageNet-C (level 5) is 66.3%, outperforming gradient-based TENT (59.6%) on full-precision ViT. FOA on 8-bit quantized ViT achieves 63.5% accuracy, surpassing TENT on full-precision ViT, while reducing the run-time memory usage by up to 24-fold. FOA reduces the average ECE on ImageNet-C from 18.5% (TENT) to 3.2%.
Citat
"Without using any backpropagation and altering model weights, FOA runs on quantized 8-bit ViT outperforms gradient-based TENT on full-precision 32-bit ViT, while achieving an up to 24-fold memory reduction on ImageNet-C." "Notably, FOA on 8-bit quantized ViT surpasses the performance of the gradient-based TENT method using a full precision 32-bit ViT on ImageNet-C, achieving 63.5% accuracy (our FOA, 8-bit) vs. 59.6% (TENT, 32-bit)."

Viktiga insikter från

by Shuaicheng N... arxiv.org 04-03-2024

https://arxiv.org/pdf/2404.01650.pdf
Test-Time Model Adaptation with Only Forward Passes

Djupare frågor

How can the proposed forward-only adaptation approach be extended to other types of neural network architectures beyond vision transformers

The forward-only adaptation approach proposed in the study can be extended to other types of neural network architectures beyond vision transformers by following a similar framework of prompt adaptation and activation shifting. For different architectures such as CNNs, RNNs, or GANs, the key lies in identifying the input features that can be adapted at test time and designing a fitness function that guides the adaptation process effectively. For CNNs, the input features could be specific layers or channels that can be adjusted to align with the source domain. In RNNs, the hidden states or embeddings can be modified to improve adaptation to out-of-distribution samples. GANs could benefit from adapting the generator's input noise or latent space to enhance performance on unseen data. The activation shifting scheme can also be applied to different architectures by identifying the relevant activation layers that need adjustment. By dynamically shifting the activations towards the source domain, the model can better generalize to new data distributions. Overall, the principles of prompt adaptation and activation shifting can be applied to a wide range of neural network architectures, with adjustments made to suit the specific characteristics and requirements of each model type.

What are the potential limitations or failure cases of the activation shifting scheme, and how can it be further improved

The activation shifting scheme, while effective in improving adaptation performance, may have potential limitations and failure cases that need to be addressed for further improvement: Overfitting: The activation shifting scheme may lead to overfitting if the shifting is too aggressive or if the model becomes too specialized to the source domain. Regularization techniques or adaptive shifting strategies can help mitigate this risk. Limited Generalization: The activation shifting may not always capture the full complexity of distribution shifts, especially in cases of highly diverse or complex out-of-distribution samples. Incorporating more sophisticated alignment methods or data augmentation techniques can enhance generalization capabilities. Computational Overhead: The activation shifting process may introduce additional computational overhead, especially in real-time applications with strict constraints. Optimizing the shifting algorithm for efficiency and exploring parallel processing techniques can help mitigate this issue. To further improve the activation shifting scheme, researchers can explore adaptive shifting strategies that dynamically adjust the shifting based on the characteristics of the input data. Additionally, incorporating domain adaptation techniques or leveraging meta-learning approaches can enhance the model's ability to adapt to a wide range of distribution shifts.

Given the efficiency and memory advantages of FOA, how can it be leveraged to enable test-time adaptation in real-time applications with strict computational constraints, such as autonomous driving or robotics

To leverage the efficiency and memory advantages of FOA for real-time applications with strict computational constraints, such as autonomous driving or robotics, the following strategies can be implemented: Hardware Optimization: Implement FOA on specialized hardware accelerators or edge devices with optimized architectures for neural network inference. This can improve computational efficiency and reduce memory usage for real-time applications. Quantization and Compression: Utilize model quantization techniques to further reduce the memory footprint of the adapted model. Compression algorithms can be applied to minimize the storage requirements while maintaining performance. Incremental Learning: Implement incremental learning strategies with FOA to adapt the model gradually over time, reducing the computational burden of updating the model in real-time. This approach can enable continuous adaptation to changing environments without significant resource overhead. Dynamic Resource Allocation: Implement dynamic resource allocation mechanisms that allocate computational resources based on the current workload and performance requirements. This can ensure optimal utilization of resources for real-time adaptation tasks. By integrating these strategies, FOA can be effectively leveraged in real-time applications with strict computational constraints, enabling efficient and adaptive model adaptation in scenarios such as autonomous driving and robotics.
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