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Huiwen Dong

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2 papers

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AAAI Conference 2025 Conference Paper

On Finding Hubs in High Dimensions with Sampling

Huiwen Dong
Linghan Zeng
Zhiwen Zhao
Francesco Silvestri
Ninh Pham

Hubs are a few points that frequently appear in the k-nearest neighbors (kNN) of many other points in a high-dimensional data set. The hubs' effects, called the hubness phenomenon, degrade the performance of kNN based models in high dimensions. We present SamHub, a simple sampling approach to efficiently identify hubs with theoretical guarantees. Apart from previous works based on approximate kNN indexes, SamHub is generic and applicable to any distance measure with negligible additional memory footprint. Empirically, by sampling only 10% of points, SamHub runs significantly faster and offers higher accuracy than existing hub detection methods on many real-world data sets with dot product, L1, L2, and dynamic time warping distances. Our ablation studies of SamHub on improving kNN-based classification show potential for other high-dimensional data analysis tasks.

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AAAI Conference 2023 Conference Paper

ImageNet Pre-training Also Transfers Non-robustness

Jiaming Zhang
Jitao Sang
Qi Yi
Yunfan Yang
Huiwen Dong
Jian Yu

ImageNet pre-training has enabled state-of-the-art results on many tasks. In spite of its recognized contribution to generalization, we observed in this study that ImageNet pre-training also transfers adversarial non-robustness from pre-trained model into fine-tuned model in the downstream classification tasks. We first conducted experiments on various datasets and network backbones to uncover the adversarial non-robustness in fine-tuned model. Further analysis was conducted on examining the learned knowledge of fine-tuned model and standard model, and revealed that the reason leading to the non-robustness is the non-robust features transferred from ImageNet pre-trained model. Finally, we analyzed the preference for feature learning of the pre-trained model, explored the factors influencing robustness, and introduced a simple robust ImageNet pre-training solution. Our code is available at https://github.com/jiamingzhang94/ImageNet-Pretraining-transfers-non-robustness.

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