Publications
(*) denotes equal contribution
2024
- Make the Most of Your Data: Changing the Training Data Distribution to Improve In-distribution Generalization PerformanceDang Nguyen, Paymon Haddad, Eric Gan, and 1 more authorarXiv preprint arXiv:2404.17768, 2024
Can we modify the training data distribution to encourage the underlying optimization method toward finding solutions with superior generalization performance on in-distribution data? In this work, we approach this question for the first time by comparing the inductive bias of gradient descent (GD) with that of sharpness-aware minimization (SAM). By studying a two-layer CNN, we prove that SAM learns easy and difficult features more uniformly, particularly in early epochs. That is, SAM is less susceptible to simplicity bias compared to GD. Based on this observation, we propose USEFUL, an algorithm that clusters examples based on the network output early in training and upsamples examples with no easy features to alleviate the pitfalls of the simplicity bias. We show empirically that modifying the training data distribution in this way effectively improves the generalization performance on the original data distribution when training with (S)GD by mimicking the training dynamics of SAM. Notably, we demonstrate that our method can be combined with SAM and existing data augmentation strategies to achieve, to the best of our knowledge, state-of-the-art performance for training ResNet18 on CIFAR10, STL10, CINIC10, Tiny-ImageNet; ResNet34 on CIFAR100; and VGG19 and DenseNet121 on CIFAR10.
@article{nguyen2024make, title = {Make the Most of Your Data: Changing the Training Data Distribution to Improve In-distribution Generalization Performance}, author = {Nguyen, Dang and Haddad, Paymon and Gan, Eric and Mirzasoleiman, Baharan}, journal = {arXiv preprint arXiv:2404.17768}, year = {2024} } - Understanding the Robustness of Multi-modal Contrastive Learning to Distribution ShiftInternational Conference on Learning Representations (ICLR), 2024Data-centric Machine Learning Research (DMLR) Workshop at ICLR 2024
Recently, multimodal contrastive learning (MMCL) approaches, such as CLIP, have achieved a remarkable success in learning representations that are robust against distribution shift and generalize to new domains. Despite the empirical success, the mechanism behind learning such generalizable representations is not understood. In this work, we rigorously analyze this problem and uncover two mechanisms behind MMCL’s robustness: \emphintra-class contrasting, which allows the model to learn features with a high variance, and \emphinter-class feature sharing, where annotated details in one class help learning other classes better. Both mechanisms prevent spurious features that are over-represented in the training data to overshadow the generalizable core features. This yields superior zero-shot classification accuracy under distribution shift. Furthermore, we theoretically demonstrate the benefits of using rich captions on robustness and explore the effect of annotating different types of details in the captions. We validate our theoretical findings through experiments, including a well-designed synthetic experiment and an experiment involving training CLIP on MS COCO and evaluating the model on variations of shifted ImageNet.
@article{xue2024robustness, title = {Understanding the Robustness of Multi-modal Contrastive Learning to Distribution Shift}, author = {Xue, Yihao and Joshi, Siddharth and Nguyen, Dang and Mirzasoleiman, Baharan}, journal = {International Conference on Learning Representations (ICLR)}, workshop = {Data-centric Machine Learning Research (DMLR) Workshop at ICLR 2024}, year = {2024}, }
2023
- Self-Attention Amortized Distributional Projection Optimization for Sliced Wasserstein Point-Cloud ReconstructionKhai Nguyen*, Dang Nguyen*, and Nhat HoInternational Conference on Machine Learning (ICML), 2023
Max sliced Wasserstein (Max-SW) distance has been widely known as a solution for less discriminative projections of sliced Wasserstein (SW) distance. In applications that have various independent pairs of probability measures, amortized projection optimization is utilized to predict the “max" projecting directions given two input measures instead of using projected gradient ascent multiple times. Despite being efficient, Max-SW and its amortized version cannot guarantee metricity property due to the sub-optimality of the projected gradient ascent and the amortization gap. Therefore, we propose to replace Max-SW with distributional sliced Wasserstein distance with von Mises-Fisher (vMF) projecting distribution (v-DSW). Since v-DSW is a metric with any non-degenerate vMF distribution, its amortized version can guarantee the metricity when performing amortization. Furthermore, current amortized models are not permutation invariant and symmetric. To address the issue, we design amortized models based on self-attention architecture. In particular, we adopt efficient self-attention architectures to make the computation linear in the number of supports. With the two improvements, we derive self-attention amortized distributional projection optimization and show its appealing performance in point-cloud reconstruction and its downstream applications
@article{nguyen23self, title = {Self-Attention Amortized Distributional Projection Optimization for Sliced {W}asserstein Point-Cloud Reconstruction}, author = {Nguyen*, Khai and Nguyen*, Dang and Ho, Nhat}, journal = {International Conference on Machine Learning (ICML)}, year = {2023}, } - On Cross-Layer Alignment for Model Fusion of Heterogeneous Neural NetworksIEEE International Conference on Acoustics, Speech, and Signal Processing (ICASSP), 2023Top 3%
Layer-wise model fusion via optimal transport, named OTFusion, applies soft neuron association for unifying different pre-trained networks to save computational resources. While enjoying its success, OTFusion requires the input networks to have the same number of layers. To address this issue, we propose a novel model fusion framework, named CLAFusion, to fuse neural networks with a different number of layers, which we refer to as heterogeneous neural networks, via cross-layer alignment. The cross-layer alignment problem, which is an unbalanced assignment problem, can be solved efficiently using dynamic programming. Based on the cross-layer alignment, our framework balances the number of layers of neural networks before applying layer-wise model fusion. Our experiments indicate that CLAFusion, with an extra finetuning process, improves the accuracy of residual networks on the CIFAR10, CIFAR100, and Tiny-ImageNet datasets. Furthermore, we explore its practical usage for model compression and knowledge distillation when applying to the teacher-student setting.
@article{nguyen2021model, title = {On Cross-Layer Alignment for Model Fusion of Heterogeneous Neural Networks}, author = {Nguyen, Dang and Nguyen, Trang and Nguyen, Khai and Phung, Dinh and Bui, Hung and Ho, Nhat}, journal = {IEEE International Conference on Acoustics, Speech, and Signal Processing (ICASSP)}, note = {Top 3%}, year = {2023}, published = {true}, }
2022
- Improving Mini-batch Optimal Transport via Partial TransportationInternational Conference on Machine Learning (ICML), 2022
Mini-batch optimal transport (m-OT) has been widely used recently to deal with the memory issue of OT in large-scale applications. Despite their practicality, m-OT suffers from misspecified mappings, namely, mappings that are optimal on the mini-batch level but are partially wrong in the comparison with the optimal transportation plan between the original measures. Motivated by the misspecified mappings issue, we propose a novel mini-batch method by using partial optimal transport (POT) between mini-batch empirical measures, which we refer to as mini-batch partial optimal transport (m-POT). Leveraging the insight from the partial transportation, we explain the source of misspecified mappings from the m-OT and motivate why limiting the amount of transported masses among mini-batches via POT can alleviate the incorrect mappings. Finally, we carry out extensive experiments on various applications such as deep domain adaptation, partial domain adaptation, deep generative model, color transfer, and gradient flow to demonstrate the favorable performance of m-POT compared to current mini-batch methods.
@article{nguyen22improving, title = {Improving Mini-batch Optimal Transport via Partial Transportation}, author = {Nguyen*, Khai and Nguyen*, Dang and Vu-Le, The-Anh and Pham, Tung and Ho, Nhat}, journal = {International Conference on Machine Learning (ICML)}, year = {2022}, } - On Transportation of Mini-batches: A Hierarchical ApproachInternational Conference on Machine Learning (ICML), 2022
Mini-batch optimal transport (m-OT) has been successfully used in practical applications that involve probability measures with a very high number of supports. The m-OT solves several smaller optimal transport problems and then returns the average of their costs and transportation plans. Despite its scalability advantage, the m-OT does not consider the relationship between mini-batches which leads to undesirable estimation. Moreover, the m-OT does not approximate a proper metric between probability measures since the identity property is not satisfied. To address these problems, we propose a novel mini-batch scheme for optimal transport, named Batch of Mini-batches Optimal Transport (BoMb-OT), that finds the optimal coupling between mini-batches and it can be seen as an approximation to a well-defined distance on the space of probability measures. Furthermore, we show that the m-OT is a limit of the entropic regularized version of the BoMb-OT when the regularized parameter goes to infinity. Finally, we carry out experiments on various applications including deep generative models, deep domain adaptation, approximate Bayesian computation, color transfer, and gradient flow to show that the BoMb-OT can be widely applied and performs well in various applications.
@article{nguyen2021transportation, title = {On Transportation of Mini-batches: A Hierarchical Approach}, author = {Nguyen, Khai and Nguyen, Dang and Nguyen, Quoc and Pham, Tung and Bui, Hung and Phung, Dinh and Le, Trung and Ho, Nhat}, journal = {International Conference on Machine Learning (ICML)}, year = {2022}, }