Fully connected Graph Transformers (GT) have rapidly become prominent in
the static graph community as an alternative to Message-Passing models, which
suffer from a lack of expressivity, oversquashing, and under-reaching. However,
in a dynamic context, by interconnecting all nodes at multiple snapshots with
self-attention,GT loose both structural and temporal information. In this work, we
introduce Supra-LAplacian encoding for spatio-temporal TransformErs (SLATE),
a new spatio-temporal encoding to leverage the GT architecture while keeping
spatio-temporal information. Specifically, we transform Discrete Time Dynamic
Graphs into multi-layer graphs and take advantage of the spectral properties of their
associated supra-Laplacian matrix. Our second contribution explicitly model nodes’
pairwise relationships with a cross-attention mechanism, providing an accurate edge
representation for dynamic link prediction. SLATE outperforms numerous state-ofthe-art methods based on Message-Passing Graph Neural Networks combined with
recurrent models (e.g. , LSTM), and Dynamic Graph Transformers, on 9 datasets.
Code and instructions to reproduce our results will be open-sourced.
@article{Karmim2024,author={Karmim, Yannis and Lafon, Marc and Fournier S’niehotta, Raphaël and Thome, Nicolas},journal={Conference on Neural Information Processing Systems (NeurIPS 2024)},title={{Supra-Laplacian Encoding for Transformer on Dynamic Graphs}},year={2024},}
ECCV
GalLoP: Learning Global and Local Prompts for Vision-Language Models
Marc Lafon, Elias Ramzi, Clément Rambour, and
2 more authors
Proceedings of the 18th European Conference on Computer Vision, Milan, Italy, 2024, 2024
Prompt learning has been widely adopted to efficiently adapt vision-language models (VLMs), e.g. CLIP, for few-shot image classification. Despite their success, most prompt learning methods trade-off between classification accuracy and robustness, e.g. in domain generalization or outof-distribution (OOD) detection. In this work, we introduce Global-Local Prompts (GalLoP), a new prompt learning method that learns multiple diverse prompts leveraging both global and local visual features. The training of the local prompts relies on local features with an enhanced vision-text alignment. To focus only on pertinent features, this local alignment is coupled with a sparsity strategy in the selection of the local features. We enforce diversity on the set of prompts using a new “prompt dropout” technique and a multiscale strategy on the local prompts. GalLoP outperforms previous prompt learning methods on accuracy on eleven datasets in different few shots settings and with various backbones. Furthermore, GalLoP shows strong robustness performances in both domain generalization and OOD detection, even outperforming dedicated OOD detection methods. Code and instructions to reproduce our results will be open-sourced.
@article{LafonRamzi2024,author={Lafon, Marc and Ramzi, Elias and Rambour, Clément and Audebert, Nicolas and Thome, Nicolas},journal={Proceedings of the 18th European Conference on Computer Vision, Milan, Italy, 2024},title={{GalLoP: Learning Global and Local Prompts for Vision-Language Models}},year={2024},}
2023
ICML
Hybrid Energy Based Model in the Feature Space for Out-of-Distribution Detection
Marc Lafon, Elias Ramzi, Clément Rambour, and
1 more author
Proceedings of the 40 th International Conference on Machine
Learning, Honolulu, Hawaii, USA. PMLR 202, 2023, 2023
Out-of-distribution (OOD) detection is a critical requirement for the deployment of deep neural networks. This paper introduces the HEAT model, a new post-hoc OOD detection method estimating the density of in-distribution (ID) samples using hybrid energy-based models (EBM) in the feature space of a pre-trained backbone. HEAT complements prior density estimators of the ID density, e.g. parametric models like the Gaussian Mixture Model (GMM), to provide an accurate yet robust density estimation. A second contribution is to leverage the EBM framework to provide a unified density estimation and to compose several energy terms. Extensive experiments demonstrate the significance of the two contributions. HEAT sets new state-of-the-art OOD detection results on the CIFAR-10 / CIFAR100 benchmark as well as on the large-scale Imagenet benchmark. The code is available at: github.com/MarcLafon/heatood.
@article{Lafon2023,author={Lafon, Marc and Ramzi, Elias and Rambour, Clément and Thome, Nicolas},journal={Proceedings of the 40 th International Conference on Machine
Learning, Honolulu, Hawaii, USA. PMLR 202, 2023},title={{Hybrid Energy Based Model in the Feature Space for Out-of-Distribution Detection}},year={2023},}
2022
NeurIPS
Energy Correction Model in the Feature Space for Out-of-Distribution Detection
In this work, we study the out-of-distribution (OOD) detection problem through the use of the feature space of a pre-trained deep classifier. We show that learning the density of in-distribution (ID) features with an energy-based models (EBM) leads to competitive detection results. However, we found that the non-mixing of MCMC sampling during the EBM’s training undermines its detection performance. To overcome this an energy-based correction of a mixture of class-conditional Gaussian distributions. We obtains favorable results when compared to a strong baseline like the KNN detector on the CIFAR-10/CIFAR-100 OOD detection benchmarks.
@article{Lafon2022,author={Lafon, Marc and Clément, Rambour and Thome, Nicolas},journal={NeurIPS Workshop on Machine Learning Safety},title={{Energy Correction Model in the Feature Space for Out-of-Distribution Detection}},year={2022},}
2021
ICML
Beyond First-Order Uncertainty Estimation with Evidential Models for Open-World Recognition
Charles Corbière, Marc Lafon, Nicolas Thome, and
2 more authors
ICML Workshop on Uncertainty and Robustness in Deep Learning, 2021
In this paper, we tackle the challenge of jointly quantifying in-distribution and out-of-distribution (OOD) uncertainties. We introduce KLoS, a KL-divergence measure defined on the class-probability simplex. By leveraging the second-order uncertainty representation provided by evi-dential models, KLoS captures more than existing first-order uncertainty measures such as predic-tive entropy. We design an auxiliary neural network , KLoSNet, to learn a refined measure directly aligned with the evidential training objective. Experiments show that KLoSNet acts as a class-wise density estimator and outperforms current uncertainty measures in the realistic context where no OOD data is available during training. We also report comparisons in the presence of OOD training samples, which shed a new light on the impact of the vicinity of this data with OOD test data.
@article{Corbiere2021,author={Corbière, Charles and Lafon, Marc and Thome, Nicolas and Cord, Matthieu and Pérez, Patrick},journal={ICML Workshop on Uncertainty and Robustness in Deep Learning},title={{Beyond First-Order Uncertainty Estimation with Evidential Models for Open-World Recognition}},year={2021},}
arxiv
Understanding the Double Descent Phenomenon in Deep Learning
Combining empirical risk minimization with capacity control is a classical strategy in machine learning when trying to control the generalization gap and avoid overfitting, as the model class capacity gets larger. Yet, in modern deep learning practice, very large over-parameterized models (e.g. neural networks) are optimized to fit perfectly the training data and still obtain great generalization performance. Past the interpolation point, increasing model complexity seems to actually lower the test error. In this tutorial, we explain the concept of double descent introduced by Belkin et al 2019, and its mechanisms. Section 1 sets the classical statistical learning framework and introduces the double descent phenomenon. By looking at a number of examples, section 2 introduces inductive biases that appear to have a key role in double descent by selecting, among the multiple interpolating solutions, a smooth empirical risk minimizer. Finally, section 3 explores the double descent with two linear models, and gives other points of view from recent related works.
@article{Lafon2021,author={Lafon, Marc and Thomas, Alexandre},journal={},title={{Understanding the Double Descent Phenomenon in Deep Learning}},year={2021},}