GRepsNet: A Simple Equivariant Network for Arbitrary Matrix Groups

22 Sept 2023 (modified: 11 Feb 2024)Submitted to ICLR 2024EveryoneRevisionsBibTeX
Primary Area: general machine learning (i.e., none of the above)
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Keywords: Group equivariant networks, geometric deep learning
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TL;DR: We provide a simple equivariant architecture for arbitrary matrix groups
Abstract: Group equivariance is a strong inductive bias useful in a wide range of domains including images, point clouds, dynamical systems, and partial differential equations (PDEs). But constructing efficient equivariant networks for general groups and domains is difficult. Recent work by Finzi et al. (2021) directly solves the equivariance constraint for arbitrary matrix groups to obtain equivariant MLPs (EMLPs). However, this method does not scale well and scaling is crucial to get the best from deep learning. This necessitates the design of group equivariant networks for general domains and groups that are simple and scalable. To this end, we introduce Group Representation Networks (GRepsNets), a simple equivariant network for arbitrary matrix groups. The key intuition for our design is that using tensor representations in the hidden layers of a neural network along with appropriate mixing of various representations can lead to expressive equivariant networks, which we confirm empirically. We find GRepsNet to be competitive to EMLP on several tasks with group symmetries such as O(5), O(1, 3), and O(3) with scalars, vectors, and second-order tensors as data types. To illustrate the simplicity and generality of our network, we also use it for image classification with MLP-mixers, predicting N-body dynamics using message passing neural networks (MPNNs), and for solving PDEs using Fourier neural operators (FNOs). Surprisingly, we find that using simple first-order representations itself can yield benefits of group equivariance without additional changes in the architecture. Finally, we illustrate how higher-order tensor representations can be used for group equivariant finetuning that outperforms the existing equivariant finetuning method Basu et al. (2023b).
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Submission Number: 4426
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