Meta-Learning Symmetries by Reparameterization

Authors: Allan Zhou, Tom Knowles, Chelsea Finn

Submitted to arXiv on 06 Jul. 2020
Abstract

Many successful deep learning architectures are equivariant to certain transformations in order to conserve parameters and improve generalization: most famously, convolution layers are equivariant to shifts of the input. This approach only works when practitioners know a-priori symmetries of the task and can manually construct an architecture with the corresponding equivariances. Our goal is a general approach for learning equivariances from data, without needing prior knowledge of a task's symmetries or custom task-specific architectures. We present a method for learning and encoding equivariances into networks by learning corresponding parameter sharing patterns from data. Our method can provably encode equivariance-inducing parameter sharing for any finite group of symmetry transformations, and we find experimentally that it can automatically learn a variety of equivariances from symmetries in data. We provide our experiment code and pre-trained models at https://github.com/AllanYangZhou/metalearning-symmetries.

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    Learning Probabilistic Symmetrization for Architecture Agnostic Equivariance
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    Learning Probabilistic Symmetrization makes an arbitrary base model equivariant by learning a probabilistic symmetrization, rather than learning parameter-sharing patterns from data.

    Abstract

    We present a novel framework to overcome the limitations of equivariant architectures in learning functions with group symmetries. In contrary to equivariant architectures, we use an arbitrary base model (such as an MLP or a transformer) and symmetrize it to be equivariant to the given group by employing a small equivariant network that parameterizes the probabilistic distribution underlying the symmetrization. The distribution is end-to-end trained with the base model which can maximize performance while reducing sample complexity of symmetrization. We show that this approach ensures not only equivariance to given group but also universal approximation capability in expectation. We implemen…

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    Equivariance Discovery by Learned Parameter-Sharing formulates symmetry discovery as optimization over parameter-sharing schemes and cites this paper.

    Abstract

    Designing equivariance as an inductive bias into deep-nets has been a prominent approach to build effective models, e.g., a convolutional neural network incorporates translation equivariance. However, incorporating these inductive biases requires knowledge about the equivariance properties of the data, which may not be available, e.g., when encountering a new domain. To address this, we study how to discover interpretable equivariances from data. Specifically, we formulate this discovery process as an optimization problem over a model's parameter-sharing schemes. We propose to use the partition distance to empirically quantify the accuracy of the recovered equivariance. Also, we theoreticall…

  3. Very close Another approach to the problem
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    Symmetry From Scratch induces equivariance by teaching general architectures symmetries as a supervised task, while this paper learns parameter-sharing patterns from data.

    Abstract

    In machine learning datasets with symmetries, the paradigm for backward compatibility with symmetry-breaking has been to relax equivariant architectural constraints, engineering extra weights to differentiate symmetries of interest. However, this process becomes increasingly over-engineered as models are geared towards specific symmetries/asymmetries hardwired of a particular set of equivariant basis functions. In this work, we introduce symmetry-cloning, a method for inducing equivariance in machine learning models. We show that general machine learning architectures (i.e., MLPs) can learn symmetries directly as a supervised learning task from group equivariant architectures and retain/brea…

  4. Very close Groundwork for this paper Cited by this paper
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    Equivariance Through Parameter-Sharing establishes how parameter symmetries and sharing schemes induce group equivariance, which this paper cites.

    Abstract

    We propose to study equivariance in deep neural networks through parameter symmetries. In particular, given a group G that acts discretely on the input and output of a standard neural network layer ϕW : ℝM → ℝN, we show that ϕW is equivariant with respect to G-action iff G explains the symmetries of the network parameters W. Inspired by this observation, we then propose two parameter-sharing schemes to induce the desirable symmetry on W. Our procedure for tying the parameters achieves G-equivariance and, under some conditions on the action of G, it guarantees sensitivity to all other permutation groups outside G.

  5. Very close Builds on this paper Cites this paper
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    Kaitlin Maile, Dennis G. Wilson, P. Forré · 2022 · International Conference on Learning Representations · cited 10 times · Not summarized yet

    Equivariance-aware Architectural Optimization adapts equivariance constraints across groups and cites this paper's work on learning symmetries.

    Abstract

    Incorporating equivariance to symmetry groups as a constraint during neural network training can improve performance and generalization for tasks exhibiting those symmetries, but such symmetries are often not perfectly nor explicitly present. This motivates algorithmically optimizing the architectural constraints imposed by equivariance. We propose the equivariance relaxation morphism, which preserves functionality while reparameterizing a group equivariant layer to operate with equivariance constraints on a subgroup, as well as the [G]-mixed equivariant layer, which mixes layers constrained to different groups to enable within-layer equivariance optimization. We further present evolutionary…

  6. Very close Builds on this paper Cites this paper
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    Learning Layer-wise Equivariances Automatically also learns symmetry constraints and weight connectivity from data using gradients, and cites this paper.

    Abstract

    Convolutions encode equivariance symmetries into neural networks leading to better generalisation performance. However, symmetries provide fixed hard constraints on the functions a network can represent, need to be specified in advance, and can not be adapted. Our goal is to allow flexible symmetry constraints that can automatically be learned from data using gradients. Learning symmetry and associated weight connectivity structures from scratch is difficult for two reasons. First, it requires efficient and flexible parameterisations of layer-wise equivariances. Secondly, symmetries act as constraints and are therefore not encouraged by training losses measuring data fit. To overcome these c…

  7. Very close Builds on this paper Cites this paper
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    E. Bekkers, Alejandro García-Castellanos, Thijs P. Kuipers et al. · 2024 · Neural Information Processing Systems · cited 6 times · Not summarized yet

    Learning Symmetries via Weight-Sharing with Doubly Stochastic Tensors discovers symmetries through weight sharing and cites this paper.

    Abstract

    Group equivariance has emerged as a valuable inductive bias in deep learning, enhancing generalization, data efficiency, and robustness. Classically, group equivariant methods require the groups of interest to be known beforehand, which may not be realistic for real-world data. Additionally, baking in fixed group equivariance may impose overly restrictive constraints on model architecture. This highlights the need for methods that can dynamically discover and apply symmetries as soft constraints. For neural network architectures, equivariance is commonly achieved through group transformations of a canonical weight tensor, resulting in weight sharing over a given group $G$. In this work, we p…

  8. Very close Broader context
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    A Tale of Two Symmetries analyzes optimization and loss landscapes in equivariant models, rather than discovering equivariances from data.

    Abstract

    Equivariant neural networks have proven to be effective for tasks with known underlying symmetries. However, optimizing equivariant networks can be tricky and best training practices are less established than for standard networks. In particular, recent works have found small training benefits from relaxing equivariance constraints. This raises the question: do equivariance constraints introduce fundamental obstacles to optimization? Or do they simply require different hyperparameter tuning? In this work, we investigate this question through a theoretical analysis of the loss landscape geometry. We focus on networks built using permutation representations, which we can view as a subset of un…

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    Abstract

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  4. Close Same method, another problem
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  5. Related Same method, another problem A method it uses
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    Nichita Diaconu, Daniel E. Worrall · 2019 · International Conference on Machine Learning · cited 88 times · Not summarized yet

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    Abstract

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Papers that cite it

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    Abstract

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  4. Close Same method, another problem
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  5. Close Broader context
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    Abstract

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