Limitations of the Empirical Fisher Approximation for Natural Gradient Descent
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Abstract (arXiv)
Natural gradient descent, which preconditions a gradient descent update with the Fisher information matrix of the underlying statistical model, is a way to capture partial second-order information. Several highly visible works have advocated an approximation known as the empirical Fisher, drawing connections between approximate second-order methods and heuristics like Adam. We dispute this argument by showing that the empirical Fisher---unlike the Fisher---does not generally capture second-order information. We further argue that the conditions under which the empirical Fisher approaches the Fisher (and the Hessian) are unlikely to be met in practice, and that, even on simple optimization problems, the pathologies of the empirical Fisher can have undesirable effects.
Key facts. Cited by 213 papers in the map (data through 7 Oct 2026). First posted on arXiv 29 May 2019.
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Citing papers per year: 2021: 31; 2022: 17; 2023: 35; 2024: 32; 2025: 37; 2026: 61.
213 papers.
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50 most cited of 213 All 213 (JSON)
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- 2026POP: Prefill-Only Pruning for Efficient Large Model Inference3 Feb 2026
- 2024Multimodal LLM Guided Exploration and Active Mapping using Fisher Information22 Oct 2024
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- 2021Laplace Redux -- Effortless Bayesian Deep Learningcited by 359
- 2023Sophia: A Scalable Stochastic Second-order Optimizer for Language Model Pre-trainingcited by 260
- 2021Training Neural Networks with Fixed Sparse Maskscited by 212
- 2021Fishr: Invariant Gradient Variances for Out-of-Distribution Generalizationcited by 186
- 2023Bayesian Low-rank Adaptation for Large Language Modelscited by 112
- 2021Scalable Marginal Likelihood Estimation for Model Selection in Deep Learningcited by 105
- 2024Heavy-Tailed Class Imbalance and Why Adam Outperforms Gradient Descent on Language Modelscited by 78
- 2023A Distributed Data-Parallel PyTorch Implementation of the Distributed Shampoo Optimizer for Training Neural Networks At-Scalecited by 69
- 2021Spectral Normalisation for Deep Reinforcement Learning: an Optimisation Perspectivecited by 64
- 2021M-FAC: Efficient Matrix-Free Approximations of Second-Order Informationcited by 54
- 2024A New Perspective on Shampoo's Preconditionercited by 54
- 2022A Simple Approach to Improve Single-Model Deep Uncertainty via Distance-Awarenesscited by 49
12 most cited of 198 All 198 (JSON)
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- 2026CoeF-SFL: Preserving Collaborative Server-Client Learning with Enhanced Communication Efficiency28 Sep 2026
- 2026The cost of useful natural gradient updates27 Sep 2026
- 2026Understanding the Subspace Stabilization of the Hessian and Gradient Covariance Matrix25 Sep 2026
- 2026Optimal Pruning for Neural Architectures using Fisher Information Distances14 Sep 2026
- 2026Beyond the Matrix Sign: Quadratic Spectral Descent7 Sep 2026
- 2026FAMPWQ: Fisher Information-based Adaptive Mixed Precision Weight Quantization for Effective LLM Inference24 Aug 2026
- 2026Loss-Parameterized Fisher Width Along Learning Trajectories21 Aug 2026
- 2026Layers Matter: Why Continual Learning Regularization Should Be Layer-Adaptive16 Aug 2026
- 2026When Do Concepts Become Functionally Sufficient During Language-Model Training?15 Aug 2026
- 2026Fisher8: Stabilizing Neural Heteroscedastic Regression via Output-Layer Fisher Geometry11 Aug 2026
- 2026Second-Order Muon Done Right: A Principled Marriage of Spectral Geometry and Curvature10 Aug 2026
12 newest of 198 All 198 (JSON)