PyHessian: Neural Networks Through the Lens of the Hessian
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Abstract (arXiv)
We present PYHESSIAN, a new scalable framework that enables fast computation of Hessian (i.e., second-order derivative) information for deep neural networks. PYHESSIAN enables fast computations of the top Hessian eigenvalues, the Hessian trace, and the full Hessian eigenvalue/spectral density, and it supports distributed-memory execution on cloud/supercomputer systems and is available as open source. This general framework can be used to analyze neural network models, including the topology of the loss landscape (i.e., curvature information) to gain insight into the behavior of different models/optimizers. To illustrate this, we analyze the effect of residual connections and Batch Normalization layers on the trainability of neural networks. One recent claim, based on simpler first-order analysis, is that residual connections and Batch Normalization make the loss landscape smoother, thus making it easier for Stochastic Gradient Descent to converge to a good solution. Our extensive analysis shows new finer-scale insights, demonstrating that, while conventional wisdom is sometimes validated, in other cases it is simply incorrect. In particular, we find that Batch Normalization does not necessarily make the loss landscape smoother, especially for shallower networks.
Key facts. Cited by 292 papers in the map (data through 14 Oct 2026). First posted on arXiv 16 Dec 2019.
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Citing papers per year: 2021: 30; 2022: 51; 2023: 51; 2024: 57; 2025: 43; 2026: 60.
292 papers.
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- 2021Characterizing possible failure modes in physics-informed neural networkscited by 643
- 2023Fine-Tuning Language Models with Just Forward Passescited by 345
- 2022How Do Vision Transformers Work?cited by 307
- 2023SqueezeLLM: Dense-and-Sparse Quantizationcited by 294
- 2023Sophia: A Scalable Stochastic Second-order Optimizer for Language Model Pre-trainingcited by 265
- 2021Fishr: Invariant Gradient Variances for Out-of-Distribution Generalizationcited by 186
- 2023Stabilizing Transformer Training by Preventing Attention Entropy Collapsecited by 161
- 2022Diverse Weight Averaging for Out-of-Distribution Generalizationcited by 148
- 2021Deep Learning Through the Lens of Example Difficultycited by 141
- 2024Adam-mini: Use Fewer Learning Rates To Gain Morecited by 137
- 2024Why Transformers Need Adam: A Hessian Perspectivecited by 124
- 2023Structured Pruning for Deep Convolutional Neural Networks: A surveycited by 122
38 more
- 2022The Right to be Forgotten in Federated Learning: An Efficient Realization with Rapid Retrainingcited by 118
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- 2022A Closer Look at Smoothness in Domain Adversarial Trainingcited by 85
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- 2022Where to Begin? On the Impact of Pre-Training and Initialization in Federated Learningcited by 71
- 2023Federated Learning of Large Language Models with Parameter-Efficient Prompt Tuning and Adaptive Optimizationcited by 65
- 2023PINNsFormer: A Transformer-Based Framework For Physics-Informed Neural Networkscited by 64
- 2023Revisiting Weighted Aggregation in Federated Learning with Neural Networkscited by 58
- 2023Gradient Norm Aware Minimization Seeks First-Order Flatness and Improves Generalizationcited by 57
- 2022Understanding Edge-of-Stability Training Dynamics with a Minimalist Examplecited by 56
- 2022Advancing Model Pruning via Bi-level Optimizationcited by 56
- 2023A Theory on Adam Instability in Large-Scale Machine Learningcited by 56
- 2022Neuromorphic Data Augmentation for Training Spiking Neural Networkscited by 52
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- 2023Improving the Model Consistency of Decentralized Federated Learningcited by 45
- 2022Anticorrelated Noise Injection for Improved Generalizationcited by 42
- 2024AdapMoE: Adaptive Sensitivity-based Expert Gating and Management for Efficient MoE Inferencecited by 42
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- 2021Taxonomizing local versus global structure in neural network loss landscapescited by 34
- 2022Robust Fine-Tuning of Deep Neural Networks with Hessian-based Generalization Guaranteescited by 34
- 2021Hessian Eigenspectra of More Realistic Nonlinear Modelscited by 33
- 2021Applications and Techniques for Fast Machine Learning in Sciencecited by 32
- 2021On the Generalization of Models Trained with SGD: Information-Theoretic Bounds and Implicationscited by 31
- 2023ImbSAM: A Closer Look at Sharpness-Aware Minimization in Class-Imbalanced Recognitioncited by 31
- 2022Escaping Saddle Points for Effective Generalization on Class-Imbalanced Datacited by 28
- 2024AZ-NAS: Assembling Zero-Cost Proxies for Network Architecture Searchcited by 28
- 2023Normalization Layers Are All That Sharpness-Aware Minimization Needscited by 27
- 2023Memorization Through the Lens of Curvature of Loss Function Around Samplescited by 27
50 most cited of 292 All 292 (JSON)
- 2026Why Heavy-Tailed Weight Spectra Predict Model Quality9 Oct 2026
- 2026A Generalisation Signal Need Not Be a Model-Selection Signal30 Sep 2026
- 2026Sparsity-Adaptive Sharpness-Aware Minimization13 Sep 2026
- 2026GPU-Enabled Large-Scale Optimization Using Randomized Linear Algebra8 Sep 2026
- 2026Post-Training Science for Supervised Fine-Tuning1 Sep 2026
- 2026Curvature-Conditioned Multiscale Momentum with Sphere Constraints for LLM Pretraining28 Aug 2026
- 2026AIM: Anchor Identity Features, Then Match for Multimodal Large Language Model Unlearning28 Aug 2026
- 2026Across the Loss Landscape with Progressive Growth25 Aug 2026
- 2026Layers Matter: Why Continual Learning Regularization Should Be Layer-Adaptive16 Aug 2026
- 2026QUASAR: Lowering the Loss Floor of Quantization-Aware Training with Loss-Aware Reconstruction14 Aug 2026
- 2026On the Implicit Flatness Bias of Sharpness-Aware Minimization: A Linear Stability Analysis with Quantitative Hyperparameter Bounds4 Aug 2026
- 2026A Defense of the Quadratic Model23 Jul 2026
38 more
- 2026A Geometric Perspective on Stabilizing Value Conflict Resolution20 Jul 2026
- 2026Gradient-Energy Guided Block-Wise Perturbations for Sharpness-Aware Minimization17 Jul 2026
- 2026Directional Curvature from Armijo Backtracking: A Low-Cost Sharpness Probe and a Calibration-Free Learning-Rate Safeguard for Adam4 Jul 2026
- 2026Curvature-Weighted Gradient Diversity: A Noise Measure for Geometry-Adaptive SGD Schedules29 Jun 2026
- 2026Exploiting Local Flatness for Efficient Out-of-Distribution Detection29 Jun 2026
- 2026Closed-Form Steepest Descent Direction toward Flat Minima: Reducing Upper Bounds on the Loss Hessian Eigenspectrum in Neural Networks27 Jun 2026
- 2026Mechanism-Driven Monitors for Preemptive Detection of LLM Training Instability26 Jun 2026
- 2026Dynamic estimation of slowly varying sequences22 Jun 2026
- 2026Dead-Direction Signatures: A Cheap Spectral Reading of Singular Complexity19 Jun 2026
- 2026Algebraic Dead Directions in LayerNorm Transformers: A Forward-Pass-Only Diagnostic at LLM Scale17 Jun 2026
- 2026Taming Curvature: Architecture Warm-Up for Stable Transformer Training15 Jun 2026
- 2026FOAM: Frequency and Operator Error-Based Adaptive Damping Method for Reducing Staleness-Oriented Error for Shampoo1 Jun 2026
- 2026Beyond ℓ2-norm and ℓ_∞-norm: A Curvature-Inspired ℓp-Norm Scheme for Deep Neural Networks1 Jun 2026
- 2026Unveiling Multi-regime Patterns in SciML: Distinct Failure Modes and Regime-specific Optimization27 May 2026
- 2026Stochastic Estimation of the Layer-wise Hessian Trace for Monitoring Neural-network Training25 May 2026
- 2026Momentum Streams for Optimizer-Inspired Transformers23 May 2026
- 2026Batch Normalization Amplifies Memorization and Privacy Risks23 May 2026
- 2026AMUSE: Anytime Muon with Stable Gradient Evaluation21 May 2026
- 2026WinQ: Accelerating Quantization-Aware Training of Language Models Around Saddle Points17 May 2026
- 2026Fix the Loss, Not the Radius: Rethinking the Adversarial Perturbation of Sharpness-Aware Minimization11 May 2026
- 2026Hessian Surgery: Class-Targeted Post-Hoc Rebalancing via Hessian Spike Perturbation8 May 2026
- 2026Adaptive Selection of LoRA Components in Privacy-Preserving Federated Learning7 May 2026
- 2026Learning Dynamics of Zeroth-Order Optimization: A Kernel Perspective5 May 2026
- 2026When Does Removing LayerNorm Help? Activation Bounding as a Regime-Dependent Implicit Regularizer25 Apr 2026
- 2026Curvature-Aligned Probing for Local Loss-Landscape Stabilization16 Apr 2026
- 2026Wolkowicz-Styan Upper Bound on the Hessian Eigenspectrum for Cross-Entropy Loss in Nonlinear Smooth Neural Networks11 Apr 2026
- 2026Stochastic Dimension Implicit Functional Projections for Global Integral Conservation in High-Dimensional PINNs31 Mar 2026
- 2026Second-Order, First-Class: A Composable Stack for Curvature-Aware Training26 Mar 2026
- 2026Combining Adam and its Inverse Counterpart to Enhance Generalization of Deep Learning Optimizers7 Mar 2026
- 2026Dynamic Momentum Recalibration in Online Gradient Learning6 Mar 2026
- 2026Does Sparse Connectivity Improve Generalization? Convolutional Networks Below the Edge of Stability5 Mar 2026
- 2026Accelerating LLM Pre-Training through Flat-Direction Dynamics Enhancement26 Feb 2026
- 2026Towards Robust Scaling Laws for Optimizers7 Feb 2026
- 2026Convex Dominance in Deep Learning I: A Scaling Law of Loss and Learning Rate6 Feb 2026
- 2026Landscaper: Understanding Loss Landscapes Through Multi-Dimensional Topological Analysis6 Feb 2026
- 2026Decoupling Variance and Scale-Invariant Updates in Adaptive Gradient Descent for Unified Vector and Matrix Optimization6 Feb 2026
- 2026Visualizing the loss landscapes of physics-informed neural networks5 Feb 2026
- 2026On the Superlinear Relationship between SGD Noise Covariance and Loss Landscape Curvature5 Feb 2026
50 newest of 292 All 292 (JSON)
- 2021Characterizing possible failure modes in physics-informed neural networkscited by 643
- 2023Fine-Tuning Language Models with Just Forward Passescited by 345
- 2022How Do Vision Transformers Work?cited by 307
- 2023SqueezeLLM: Dense-and-Sparse Quantizationcited by 294
- 2023Sophia: A Scalable Stochastic Second-order Optimizer for Language Model Pre-trainingcited by 265
- 2021Fishr: Invariant Gradient Variances for Out-of-Distribution Generalizationcited by 186
- 2023Stabilizing Transformer Training by Preventing Attention Entropy Collapsecited by 161
- 2022Diverse Weight Averaging for Out-of-Distribution Generalizationcited by 148
- 2021Deep Learning Through the Lens of Example Difficultycited by 141
- 2024Adam-mini: Use Fewer Learning Rates To Gain Morecited by 137
- 2024Why Transformers Need Adam: A Hessian Perspectivecited by 124
- 2023Structured Pruning for Deep Convolutional Neural Networks: A surveycited by 122
12 most cited of 282 All 282 (JSON)
- 2026Why Heavy-Tailed Weight Spectra Predict Model Quality9 Oct 2026
- 2026A Generalisation Signal Need Not Be a Model-Selection Signal30 Sep 2026
- 2026Sparsity-Adaptive Sharpness-Aware Minimization13 Sep 2026
- 2026GPU-Enabled Large-Scale Optimization Using Randomized Linear Algebra8 Sep 2026
- 2026Curvature-Conditioned Multiscale Momentum with Sphere Constraints for LLM Pretraining28 Aug 2026
- 2026Across the Loss Landscape with Progressive Growth25 Aug 2026
- 2026Layers Matter: Why Continual Learning Regularization Should Be Layer-Adaptive16 Aug 2026
- 2026QUASAR: Lowering the Loss Floor of Quantization-Aware Training with Loss-Aware Reconstruction14 Aug 2026
- 2026On the Implicit Flatness Bias of Sharpness-Aware Minimization: A Linear Stability Analysis with Quantitative Hyperparameter Bounds4 Aug 2026
- 2026A Defense of the Quadratic Model23 Jul 2026
- 2026Gradient-Energy Guided Block-Wise Perturbations for Sharpness-Aware Minimization17 Jul 2026
- 2026Directional Curvature from Armijo Backtracking: A Low-Cost Sharpness Probe and a Calibration-Free Learning-Rate Safeguard for Adam4 Jul 2026
12 newest of 282 All 282 (JSON)