Characterizing possible failure modes in physics-informed neural networks
Aditi S. KrishnapriyanAmir GholamiShandian ZheRobert M. KirbyMichael W. Mahoney
Demonstrates that physics-informed neural networks fail on complex differential equations due to severe optimization bottlenecks rather than limited model capacity, proposing curriculum regularization and sequence-to-sequence training to reduce prediction error by up to two orders of magnitude.
Scientific machine learning increasingly relies on physics-informed neural networks to solve complex differential equations across engineering and scientific disciplines. These frameworks integrate known physical laws directly into the neural network training objective as soft constraints or penalty terms. However, severe and often overlooked failure modes arise when applying these models to even moderately complex physical scenarios, presenting substantial operational risks for organizations deploying them in high-stakes simulations.
The article systematically evaluates why standard physics-informed neural network formulations fail on foundational differential equations and demonstrates effective algorithmic interventions to resolve these failures. The authors investigate benchmark systems covering transport, chemical reaction, and reaction-diffusion processes using fully connected networks optimized with quasi-Newton methods across varying parameter regimes, comparing predictive accuracy against known analytical solutions.
The investigation reveals three critical findings. First, standard networks succeed only under simple conditions with small physical coefficients; once convection, reaction, or diffusion coefficients increase moderately, relative prediction errors surge to between 50% and nearly 100%. Second, network architecture capacity is not the root cause. Instead, incorporating differential equations as soft constraints creates highly rugged, non-convex optimization landscapes that trap standard training algorithms in poor local minima. Third, the authors propose and evaluate two targeted solutions: curriculum regularization—which gradually scales problem complexity during training—and sequence-to-sequence time-marching, which solves the domain across sequential time intervals rather than predicting entire space-time trajectories simultaneously. Both approaches smooth the optimization landscape and reduce prediction errors by one to two orders of magnitude.
These findings indicate that relying on out-of-the-box physics-informed neural networks without specialized training workflows introduces significant simulation error and performance failure. Organizations should immediately discontinue global space-time training for complex physical systems, adopting curriculum regularization or sequential time-stepping to ensure robust model convergence and lower error variance. While the analysis is currently limited to canonical one-dimensional benchmarks, confidence in the diagnostic findings remains high, underscoring the necessity of evaluating advanced multi-dimensional implementations before large-scale deployment.
- Paper: When and why PINNs fail to train: A neural tangent kernel perspective, Sifan Wang et al. (2020). Provides a foundational neural tangent kernel analysis of training pathologies and spectral bias in physics-informed neural networks that directly contextualizes the failure modes analyzed in the source.
- Paper: DeepXDE: A Deep Learning Library for Solving Differential Equations, Lu Lu et al. (2019). Introduces the standard deep learning framework and software implementation for physics-informed neural networks whose optimization difficulties are scrutinized by the source.
- Paper: Hidden physics models: Machine learning of nonlinear partial differential equations, Maziar Raissi et al. (2017). Establishes foundational methodology for embedding nonlinear differential equations into machine learning frameworks, providing the basis for physics-informed learning.
- Paper: DGM: A deep learning algorithm for solving partial differential equations, Justin Sirignano et al. (2017). Presents early deep learning algorithms for solving partial differential equations via mesh-free differential operator losses, establishing the continuous collocation formulation analyzed in the source.
- Paper: The Deep Ritz Method: A Deep Learning-Based Numerical Algorithm for Solving Variational Problems, Weinan E et al. (2017). Demonstrates the foundational variational formulation for solving differential equations using deep neural networks and stochastic optimization.
- Paper: Theory-Guided Data Science: A New Paradigm for Scientific Discovery from Data, Anuj Karpatne et al. (2016). Conceptualizes the theory-guided data science paradigm that motivates regularizing neural network losses with scientific domain knowledge and differential equations.
- Paper: Scientific Machine Learning Through Physics–Informed Neural Networks: Where we are and What’s Next, Salvatore Cuomo et al. (2022). Synthesizes the broader landscape of physics-informed neural network architectures, applications, and practical challenges, surveying optimization remedies like those developed in the source.
- Paper: Physics-informed neural networks (PINNs) for fluid mechanics: a review, Shengze Cai et al. (2021). Surveys the practical deployment and specialized engineering of physics-informed neural networks across fluid mechanics problems where convection and diffusion failure modes are prevalent.
- Paper: KAN: Kolmogorov-Arnold Networks, Ziming Liu et al. (2025). Introduces Kolmogorov-Arnold networks as an alternative neural representation that can alleviate the optimization and expressivity bottlenecks observed in standard physics-informed architectures.
- Paper: Neural means and kernel corrections for operator learning, Yitzchak Shmalo (2026). Extends beyond conventional physics-informed neural networks by pairing neural representations with kernel corrections for operator learning and surrogate PDE modeling.
