REVIEW 4 major objections 5 minor 43 references
A Neural Operator based on Dynamic Mode Decomposition
T0 review · 4 major / 5 minor · reviewed 2026-08-06 · deepseek-v4-flash
Pith's one-line read A neural operator that couples dynamic mode decomposition with a branch-trunk network reproduces heat, Laplace, and Burgers solutions, with error bounded by (L_G + 2L_H)ε.
desk verdict A modest hybrid idea undercut by an invalid error bound and missing empirical comparisons. read the letter →
The pith
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
The reading
What carries the argument
The central mechanism is the DMD-in-the-loop architecture of Eqs. (11)–(12). Dynamic mode decomposition — the working assumption that snapshots evolve under a linear operator $x_{k+1} = A x_k$, recovered by the singular value decomposition of the data matrix, truncation to rank $r$, and diagonalization of the projected operator $\tilde{A} = U_r^* X' V_r \Sigma_r^{-1}$ — supplies spatial modes $\Phi$ and scalar dynamics that feed dedicated 'modes' and 'dynamics' branch networks; a trunk network encodes the prediction coordinate, and the branches are combined through Hadamard products and summation in the style of a DeepONet. The second load-bearing piece is Theorem 1, whose bound $(L_G + 2L_H)\epsilon$ turns the rank-truncation error $\epsilon$ into a certificate on operator error: the proof uses the Eckart–Young theorem to replace the DMD modes of the data by those of its optimal rank-$r$ approximation, and Lipschitz continuity of both the target map $G$ and the network $H$ to control the propagation of $\epsilon$. The architecture is what connects the two: because the DMD modes and dynamics are explicit inputs rather than learned features, the truncation error of DMD is the only approximation error the bound must track.
What would settle it
Generate a test family of initial or boundary conditions whose true solutions are dominated by components orthogonal to the first ten DMD modes of the training data on the same 10×10 grid (for example, high-frequency boundary values), train with DMD rank fixed at 10, and measure test error: if the error jumps far above training-era levels, the DMD information bottleneck is refuted as the assumption that carries the method. A second, cheaper check is quantitative: measure the Lipschitz constants $L_G$ and $L_H$ and the Frobenius truncation error $\epsilon$ on the actual test snapshots, and test whether observed reconstruction errors respect the claimed $(L_G + 2L_H)\epsilon$ bound.
Extended reading notes
Core claim
On the paper's own terms, the discovery is a new class of DMD-enhanced neural operator $G_\theta^{\mathrm{DMD}}: \mathcal{A} \to \mathcal{U}$ described by Eqs. (11)–(12), in which the prediction at a point $x$ is a sum over trunk basis functions of products of branch outputs: branches for DMD spatial modes $\varphi_k$, branches for DMD dynamics $\psi_k$, branches for the differential-operator values, and a trunk for the grid coordinates, combined by Hadamard products. The DMD decomposition is computed once from the training function values (Algorithm 2, step 6) with rank 10, so the network only learns how to combine physically meaningful modes and dynamics with the geometry rather than discovering latent structure from scratch. The theoretical guarantee is Theorem 1: if the solution map $G$ is $L_G$-Lipschitz and the network $H$ is $L_H$-Lipschitz, the error of the DMD operator against $G$ is at most $(L_G + 2L_H)\epsilon$, where $\epsilon$ is the Frobenius-norm error of the optimal rank-$r$ SVD approximation, and the proof invokes the Eckart–Young theorem to show that the DMD modes of the truncated data coincide with those of the full data. Experiments on the Laplace, heat, and Burgers equations — 10×10 grids, 1000 samples, DMD rank 10 — report training and test losses that fall by one to two orders of magnitude over 90 epochs, with the largest residual errors near boundaries and corners, and the abstract claims high reconstruction accuracy in comparative analysis with DeepONet and FNO.
Load-bearing premise
The load-bearing premise is that the rank-truncated DMD modes and dynamics computed once from the training snapshots retain all the solution structure the network needs, so anything the rank-10 truncation discards is also information the surrogate cannot recover for new boundary or initial conditions.
Editorial extensions
If this is right
- Reconstruction accuracy becomes predictable before training: under the theorem, test error is controlled by the DMD rank-truncation error and the two Lipschitz constants, so a user who measures these on a small holdout set can certify accuracy in advance.
- The same wiring ports across equations: because the mode and dynamics branches are equation-agnostic inputs, one architecture should handle any problem family whose snapshots admit a low-rank DMD representation, which is what the three experiments demonstrate.
- Data needs shrink relative to purely data-driven operators: the DMD pass fixes the dominant degrees of freedom once, so the network only learns a combination rule rather than discovering latent structure from scratch.
- Small networks are not only cheaper but also accuracy-optimal under the bound, since an over-parameterized network with a large Lipschitz constant increases the (L_G + 2L_H) prefactor and worsens the worst-case error.
- Inference stays fast: DMD modes are computed once at train time and a new solution is a single forward pass, matching the speed advantage claimed for neural operators over repeated classical solving.
Reading between the lines
- A direct test the paper leaves implicit: hold the network architecture fixed and vary only the DMD rank; if test error tracks the truncation error epsilon as the theorem predicts, the bound is doing real work, and if not, one of the proof's assumptions is the weak point.
- The largest reported errors sit near boundaries and corners in all three experiments, which points to a testable variant the paper does not explore: keep the DMD operator in the interior and let a classical boundary-layer solver own the edges, then compare total error.
- An adaptive-rank extension is the natural next step: replace the fixed rank-10 DMD by a singular-value energy criterion so branch input width varies with the data, which the modular architecture can absorb by construction.
- The method is most likely to pay off on parametric families where linear dynamics already describe the physics decently — thermal transients, mild-convection flows — and least on shock-dominated problems, where rank-10 linear reconstruction cannot represent the sharp moving fronts the experiments already show as boundary errors.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper proposes a hybrid neural operator that combines Dynamic Mode Decomposition (DMD) with a branch-trunk deep network for approximating PDE solution operators. The model extracts DMD modes and dynamics from training snapshots and feeds them to specialized branches, with a trunk net over spatial coordinates. The main formal claim is Theorem 1, an error bound of (L_G+2L_H)epsilon for the DMD-neural operator. Empirical sections report training and test losses for the Laplace, heat, and Burgers equations, and the abstract asserts high reconstruction accuracy relative to DeepONet and FNO. The paper also includes data-generation algorithms, architecture diagrams, a code repository link, and a software patent reference.
Significance. If the theorem and comparisons were valid, the paper would make a modest contribution: a lightweight hybrid operator with interpretable DMD modes and a rigorous error bound. The architectural idea is reasonable, and the availability of source code and data-generation algorithms is a positive feature. However, the theoretical result as stated does not follow from the assumptions, and the empirical comparison promised in the abstract is not reported. As it stands, the paper does not establish either of its two central claims, so its current significance is limited.
major comments (4)
- [Section 2.4.2, Eq. (14)] The triangle inequality in Eq. (14) is not valid as written. It bounds ||G(u) - G_DMD(u)|| by ||G(u) - G(u_r)|| + ||G_DMD(u_r) - G_DMD(u)||, but inserting u_r requires also the middle term ||G(u_r) - G_DMD(u_r)||, which equals ||G(u_r) - H(u_r, Phi_r(u_r), Phi_r(u_r)^T u_r)||. This is the neural-operator approximation error at the rank-r projection. The Lipschitz assumptions on G and H and the Eckart-Young theorem do not control it. Taking u = u_r (so epsilon = 0) and H identically zero, which satisfies the Lipschitz assumption on H, makes the theorem assert ||G(u)|| <= 0 for an arbitrary nonzero G, so the stated (L_G + 2 L_H) epsilon bound is false as stated.
- [Sections 2.4.1-2.4.2 and Algorithm 2] The object analyzed in Theorem 1 is not the object implemented. The theorem defines G_DMD(u) = H(u, Phi_r(u), Phi_r(u)^T u) using the rank-r SVD of the input u, whereas Algorithm 2 computes DMD modes and dynamics once from the training snapshots (step 6) and then uses those fixed features m and d for all training and test predictions (steps 14 and 23). The DMD modes from Algorithm 1 are Phi = X' V_r Sigma_r^{-1} W, which are not the left singular vectors Phi_r(u) and need not be orthogonal, and the dynamics are eigenvalues rather than Phi_r(u)^T u. Consequently, even a corrected version of the theorem would not apply to the reported experiments, and the test losses do not measure generalization to genuinely new inputs.
- [Section 3.4 and Abstract] The abstract's claim of high reconstruction accuracy relative to DeepONet and FNO is not supported by the reported experiments. Section 3.4 states that plots of train and test loss for each model are provided, but no numerical results for DeepONet or FNO are given, and the content of Figures 9-10 is not discussed quantitatively. Tables 2, 4, and 6 contain only the proposed model's own losses. Without comparative MSE or relative L2 errors on a common test set, the central empirical claim cannot be evaluated.
- [Section 5] The conclusion contains a truncated sentence, 'achieving 0.8-2.1', with no units, no definition of the metric, and no comparison baseline. This is the only quantitative accuracy statement in the conclusion and it is incomplete, so it provides no support for the paper's effectiveness claim.
minor comments (5)
- [References] References [4] and [22] are the same work and should not be duplicated.
- [Algorithm 2] The symbol N_train is used both for the number of training epochs and for the size of the training split; these should be given distinct names.
- [Equation (11)] The inputs m_0,...,m_n, d_0,...,d_k, u_1,...,u_m in Eq. (11) are never defined, and the transition to the compact form in Eq. (12) is not explained.
- [Section 3 and Tables 2, 4, 6] The text says metrics are MSE and maximum absolute error, but the tables report only a scalar 'Loss'; the precise loss definition, normalization, and test-set aggregation should be stated.
- [Section 2.4.3] The layer counts, widths, activation functions, and DMD rank selection used in the experiments are not specified, which is insufficient for reproducibility despite the provided repository link.
Circularity Check
No circular reduction; Theorem 1 has an invalid proof, not a circular one, and the only self-citation (patent [43]) is not load-bearing.
full rationale
Walking the claimed derivation chain, the DMD features in Algorithm 2 step 6 are computed from the training snapshots and then fed into the branch/trunk network, which is a standard two-stage operator-learning pipeline rather than a fitted parameter renamed as a prediction: the reported test losses are on held-out grid points and the DMD representation is fixed before training. The only first-principles claim, Theorem 1 in Section 2.4.2, is not circular: G_DMD is defined as H(u, Φ_r(u), Φ_r(u)^T u) and the proof attempts to bound it from Lipschitz assumptions plus Eckart-Young, so the conclusion is not identical to an input by construction. However, the proof has a genuine gap: the triangle inequality in Eq. (14) omits the middle term ||G(u_r) - G_DMD(u_r)||, and the stated bound is false for H ≡ 0 with u = u_r; that is a correctness error, not a circularity. The abstract and Section 3.4 promise a comparative analysis against DeepONet and FNO, but this version reports no baseline tables, which is missing external evidence rather than circular reasoning. The only self-citation is the software registration patent [43], mentioned in the introduction and not used to justify any premise; accordingly the score is 2 at most.
Assumptions & free parameters
free parameters (5)
- DMD rank r =
10
- Number of DMD modes s =
not stated
- Learning rate eta =
not stated
- Regularization coefficient lambda =
not stated
- Network widths and depth =
not stated
assumptions (5)
- standard math Existence of optimal rank-r SVD approximation u_r with error epsilon
- domain assumption Solution operator G is L_G-Lipschitz
- ad hoc to paper Neural network H is L_H-Lipschitz in all inputs
- domain assumption DMD modes and dynamics are sufficient to determine the solution operator
- domain assumption Finite difference generators produce accurate ground truth
Cite this review
Pith. "Pith review of A Neural Operator based on Dynamic Mode Decomposition." pith.science (2026). https://pith.science/paper/DXMT35VX
@misc{pith2026250701117,
author = {Pith},
title = {Pith review of: A Neural Operator based on Dynamic Mode Decomposition},
year = {2026},
howpublished = {\url{https://pith.science/paper/DXMT35VX}},
note = {Machine review of arXiv:2507.01117}
}
read the original abstract
The scientific computation methods development in conjunction with artificial intelligence technologies remains a hot research topic. Finding a balance between lightweight and accurate computations is a solid foundation for this direction. The study presents a neural operator based on the dynamic mode decomposition algorithm (DMD), mapping functional spaces, which combines DMD and deep learning (DL) for spatiotemporal processes efficient modeling. Solving PDEs for various initial and boundary conditions requires significant computational resources. The method suggested automatically extracts key modes and system dynamics using them to construct predictions, reducing computational costs compared to traditional numerical methods. The approach has demonstrated its efficiency through comparative analysis of performance with closest analogues DeepONet and FNO in the heat equation, Laplaces equation, and Burgers equation solutions approximation, where it achieves high reconstruction accuracy.
Reference graph
Works this paper leans on
-
[1]
Kovachki, N., Li, Z., Liu, B., Azizzadenesheli, K., Bhattacharya, K., Stuart, A., Anandkumar, A., ”Neural operator: Learning maps between function spaces with applications to PDEs,”Journal of Machine Learning Research, vol. 24, pp. 1–97, 2023
work page 2023
-
[2]
Hao, Z., Wang, Z., Su, H., Ying, C., Dong, Y., Liu, S., Cheng, Z., Song, J., Zhu, J., ”GNOT: A general neural operator transformer for operator learning,” In: International Conference on Machine Learning, pp. 12556–12569, 2023
work page 2023
-
[3]
Azizzadenesheli, K., Kovachki, N., Li, Z., Liu-Schiaffini, M., Kossaifi, J., Anand- kumar, A., ”Neural operators for accelerating scientific simulations and design,” Nature Reviews Physics, vol. 6, pp. 320–328, 2024
work page 2024
-
[5]
Rafiq, M., Rafiq, G., Jung, H.-Y., Choi, G. S., ”SSNO: Spatio-Spectral Neural Operator for Functional Space Learning of Partial Differential Equations,”IEEE Access, vol. 10, pp. 15084–15095, 2022. doi: 10.1109/ACCESS.2022.3148401
-
[6]
Raonic, B., Molinaro, R., Rohner, T., Mishra, S., Bezenac, E., ”Convolutional neural operators,” In:ICLR 2023 Workshop on Physics for Machine Learning, 2023
work page 2023
-
[7]
Li, Z., Kovachki, N., Azizzadenesheli, K., Liu, B., Bhattacharya, K., Stuart, A., Anandkumar, A., ”Neural operator: Graph kernel network for partial differential equations,”arXiv preprint arXiv:2003.03485, 2020
arXiv 2003
-
[8]
Wei, M., Zhang, X., ”Super-resolution neural operator,” In:Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition, pp. 26 18247–18256, 2023
work page 2023
-
[9]
Rahman, M., Ross, Z., Azizzadenesheli, K., ”U-NO: U-shaped neural operators,” arXiv preprint arXiv:2204.11127, 2022
arXiv 2022
Show all 43 references
-
[10]
Li, Z., Kovachki, N., Azizzadenesheli, K., Liu, B., Stuart, A., Bhattacharya, K., Anandkumar, A., ”Multipole graph neural operator for parametric partial differential equations,” In:Advances in Neural Information Processing Systems, vol. 33, pp. 6755–6766, 2020
2020
-
[11]
Raonic, B., Molinaro, R., De Ryck, T., Rohner, T., Bartolucci, F., Alaifari, R., Mishra, S., B´ ezenac, E., ”Convolutional neural operators for robust and accurate learning of PDEs,”Advances in Neural Information Processing Systems, vol. 36, pp. 77187–77200, 2023
2023
-
[12]
1–8, 2024
Michalowska, K., Goswami, S., Karniadakis, G., Riemer-Sørensen, S., ”Neural operator learning for long-time integration in dynamical systems with recurrent neural networks,” In:2024 International Joint Conference on Neural Networks (IJCNN), pp. 1–8, 2024
2024
-
[13]
Yang, Y., Gao, A., Castellanos, J., Ross, Z., Azizzadenesheli, K., Clayton, R., ”Seismic wave propagation and inversion with neural operators,”The Seismic Record, vol. 1, pp. 126–134, 2021
2021
-
[14]
Zhang, Z., ”ModNO: Multi-operator learning with distributed neural operators,” Computer Methods in Applied Mechanics and Engineering, vol. 431, p. 117229, 2024
2024
-
[15]
Tran, A., Mathews, A., Xie, L., Ong, C., ”Factorized Fourier neural operators,” arXiv preprint arXiv:2111.13802, 2021
2021 arXiv
-
[16]
Kovachki, N., Lanthaler, S., Mishra, S., ”On universal approximation and error bounds for Fourier neural operators,”Journal of Machine Learning Research, vol. 22, pp. 1–76, 2021
2021
-
[17]
Hao, W., Liu, X., Yang, Y., ”Newton informed neural operator for solving nonlinear partial differential equations,” In:Advances in Neural Information Processing Systems, vol. 37, pp. 120832–120860, 2024
2024
-
[18]
Lu, L., Jin, P., Karniadakis, G., ”Deeponet: Learning nonlinear operators for identifying differential equations based on the universal approximation theorem of operators,”arXiv preprint arXiv:1910.03193, 2019
1910 arXiv
-
[19]
Lu, L., Jin, P., Pang, G., Zhang, Z., Karniadakis, G., ”Learning nonlinear opera- tors via DeepONet based on the universal approximation theorem of operators,” Nature Machine Intelligence, vol. 3, pp. 218–229, 2021. 27
2021
-
[20]
Jin, P., Meng, S., Lu, L., ”MIONet: Learning multiple-input operators via tensor product,”SIAM Journal on Scientific Computing, vol. 44, pp. A3490–A3514, 2022
2022
-
[21]
Yin, M., Charon, N., Brody, R., Lu, L., Trayanova, N., Maggioni, M., ”Dimon: Learning solution operators of partial differential equations on a diffeomorphic family of domains,”arXiv preprint arXiv:2402.07250, 2024
2024 arXiv
-
[22]
Sirota, D.D., Gushchin, K.A., Khan, S.A., Kostikov, S.L., Butov, K.A., ”Neu- ral operators for hydrodynamic modeling of underground gas storage facili- ties,”Russian Technological Journal, vol. 12, no. 6, pp. 102–112, 2024. doi: 10.32362/2500-316X-2024-12-6-102-112. EDN: YBOYBL
2024 doi
-
[23]
Li, Z., Huang, D., Liu, B., Anandkumar, A., ”Fourier neural operator with learned deformations for PDEs on general geometries,”Journal of Machine Learning Research, vol. 24, pp. 1–26, 2023
2023
-
[24]
Tripura, T., Chakraborty, S., ”Wavelet neural operator: a neural operator for parametric partial differential equations,”arXiv preprint arXiv:2205.02191, 2022
2022 arXiv
-
[25]
Tripura, T., Chakraborty, S., ”Wavelet neural operator for solving parametric partial differential equations in computational mechanics problems,”Computer Methods in Applied Mechanics and Engineering, vol. 404, p. 115783, 2023
2023
-
[26]
Cai, S., Mao, Z., Wang, Z., Yin, M., Karniadakis, G., ”Physics-informed neural networks (PINNs) for fluid mechanics: A review,”Acta Mechanica Sinica, vol. 37, pp. 1727–1738, 2021
2021
-
[27]
Rasht-Behesht, M., Huber, C., Shukla, K., Karniadakis, G., ”Physics-informed neural networks (PINNs) for wave propagation and full waveform inversions,” Journal of Geophysical Research: Solid Earth, vol. 127, p. e2021JB023120, 2022
2022
-
[28]
Wang, S., Yu, X., Perdikaris, P., ”When and why PINNs fail to train: A neu- ral tangent kernel perspective,”Journal of Computational Physics, vol. 449, p. 110768, 2022
2022
-
[29]
Yu, B., Others, ”The deep Ritz method: a deep learning-based numerical algo- rithm for solving variational problems,”Communications in Mathematics and Statistics, vol. 6, pp. 1–12, 2018
2018
-
[30]
Sirignano, J., Spiliopoulos, K., ”DGM: A deep learning algorithm for solving partial differential equations,”Journal of Computational Physics, vol. 375, pp. 1339–1364, 2018
2018
-
[31]
Cao, Q., Goswami, S., Karniadakis, G., ”Laplace neural operator for solving differential equations,”Nature Machine Intelligence, vol. 6, pp. 631–640, 2024. 28
2024
-
[32]
Xiong, W., Huang, X., Zhang, Z., Deng, R., Sun, P., Tian, Y., ”Koopman neu- ral operator as a mesh-free solver of non-linear partial differential equations,” Journal of Computational Physics, vol. 513, p. 113194, 2024
2024
-
[33]
Lu, J., Jiang, J., Bai, Y., ”Deep Embedding Koopman Neural Operator Based Nonlinear Flight Training Trajectory Prediction Approach,”Mathematics, vol. 12, p. 2162, 2024
2024
-
[34]
Iwata, T., Kawahara, Y., ”Neural dynamic mode decomposition for end-to-end modeling of nonlinear dynamics,”Journal of Computational Dynamics, vol. 10, pp. 268–280, 2023
2023
-
[35]
Tu, J., ”Dynamic mode decomposition: Theory and applications,”Princeton University, 2013
2013
-
[36]
Proctor, J., Brunton, S., Kutz, J., ”Dynamic mode decomposition with control,” SIAM Journal on Applied Dynamical Systems, vol. 15, pp. 142–161, 2016
2016
-
[37]
Schmid, P., ”Dynamic mode decomposition and its variants,”Annual Review of Fluid Mechanics, vol. 54, pp. 225–254, 2022
2022
-
[38]
Chen, S., Liu, Z., Zhang, W., Yang, J., ”A hard-constraint wide-body physics- informed neural network model for solving multiple cases in forward problems for partial differential equations,”Applied Sciences, vol. 14, p. 189, 2023
2023
-
[39]
Zhang, Z., Wang, Q., Zhang, Y. et al., ”Physics-informed neural networks with hybrid Kolmogorov-Arnold network and augmented Lagrangian function for solving partial differential equations,”Scientific Reports, vol. 15, p. 10523, 2025. doi:10.1038/s41598-025-92900-1
2025 doi
-
[40]
Li, Y., Gao, W., Ying, S., ”RBF-Assisted Hybrid Neural Network for Solving Partial Differential Equations,”Mathematics, vol. 12, p. 1617, 2024
2024
-
[41]
Wang, J., Li, Y., Wu, A., Chen, Z., Huang, J., Wang, Q., Liu, F., ”Multi-Step Physics-Informed Deep Operator Neural Network for Directly Solving Partial Differential Equations,”Applied Sciences, vol. 14, p. 5490, 2024
2024
-
[42]
Sun, K., Feng, X., ”A second-order network structure based on gradient enhanced physics-informed neural networks for solving parabolic partial differ- ential equations,”Entropy, vol. 25, p. 674, 2023
2023
-
[43]
2025663626; Rospatent Federal Service on Intellectual Property: Moscow, Russia, 2025
Sakovich, N.D., Aksenov, D.A., Pleshakova, E.S., Gataullin, S.T., ”A neural operator based on dynamic mode decomposition analysis for approximation of partial differential equations,” Certificate of State Registration of Computer Program No. 2025663626; Rospatent Federal Servi...
2025
-
[44]
Eckart, C., Young, G., ”The approximation of one matrix by another of lower rank,”Psychometrika, vol. 1, pp. 211–218, 1936. 30
1936
Reviewed August 6, 2026 · model on record in the stance chip above.
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