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arxiv: 2607.02194 · v1 · pith:5RRX4GFHnew · submitted 2026-07-02 · 💻 cs.LG · cs.NA· math.NA· math.OC· physics.comp-ph

An Optimisation Framework for the Well-Conditioned Training of Physics-Informed Neural Networks

Pith reviewed 2026-07-03 16:51 UTC · model grok-4.3

classification 💻 cs.LG cs.NAmath.NAmath.OCphysics.comp-ph
keywords physics-informed neural networksGauss-Newton optimizationill-conditioned loss landscapesPDE solverssecond-order methodsnumerical accuracysketching
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The pith

DSGNAR optimization reaches relative errors of 3e-16 for physics-informed neural networks on PDEs.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper presents DSGNAR as a second-order method that pairs a doubly-sketched Gauss-Newton approximation with an adaptive control of regularization and step length. This targets the severe ill-conditioning that has limited PINN accuracy on nonlinear, chaotic, multi-scale, and high-dimensional PDEs. The approach yields relative L2 errors down to 3 times 10 to the minus 16 in double precision, gains of five to eight orders of magnitude over prior results on Burgers and Poisson problems, and near round-off solutions in single precision within seconds. A reader would care because it narrows the accuracy gap between neural solvers and classical numerical methods while preserving speed.

Core claim

DSGNAR couples a doubly-sketched Gauss-Newton model with a novel strategy that carefully controls both regularisation and step length. Across nonlinear, chaotic, multi-scale, high-dimensional, and Navier-Stokes problems the framework attains relative L2 errors as low as 3 times 10 to the minus 16 in double precision, improves contemporary results by five orders of magnitude on Burgers equation and eight orders on a high-dimensional Poisson problem, and remains markedly faster. In single precision, solutions at the limit of round-off error are obtained very quickly, for example Burgers equation to relative L2 of 4.75 times 10 to the minus 7 in under ten seconds. The framework is robust to arc

What carries the argument

Doubly-Sketched Gauss-Newton with Adaptive Ratio (DSGNAR), which approximates the Hessian via sketching and adaptively tunes regularization and step length to stabilize the ill-conditioned PINN loss landscape.

If this is right

  • PINN solutions to standard nonlinear PDEs can reach limits of double-precision round-off.
  • High-dimensional Poisson problems become solvable to eight orders better accuracy than prior PINN methods.
  • Single-precision training can still deliver near-round-off results on Burgers-type equations in seconds.
  • The same framework works across varied network architectures without retuning.
  • Training time remains lower than competing first-order or other second-order PINN optimizers while achieving the accuracy gains.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • The sketching-plus-adaptive-ratio pattern may transfer to other ill-conditioned scientific machine-learning tasks beyond PINNs.
  • If the method scales to larger 3-D time-dependent Navier-Stokes cases, it could support real-time surrogate modeling in engineering workflows.
  • The observed robustness to arithmetic precision suggests the framework could be useful on hardware with limited floating-point support.

Load-bearing premise

The assumption that the doubly-sketched Gauss-Newton model combined with the adaptive ratio strategy will reliably control the severe ill-conditioning of the PINN loss landscape across the tested problem classes without introducing new instabilities or requiring problem-specific tuning.

What would settle it

A run on the canonical Burgers equation following the paper's stated procedure and hyperparameters that yields relative L2 error larger than 10 to the minus 10 in double precision.

Figures

Figures reproduced from arXiv: 2607.02194 by Coralia Cartis, Joseph Webb, Sadok Jerad.

Figure 1
Figure 1. Figure 1: A representative high-accuracy solve with our framework. The viscous Burgers’ equation (Section Ap￾pendix C.1) solved in double precision with a SIREN of dθ = 11,285 trainable parameters and sketch size s = 4,000. (a) The recovered solution uθ(x, t), including the sharp internal layer that forms near x = 0. (b) The training loss L, driven below 10−29 in 331 iterations. (c) The relative ℓ2 error against the… view at source ↗
Figure 2
Figure 2. Figure 2: Comparison of the full Jacobian (a) with the corresponding doubly-sketched Jacobian (b), using CountSketch and SRCT, for an early iteration solving Burgers’ equation. The full Jacobian has NP +NI = 215 + 214 residuals, and 1447 trainable parameters. The doubly-sketched Jacobian is a square of size s = 700, with clear isotropic structure. dimension dθ, we therefore use a random subspace embedding, compressi… view at source ↗
Figure 3
Figure 3. Figure 3: The selection of optimisation step. The model ∆(ϱ) is built from probe triplets (∆i, λi, ϱi) which are geometri￾cally spaced around the trust-region radius ∆k. The next iteration’s ∆k+1 is selected by interpolating the model at the target ratio ϱ. The regularisation corresponding to the target ratio ϱ is chosen as λk which determines the optimisation step, as in Equation (20) (which is subsequently lifted … view at source ↗
Figure 4
Figure 4. Figure 4: Ablation study on the choice of target ratio ϱ, with a comparison against a two-stage approach, when solving Burgers’ equation in double precision. We show that smaller choices of the target ratio ϱ provide smaller values of regularisation λ, and consequently higher-quality solutions. This performance comes at the cost of more iterations; however, the two-stage approach shows that if ϱ switches to a high v… view at source ↗
read the original abstract

Physics-informed neural networks (PINNs) have emerged as a promising route to solve partial differential equations, yet they have struggled to reach the precision of classical solvers. The obstacle is increasingly understood to be one of optimisation, owing to the severely ill-conditioned loss landscape. We present $\textbf{DSGNAR}$: Doubly-Sketched Gauss-Newton with Adaptive Ratio, a scalable second-order optimisation framework that confronts this ill-conditioning and, in doing so, obtains unprecedented accuracy and speed. $\textbf{DSGNAR}$ couples a doubly-sketched Gauss-Newton model with a novel strategy that carefully controls both regularisation and step length. Across a suite of problems spanning nonlinear, chaotic, multi-scale, high-dimensional, and Navier-Stokes, the framework greatly improves on the state of the art: able to attain relative $\ell_2$ errors as low as $3\times10^{-16}$ in double precision, improve contemporary results by five orders of magnitude on the canonical Burgers' equation, and as much as eight orders on a high-dimensional Poisson problem, while remaining markedly faster. We further show that, in single precision, solutions at the limit of round-off error can be obtained very quickly: Burgers' equation to $\ell_2^{\text{rel}} = 4.75 \times 10^{-7}$ in under ten seconds. The framework is also robust to the choice of architecture, arithmetic precision, and initial hyperparameters. The code is available at https://www.github.com/wephy/physics-informed-neural-networks

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 2 minor

Summary. The manuscript introduces DSGNAR, a doubly-sketched Gauss-Newton optimization framework augmented with an adaptive ratio strategy for regularization and step-length control. It targets the severely ill-conditioned loss landscapes of PINNs and reports relative ℓ₂ errors down to 3×10^{-16} in double precision, five-order-of-magnitude gains on Burgers' equation, eight-order gains on a high-dimensional Poisson problem, round-off-limited accuracy in single precision within seconds, and robustness across architectures, precisions, and initial hyperparameters. Code is released.

Significance. If the empirical claims are supported by the necessary ablations, error-bar statistics, and evidence that the adaptive rule generalizes without implicit problem-dependent tuning, the work would constitute a notable advance in PINN optimization, potentially rendering PINNs competitive with classical solvers on accuracy while retaining their flexibility. The open-source code strengthens reproducibility.

major comments (2)
  1. [Abstract and §4] Abstract and §4 (Experiments): the reported accuracy numbers (e.g., 3×10^{-16}, five- and eight-order improvements) are presented without error-bar analysis, ablation isolating the doubly-sketched Gauss-Newton component from the adaptive-ratio component, or verification that the same hyper-parameters were not re-used in the performance metric. These omissions are load-bearing for the central claim that the combined framework reliably controls ill-conditioning.
  2. [§3.2] §3.2 (Adaptive Ratio Strategy): the adaptation rule is asserted to control regularization and step length robustly across nonlinear/chaotic/multi-scale/high-dimensional/Navier-Stokes problems without new instabilities or problem-specific tuning, yet the manuscript supplies neither a convergence analysis of the ratio thresholds nor failure-mode ablations. This directly underpins the robustness claim.
minor comments (2)
  1. [Table 2] Table 2: the single-precision Burgers' timing result would be clearer if wall-clock time were reported alongside iteration count.
  2. [§2] Notation in §2: the distinction between the two sketching matrices should be made explicit at first use to avoid ambiguity in later equations.

Simulated Author's Rebuttal

2 responses · 1 unresolved

We thank the referee for the constructive comments on our manuscript. We address each major comment point-by-point below, agreeing where revisions are needed to strengthen the empirical support for our claims.

read point-by-point responses
  1. Referee: [Abstract and §4] Abstract and §4 (Experiments): the reported accuracy numbers (e.g., 3×10^{-16}, five- and eight-order improvements) are presented without error-bar analysis, ablation isolating the doubly-sketched Gauss-Newton component from the adaptive-ratio component, or verification that the same hyper-parameters were not re-used in the performance metric. These omissions are load-bearing for the central claim that the combined framework reliably controls ill-conditioning.

    Authors: We agree that the central claims would be strengthened by error-bar statistics, component-wise ablations, and explicit clarification on hyperparameter usage. The current manuscript reports point estimates from individual runs without statistical error bars and does not include dedicated ablations that isolate the doubly-sketched Gauss-Newton step from the adaptive-ratio mechanism. Hyperparameters were chosen once on a small validation set and then held fixed for all reported comparisons; they were not re-tuned to the final performance metric. In revision we will add (i) error bars computed over multiple random initializations, (ii) ablation tables that disable each component in turn, and (iii) a short subsection confirming the fixed-hyperparameter protocol. These additions directly address the load-bearing concerns. revision: yes

  2. Referee: [§3.2] §3.2 (Adaptive Ratio Strategy): the adaptation rule is asserted to control regularization and step length robustly across nonlinear/chaotic/multi-scale/high-dimensional/Navier-Stokes problems without new instabilities or problem-specific tuning, yet the manuscript supplies neither a convergence analysis of the ratio thresholds nor failure-mode ablations. This directly underpins the robustness claim.

    Authors: The adaptive-ratio rule is presented as an empirical heuristic whose thresholds were observed to work across the tested suite. The manuscript contains no theoretical convergence analysis of the ratio thresholds, nor systematic failure-mode ablations that deliberately stress the rule outside the reported problem classes. We will add failure-mode experiments (e.g., extreme initializations, deliberately poor ratio thresholds, and additional Navier-Stokes variants) to the revised §3.2 and §4. A formal convergence analysis, however, lies outside the empirical scope of the present work. revision: partial

standing simulated objections not resolved
  • A theoretical convergence analysis of the adaptive-ratio thresholds; this would require substantial new mathematical derivations beyond the empirical focus of the manuscript.

Circularity Check

0 steps flagged

No circularity: framework presented as independent optimisation method

full rationale

The abstract and description present DSGNAR as a general second-order framework (doubly-sketched Gauss-Newton plus adaptive ratio) whose performance claims are outcomes on external benchmark PDE problems. No equations, derivations, or claims reduce a reported accuracy or prediction to a fitted parameter or self-citation by construction. The method is described as robust across architectures and precisions without invoking prior self-authored uniqueness theorems or ansatzes that would make the central result tautological. This is the common case of a self-contained proposal evaluated against independent benchmarks.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

Abstract-only review; no explicit free parameters, axioms, or invented entities can be extracted beyond the implicit modeling choice that the sketched Gauss-Newton curvature approximation plus adaptive control suffices for the ill-conditioned PINN loss.

pith-pipeline@v0.9.1-grok · 5828 in / 1152 out tokens · 17518 ms · 2026-07-03T16:51:30.326078+00:00 · methodology

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