REVIEW 4 minor 1 cited by
Multilevel Adaptive-Rank Methods for Linear and Nonlinear Systems in the Hierarchical Tucker Format
T0 review · 0 major / 4 minor · reviewed 2026-06-26 · grok-4.3
Pith's one-line read Multilevel adaptive-rank methods in the Hierarchical Tucker format provide robust preconditioners for high-dimensional linear and nonlinear systems.
desk verdict This paper extends the Ballani-Grasedyck projection and multigrid ideas into adaptive-rank Hierarchical Tucker preconditioners, then wraps them in inexact Newton for nonlinear high-dimensional systems, with numerical tests on model problems. 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
Multilevel adaptive-rank preconditioners constructed by extending the projection method and adapting geometric multigrid to the Hierarchical Tucker tensor format.
What would settle it
Observing that the tensor ranks grow uncontrollably or that the preconditioner fails to reduce iteration counts on the tested model problems would disprove the effectiveness claim.
Extended reading notes
Core claim
The central claim is that multilevel adaptive-rank strategies yield robust and scalable preconditioners for linear and nonlinear systems in the Hierarchical Tucker format, as demonstrated by their convergence behavior and efficiency on model problems.
Load-bearing premise
The solutions of the target PDEs admit sufficiently accurate low-rank approximations in the Hierarchical Tucker format without prohibitive rank growth during the iterative process.
Editorial extensions
If this is right
- The methods handle both linear and nonlinear equations effectively.
- They maintain efficiency and accuracy through adaptive rank control during iteration.
- Multigrid serves as a preconditioner rather than a standalone solver in this low-rank context.
- The framework scales to high-dimensional problems where direct methods would be prohibitive.
Reading between the lines
- These techniques could extend to other tensor formats if the hierarchical structure is preserved.
- Testing on more complex real-world PDEs would reveal if rank growth remains manageable.
- The inexact Newton integration suggests potential for optimization problems beyond PDEs.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The manuscript develops multilevel adaptive-rank iterative methods for linear and nonlinear systems from high-dimensional PDEs in the Hierarchical Tucker format. It extends the Ballani-Grasedyck projection method to support flexible preconditioning, adapts geometric multigrid ideas to construct multilevel preconditioners in the low-rank setting, and embeds the resulting solvers in an inexact Newton framework for nonlinear problems. Numerical experiments on model problems are used to illustrate convergence behavior and computational efficiency, with the central claim that these strategies produce robust and scalable preconditioners.
Significance. If the reported numerical behavior holds under the stated assumptions on rank growth, the work offers a practical route to preconditioned solvers for high-dimensional problems that avoids the full curse of dimensionality. The shift in emphasis from multigrid as a standalone solver to its use as a robust preconditioner within an adaptive-rank framework is a useful distinction, and the integration with inexact Newton methods broadens applicability to nonlinear cases.
minor comments (4)
- [Abstract] Abstract: the phrase 'a range of model problems' is too vague; explicitly naming the linear and nonlinear PDEs (e.g., Poisson, reaction-diffusion) would allow readers to judge the breadth of the claimed robustness.
- [§2] §2 (method extension): the modifications made to the Ballani-Grasedyck projection operator to enable 'flexible preconditioning' are described at a high level; a short algorithmic outline or pseudocode would clarify the differences from the original reference [6].
- [Numerical results] Numerical results section: tables of iteration counts and CPU times should include at least one baseline (e.g., non-adaptive fixed-rank HT or standard AMG) so that the advantage of the multilevel adaptive-rank strategy can be quantified rather than asserted qualitatively.
- [§4] §4 (inexact Newton): the choice of inner tolerance for the linear solves is stated but not justified with respect to the outer Newton convergence; a brief remark on how the tolerance is adapted would strengthen the description.
Simulated Author's Rebuttal
We thank the referee for the positive assessment of our work on multilevel adaptive-rank iterative methods for high-dimensional systems in the Hierarchical Tucker format and for recommending minor revision. We are pleased that the distinction between using multigrid as a preconditioner rather than a standalone solver, along with the extension to nonlinear problems via inexact Newton, was noted as useful.
Circularity Check
No significant circularity
full rationale
The paper describes algorithmic extensions of prior projection methods, construction of multilevel preconditioners adapted from geometric multigrid, and their use inside an inexact Newton framework, followed by numerical evaluation on model problems. No equations, parameter fits, or derivations are shown that reduce a claimed prediction or result to the inputs by construction. The cited reference [6] is external work by different authors. The central claims rest on reported convergence behavior and efficiency from experiments, which are independent of any self-referential definition or fitted-input renaming. This is the standard non-circular structure for a numerical methods paper.
Assumptions & free parameters
Cite this review
Pith. "Pith review of Multilevel Adaptive-Rank Methods for Linear and Nonlinear Systems in the Hierarchical Tucker Format." pith.science (2026). https://pith.science/paper/QSX4MPZJ
@misc{pith2026260621750,
author = {Pith},
title = {Pith review of: Multilevel Adaptive-Rank Methods for Linear and Nonlinear Systems in the Hierarchical Tucker Format},
year = {2026},
howpublished = {\url{https://pith.science/paper/QSX4MPZJ}},
note = {Machine review of arXiv:2606.21750}
}
read the original abstract
We develop multilevel adaptive-rank iterative methods for the solution of linear and nonlinear systems arising from high-dimensional partial differential equations. Our contributions are threefold. First, we extend the projection method of Ballani and Grasedyck [6] to enable flexible preconditioning of high-dimensional linear systems in low-rank tensor formats. Second, we construct multilevel preconditioning strategies by adapting geometric multigrid methods to the low-rank setting. In contrast to prior work, which primarily employs multigrid as a standalone solver, we emphasize its role as an efficient and robust preconditioner. Third, we integrate these techniques within an inexact Newton framework for the solution of nonlinear systems. The proposed methods are evaluated on a range of model problems, including both linear and nonlinear equations, to assess their convergence behavior and computational efficiency. The results demonstrate that multilevel adaptive-rank strategies yield robust and scalable preconditioners, providing effective solvers for high-dimensional problems in low-rank formats.
Figures
Forward citations
Cited by 1 Pith paper
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A Mass, Momentum, and Energy Conserving Semi-Lagrangian Adaptive-Rank (SLAR) Method for the Vlasov-Poisson System
SLAR method with implicit LoMaC correction and adaptive-weight projection conserves mass, momentum, and energy for the Vlasov-Poisson system up to 2D-2V while retaining large time steps and high-order accuracy.
Reference graph
Works this paper leans on
-
[1]
Psychometrika , volume =
Some mathematical notes on three-mode factor analysis , author =. Psychometrika , volume =
-
[2]
SIAM Journal on Matrix Analysis and Applications , volume =
A multilinear singular value decomposition , author =. SIAM Journal on Matrix Analysis and Applications , volume =. 2000 , publisher =
2000
-
[3]
Quantum Information & Computation , volume =
Matrix product state representations , author =. Quantum Information & Computation , volume =. 2007 , publisher =
2007
-
[4]
SIAM Review , volume =
Tensor decompositions and applications , author =. SIAM Review , volume =
-
[5]
Journal of Fourier Analysis and Applications , volume =
A new scheme for the tensor representation , author =. Journal of Fourier Analysis and Applications , volume =
-
[6]
SIAM Journal on Matrix Analysis and Applications , volume =
Hierarchical singular value decomposition of tensors , author =. SIAM Journal on Matrix Analysis and Applications , volume =
-
[7]
SIAM Journal on Scientific Computing , volume =
Tensor-train decomposition , author =. SIAM Journal on Scientific Computing , volume =. 2011 , publisher =
2011
-
[8]
and Eisenstat, Stanley C
Dembo, Ron S. and Eisenstat, Stanley C. and Steihaug, Trond , journal =. Inexact. 1982 , publisher =
1982
Show all 88 references
-
[9]
A flexible inner-outer preconditioned
Saad, Youcef , journal =. A flexible inner-outer preconditioned. 1993 , publisher =
1993
-
[10]
Kelley, C. T. , title =. 1995 , doi =
1995
-
[11]
and Walker, Homer F
Eisenstat, Stanley C. and Walker, Homer F. , journal =. Choosing the forcing terms in an inexact. 1996 , publisher =
1996
-
[12]
2000 , edition =
A Multigrid Tutorial , author =. 2000 , edition =
2000
-
[13]
2000 , publisher =
Multigrid , author =. 2000 , publisher =
2000
-
[14]
and Keyes, David E
Knoll, Dana A. and Keyes, David E. , journal =. 2004 , publisher =
2004
-
[15]
SIAM Journal on Scientific Computing , volume =
Multigrid accelerated tensor approximation of function related multidimensional arrays , author =. SIAM Journal on Scientific Computing , volume =. 2009 , publisher =
2009
-
[16]
and Oseledets, Ivan V
Dolgov, Sergey V. and Oseledets, Ivan V. , journal =. Solution of linear systems and matrix inversion in the. 2012 , publisher =
2012
-
[17]
and Khoromskij, Boris N
Dolgov, Sergey V. and Khoromskij, Boris N. and Oseledets, Ivan V. , journal =. Fast solution of parabolic problems in the. 2012 , publisher =
2012
-
[18]
Numerical Linear Algebra with Applications , volume =
A projection method to solve linear systems in tensor format , author =. Numerical Linear Algebra with Applications , volume =. 2013 , publisher =
2013
-
[19]
SIAM Journal on Scientific Computing , volume =
Alternating minimal energy methods for linear systems in higher dimensions , author =. SIAM Journal on Scientific Computing , volume =. 2014 , publisher =
2014
-
[20]
Multilevel preconditioning and low-rank tensor iteration for space--time simultaneous discretizations of parabolic
Andreev, Roman and Tobler, Christine , journal =. Multilevel preconditioning and low-rank tensor iteration for space--time simultaneous discretizations of parabolic. 2015 , publisher =
2015
-
[21]
Kormann, Katharina , journal =. A semi-. 2015 , publisher =
2015
-
[22]
Computing and Visualization in Science , volume =
Solution of linear systems in high spatial dimensions , author =. Computing and Visualization in Science , volume =. 2015 , publisher =
2015
-
[23]
SIAM Journal on Scientific Computing , volume =
A preconditioned low-rank projection method with a rank-reduction scheme for stochastic partial differential equations , author =. SIAM Journal on Scientific Computing , volume =. 2017 , publisher =
2017
-
[25]
Bollettino dell'Unione Matematica Italiana , volume =
Numerical solution of a class of third order tensor linear equations , author =. Bollettino dell'Unione Matematica Italiana , volume =. 2020 , publisher =
2020
-
[26]
A parallel low-rank solver for the six-dimensional
Allmann-Rahn, Florian and Grauer, Rainer and Kormann, Katharina , journal =. A parallel low-rank solver for the six-dimensional. 2022 , publisher =
2022
-
[27]
Ye, Erika and Loureiro, Nuno F. G. , journal =. Quantum-inspired method for solving the. 2022 , publisher =
2022
-
[28]
A robust
Coulaud, Olivier and Giraud, Luc and Iannacito, Martina , journal =. A robust
-
[29]
PAMM , volume =
Computing tensor operator exponentials within low-rank tensor formats with application to the parameter-dependent multigrid method , author =. PAMM , volume =. 2023 , publisher =
2023
-
[30]
Journal of Scientific Computing , volume =
Implicit integration of nonlinear evolution equations on tensor manifolds , author =. Journal of Scientific Computing , volume =. 2023 , publisher =
2023
-
[31]
, journal =
Ye, Erika and Loureiro, Nuno F. , journal =. Quantized tensor networks for solving the. 2024 , publisher =
2024
-
[32]
Krylov-based adaptive-rank implicit time integrators for stiff problems with application to nonlinear
El Kahza, Hamad and Taitano, William and Qiu, Jing-Mei and Chac. Krylov-based adaptive-rank implicit time integrators for stiff problems with application to nonlinear. Journal of Computational Physics , volume =. 2024 , publisher =
2024
-
[33]
Journal of Computational Physics , volume =
A review of low-rank methods for time-dependent kinetic simulations , author =. Journal of Computational Physics , volume =. 2025 , publisher =
2025
-
[34]
Appelo, Daniel and Cheng, Yingda , year =. lr. 2503.03909 , archivePrefix =
-
[35]
Journal of Scientific Computing , volume =
Tensor network space-time spectral collocation method for solving the nonlinear convection diffusion equation , author =. Journal of Scientific Computing , volume =. 2025 , publisher =
2025
-
[36]
Electronic Transactions on Numerical Analysis , volume =
Operator-dependent prolongation and restriction for the parameter-dependent multigrid method using low-rank tensor formats , author =. Electronic Transactions on Numerical Analysis , volume =. 2025 , doi =
2025
-
[37]
and Guo, Wei and Qiu, Jing-Mei and Xiong, Tao , journal =
Sands, William A. and Guo, Wei and Qiu, Jing-Mei and Xiong, Tao , journal =. High-order adaptive rank integrators for multi-scale linear kinetic transport equations in the hierarchical. 2025 , publisher =
2025
-
[38]
Sands and Jing-Mei Qiu and Daniel Hayes and Nanyi Zheng , journal=
William A. Sands and Jing-Mei Qiu and Daniel Hayes and Nanyi Zheng , journal=. An adaptive-rank approach with greedy sampling for multi-scale. 2026 , publisher=
2026
-
[39]
and Hayes, Daniel and Christlieb, Andrew J
Zheng, Nanyi and Sands, William A. and Hayes, Daniel and Christlieb, Andrew J. and Qiu, Jing-Mei , year =. A semi-. 2510.24861 , archivePrefix =
-
[40]
Journal of Computational Physics , volume =
Sylvester-preconditioned adaptive-rank implicit time integrators for advection-diffusion equations with variable coefficients , author =. Journal of Computational Physics , volume =. 2025 , publisher =
2025
-
[41]
Computer Physics Communications , year =
A low-rank, high-order implicit-explicit integrator for three-dimensional convection-diffusion equations , author =. Computer Physics Communications , year =
-
[42]
2026 , eprint =
Multigroup thermal radiation transport with tensor trains , author =. 2026 , eprint =
2026
-
[43]
Dynamical
Wang, Geshuo and Hu, Jingwei , journal =. Dynamical. 2026 , publisher =
2026
-
[44]
Algorithm 941:
Kressner, Daniel and Tobler, Christine , journal =. Algorithm 941:. 2014 , publisher =
2014
-
[45]
Dougherty, J. P. , journal =. Model. 1964 , publisher =
1964
-
[46]
Acta Metallurgica , volume =
A microscopic theory for antiphase boundary motion and its application to antiphase domain coarsening , author =. Acta Metallurgica , volume =. 1979 , publisher =
1979
-
[47]
and MacDonald, William M
Rosenbluth, Marshall N. and MacDonald, William M. and Judd, David L. , journal =. 1957 , publisher =
1957
-
[48]
and Chac
Taitano, William T. and Chac. A mass, momentum, and energy conserving, fully implicit, scalable algorithm for the multi-dimensional, multi-species. Journal of Computational Physics , volume =. 2015 , publisher =
2015
-
[49]
D. Adak, M. E. Danis, D. P. Truong, K. . Rasmussen, and B. S. Alexandrov , Tensor network space-time spectral collocation method for solving the nonlinear convection diffusion equation , Journal of Scientific Computing, 103 (2025), p. 46
2025
-
[50]
S. M. Allen and J. W. Cahn , A microscopic theory for antiphase boundary motion and its application to antiphase domain coarsening , Acta Metallurgica, 27 (1979), pp. 1085--1095
1979
-
[51]
Allmann-Rahn, R
F. Allmann-Rahn, R. Grauer, and K. Kormann , A parallel low-rank solver for the six-dimensional Vlasov--Maxwell equations , Journal of Computational Physics, 469 (2022), p. 111562
2022
-
[52]
Andreev and C
R. Andreev and C. Tobler , Multilevel preconditioning and low-rank tensor iteration for space--time simultaneous discretizations of parabolic PDEs , Numerical Linear Algebra with Applications, 22 (2015), pp. 317--337
2015
-
[53]
Appelo and Y
D. Appelo and Y. Cheng , lr AA : Low-rank Anderson Acceleration , 2025
2025
-
[54]
Ballani and L
J. Ballani and L. Grasedyck , A projection method to solve linear systems in tensor format , Numerical Linear Algebra with Applications, 20 (2013), pp. 27--43
2013
-
[55]
W. L. Briggs, V. E. Henson, and S. F. McCormick , A Multigrid Tutorial , Society for Industrial and Applied Mathematics, Philadelphia, PA, 2 ed., 2000
2000
-
[56]
Coulaud, L
O. Coulaud, L. Giraud, and M. Iannacito , A robust GMRES algorithm in Tensor Train format , arXiv preprint arXiv:2210.14533, (2022)
2022
-
[57]
De Lathauwer, B
L. De Lathauwer, B. De Moor, and J. Vandewalle , A multilinear singular value decomposition , SIAM Journal on Matrix Analysis and Applications, 21 (2000), pp. 1253--1278
2000
-
[58]
A. S. Deshpande, P. D. Mullen, A. A. Gorodetsky, J. C. Dolence, C. D. Meyer, J. M. Miller, and L. F. Roberts , Multigroup thermal radiation transport with tensor trains , 2026
2026
-
[59]
S. V. Dolgov, B. N. Khoromskij, and I. V. Oseledets , Fast solution of parabolic problems in the Tensor Train / Quantized Tensor Train format with initial application to the Fokker--Planck equation , SIAM Journal on Scientific Computing, 34 (2012), pp. A3016--A3038
2012
-
[60]
S. V. Dolgov and I. V. Oseledets , Solution of linear systems and matrix inversion in the TT -format , SIAM Journal on Scientific Computing, 34 (2012), pp. A2718--A2739
2012
-
[61]
S. V. Dolgov and D. V. Savostyanov , Alternating minimal energy methods for linear systems in higher dimensions , SIAM Journal on Scientific Computing, 36 (2014), pp. A2248--A2271
2014
-
[62]
J. P. Dougherty , Model Fokker--Planck equation for a plasma and its solution , The Physics of Fluids, 7 (1964), pp. 1788--1799
1964
-
[63]
Einkemmer, K
L. Einkemmer, K. Kormann, J. Kusch, R. G. McClarren, and J.-M. Qiu , A review of low-rank methods for time-dependent kinetic simulations , Journal of Computational Physics, 538 (2025), p. 114191
2025
-
[64]
S. C. Eisenstat and H. F. Walker , Choosing the forcing terms in an inexact Newton method , SIAM Journal on Scientific Computing, 17 (1996), pp. 16--32
1996
-
[65]
El Kahza, J.-M
H. El Kahza, J.-M. Qiu, L. Chac \'o n, and W. Taitano , Sylvester-preconditioned adaptive-rank implicit time integrators for advection-diffusion equations with variable coefficients , Journal of Computational Physics, 543 (2025), p. 114377
2025
-
[66]
El Kahza, W
H. El Kahza, W. Taitano, J.-M. Qiu, and L. Chac \'o n , Krylov-based adaptive-rank implicit time integrators for stiff problems with application to nonlinear Fokker--Planck kinetic models , Journal of Computational Physics, 518 (2024), p. 113332
2024
-
[67]
Grasedyck , Hierarchical singular value decomposition of tensors , SIAM Journal on Matrix Analysis and Applications, 31 (2010), pp
L. Grasedyck , Hierarchical singular value decomposition of tensors , SIAM Journal on Matrix Analysis and Applications, 31 (2010), pp. 2029--2054
2010
-
[68]
Grasedyck, M
L. Grasedyck, M. Klever, C. L \"o bbert, and T. A. Werthmann , A parameter-dependent smoother for the multigrid method , arXiv preprint arXiv:2008.00927, (2020)
2008
-
[69]
Grasedyck and T
L. Grasedyck and T. A. Werthmann , Computing tensor operator exponentials within low-rank tensor formats with application to the parameter-dependent multigrid method , PAMM, 22 (2023), p. e202200093
2023
-
[70]
188--207
height 2pt depth -1.6pt width 23pt, Operator-dependent prolongation and restriction for the parameter-dependent multigrid method using low-rank tensor formats , Electronic Transactions on Numerical Analysis, 62 (2025), pp. 188--207
2025
-
[71]
Hackbusch , Solution of linear systems in high spatial dimensions , Computing and Visualization in Science, 17 (2015), pp
W. Hackbusch , Solution of linear systems in high spatial dimensions , Computing and Visualization in Science, 17 (2015), pp. 111--118
2015
-
[72]
Hackbusch and S
W. Hackbusch and S. K \"u hn , A new scheme for the tensor representation , Journal of Fourier Analysis and Applications, 15 (2009), pp. 706--722
2009
-
[73]
B. N. Khoromskij and V. Khoromskaia , Multigrid accelerated tensor approximation of function related multidimensional arrays , SIAM Journal on Scientific Computing, 31 (2009), pp. 3002--3026
2009
-
[74]
D. A. Knoll and D. E. Keyes , Jacobian-free Newton--Krylov methods: a survey of approaches and applications , Journal of Computational Physics, 193 (2004), pp. 357--397
2004
-
[75]
Kormann , A semi- Lagrangian Vlasov solver in tensor train format , SIAM Journal on Scientific Computing, 37 (2015), pp
K. Kormann , A semi- Lagrangian Vlasov solver in tensor train format , SIAM Journal on Scientific Computing, 37 (2015), pp. B613--B632
2015
-
[76]
Kressner and C
D. Kressner and C. Tobler , Algorithm 941: htucker---A MATLAB toolbox for tensors in hierarchical Tucker format , ACM Transactions on Mathematical Software, 40 (2014), pp. 1--22
2014
-
[77]
Nakao, G
J. Nakao, G. Ceruti, and L. Einkemmer , A low-rank, high-order implicit-explicit integrator for three-dimensional convection-diffusion equations , Computer Physics Communications, (2026)
2026
-
[78]
I. V. Oseledets , Tensor-train decomposition , SIAM Journal on Scientific Computing, 33 (2011), pp. 2295--2317
2011
-
[79]
Perez-Garcia, F
D. Perez-Garcia, F. Verstraete, M. M. Wolf, and J. I. Cirac , Matrix product state representations , Quantum Information & Computation, 7 (2007), pp. 401--430
2007
-
[80]
Rodgers and D
A. Rodgers and D. Venturi , Implicit integration of nonlinear evolution equations on tensor manifolds , Journal of Scientific Computing, 97 (2023), p. 33
2023
-
[81]
Saad , A flexible inner-outer preconditioned GMRES algorithm , SIAM Journal on Scientific Computing, 14 (1993), pp
Y. Saad , A flexible inner-outer preconditioned GMRES algorithm , SIAM Journal on Scientific Computing, 14 (1993), pp. 461--469
1993
-
[82]
W. A. Sands, W. Guo, J.-M. Qiu, and T. Xiong , High-order adaptive rank integrators for multi-scale linear kinetic transport equations in the hierarchical Tucker format , SIAM Journal on Scientific Computing, 47 (2025), pp. A3383--A3412
2025
-
[83]
Simoncini , Numerical solution of a class of third order tensor linear equations , Bollettino dell'Unione Matematica Italiana, 13 (2020), pp
V. Simoncini , Numerical solution of a class of third order tensor linear equations , Bollettino dell'Unione Matematica Italiana, 13 (2020), pp. 429--439
2020
-
[84]
Trottenberg, C
U. Trottenberg, C. W. Oosterlee, and A. Sch \"u ller , Multigrid , Academic Press, San Diego, CA, 2000
2000
-
[85]
L. R. Tucker , Some mathematical notes on three-mode factor analysis , Psychometrika, 31 (1966), pp. 279--311
1966
-
[86]
Wang and J
G. Wang and J. Hu , Dynamical Tensor Train approximation for kinetic equations , Journal of Computational Physics, (2026), p. 114884
2026
-
[87]
Ye and N
E. Ye and N. F. Loureiro , Quantized tensor networks for solving the Vlasov--Maxwell equations , Journal of Plasma Physics, 90 (2024), p. 805900301
2024
-
[88]
Ye and N
E. Ye and N. F. G. Loureiro , Quantum-inspired method for solving the Vlasov--Poisson equations , Physical Review E, 106 (2022), p. 035208
2022
-
[89]
Zheng, W
N. Zheng, W. A. Sands, D. Hayes, A. J. Christlieb, and J.-M. Qiu , A semi- Lagrangian adaptive rank ( SLAR ) method for high-dimensional Vlasov dynamics , 2025
2025
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