pith. sign in

arxiv: 2605.17089 · v1 · pith:BXPLTHTJnew · submitted 2026-05-16 · 🧮 math.OC

A preconditioned augmented Lagrangian method for solving semidefinite programming problems

Pith reviewed 2026-05-20 14:43 UTC · model grok-4.3

classification 🧮 math.OC
keywords semidefinite programmingaugmented Lagrangian methodpreconditioningtangent space projectionlow-rank solutionsconvex optimizationSDP solver
0
0 comments X

The pith

A weighted penalty preconditioner from tangent space projection accelerates the augmented Lagrangian method for ill-conditioned semidefinite programs.

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

This paper proposes a preconditioned augmented Lagrangian method for semidefinite programming. The preconditioner modifies the penalty term in the subproblems using a weight matrix from the tangent space projection of the feasible region. This modification leads to faster convergence particularly when the problems are ill-conditioned. Integrating the preconditioned method with the SDPF feasible approach creates the SDPF+ solver, which can manage convex SDPs including those with nonlinear objectives. Tests show SDPF+ often beats competing solvers on large problems with low-rank optimal solutions.

Core claim

The central discovery is that incorporating a weight matrix derived from the projection onto the tangent space of the feasible region into a weighted penalty function within the augmented Lagrangian subproblems substantially speeds up the solution process for ill-conditioned semidefinite programming problems. Combining this preconditioned ALM with the previously developed SDPF method results in the SDPF+ solver that efficiently addresses large-scale convex SDPs possibly featuring nonlinear objective functions.

What carries the argument

The weighted penalty function in the ALM subproblem, with its weight matrix coming from the tangent space projection operator onto the feasible region.

Load-bearing premise

The projection onto the tangent space produces a weight matrix that can be applied cheaply and stays numerically stable for the ill-conditioned SDPs that occur in applications.

What would settle it

Running the preconditioned ALM and the standard ALM on the same set of ill-conditioned SDP test problems and finding no consistent reduction in iteration counts or runtime would indicate the preconditioning does not accelerate convergence as claimed.

Figures

Figures reproduced from arXiv: 2605.17089 by Kim-Chuan Toh, Tianyun Tang.

Figure 1
Figure 1. Figure 1: Cholesky factor of MR for the Lov´asz Theta problem G51. PALM with exact Cholesky decomposition uses 28.4s, PALM with incomplete Cholesky decomposition uses 7.49s. to construct. In our numerical test for this instance, PALM equipped with incomplete Cholesky preconditioning is approximately three times faster than that with the exact Cholesky decomposition. In our implementation, the weight matrix in PALM i… view at source ↗
Figure 2
Figure 2. Figure 2: Rank evolution of SDPF+ for the rank-1 tensor appro [PITH_FULL_IMAGE:figures/full_fig_p018_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: Performance profile for the test results of 2RDM. [PITH_FULL_IMAGE:figures/full_fig_p019_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: Performance profile for test results on Hans Mittel [PITH_FULL_IMAGE:figures/full_fig_p019_4.png] view at source ↗
read the original abstract

In this work, we propose a preconditioned augmented Lagrangian method (ALM) for solving semidefinite programming (SDP) problems. The preconditioner is implemented via a weighted penalty function in the ALM subproblem, with the weight matrix derived from the projection operator onto the tangent space of the feasible region. This simple yet effective modification significantly accelerates ALM, particularly for ill-conditioned SDPs. By combining the preconditioned ALM with our previously developed feasible method SDPF, we develop SDPF+, an SDP solver capable of handling convex problems with possibly nonlinear objective functions. Extensive numerical experiments demonstrate the efficiency and robustness of SDPF+, showing that it can generally outperform other solvers on large-scale SDPs whose optimal solutions exhibit low-rank structure.

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

1 major / 2 minor

Summary. This paper proposes a preconditioned augmented Lagrangian method (ALM) for semidefinite programming (SDP) problems. The preconditioner is realized through a weighted penalty function in the ALM subproblem, with the weight matrix obtained from the projection operator onto the tangent space of the feasible region. The method is combined with the SDPF feasible method to create SDPF+, suitable for convex SDPs possibly with nonlinear objectives. The authors present extensive numerical experiments to illustrate the efficiency and robustness of SDPF+, particularly its ability to outperform other solvers on large-scale SDPs with low-rank optimal solutions.

Significance. If the performance claims hold under more detailed scrutiny, the work could meaningfully advance SDP solvers by accelerating ALM on ill-conditioned instances and delivering competitive results on large low-rank problems. The numerical results appear consistent with the claimed acceleration and outperformance on the tested instances, with the per-iteration overhead of the tangent-space projection remaining controlled in the low-rank regime; these constitute concrete strengths of the manuscript.

major comments (1)
  1. Numerical Experiments section: the description of the test-set construction, stopping criteria, and any statistical assessment of performance differences is insufficient. This information is load-bearing for the central claim that SDPF+ generally outperforms other solvers on large-scale low-rank SDPs.
minor comments (2)
  1. Abstract: the claim of 'extensive numerical experiments' would benefit from an explicit cross-reference to the relevant tables or figures.
  2. Preconditioner construction: the discussion of numerical stability of the derived weight matrix across ill-conditioned instances could be expanded with a brief remark on observed condition numbers or failure modes.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for the careful review and the positive assessment of the potential impact of our work on accelerating ALM for ill-conditioned SDPs. We address the single major comment below and will incorporate the suggested improvements in the revised manuscript.

read point-by-point responses
  1. Referee: Numerical Experiments section: the description of the test-set construction, stopping criteria, and any statistical assessment of performance differences is insufficient. This information is load-bearing for the central claim that SDPF+ generally outperforms other solvers on large-scale low-rank SDPs.

    Authors: We agree that additional detail in the Numerical Experiments section would strengthen the presentation and better support the central performance claims. In the revision we will expand the description of the test-set construction to clarify how the large-scale low-rank convex SDP instances were generated (including the specific random models and parameter ranges used), provide the precise stopping criteria and tolerances applied to SDPF+ as well as to the competing solvers, and include statistical summaries such as performance profiles or average runtime ratios across the instance collection. These additions will make the experimental evidence more transparent without altering the reported results. revision: yes

Circularity Check

0 steps flagged

No significant circularity detected

full rationale

The paper presents an algorithmic construction for a preconditioned ALM where the weight matrix is explicitly built from the tangent-space projection operator onto the feasible region. This modification is justified by reference to standard ALM convergence theory together with new numerical experiments on ill-conditioned instances. The subsequent combination with the authors' earlier SDPF method to produce SDPF+ is a straightforward composition that does not alter the independent status of the preconditioner derivation or the reported acceleration. No equation is shown to be equivalent by construction to a fitted parameter, no uniqueness theorem is imported from the authors' own prior work to forbid alternatives, and the performance claims rest on external experimental benchmarks rather than internal self-reference. The derivation chain therefore remains self-contained against the stated assumptions and observed results.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The paper relies on existing convergence theory for augmented Lagrangian methods and on the well-definedness of the tangent-space projection operator; no new free parameters, ad-hoc axioms, or invented entities are introduced in the abstract.

axioms (1)
  • standard math Standard convergence theory for augmented Lagrangian methods continues to apply after the introduction of the tangent-space-derived weighting.
    The preconditioner is presented as a modification that preserves the outer ALM framework.

pith-pipeline@v0.9.0 · 5644 in / 1275 out tokens · 55203 ms · 2026-05-20T14:43:33.298048+00:00 · methodology

discussion (0)

Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.

Reference graph

Works this paper leans on

53 extracted references · 53 canonical work pages

  1. [1]

    E. Abbe. Community detection and stochastic block model s: recent developments. Journal of Machine Learning Research , 18(177):1–86, 2018

  2. [2]

    Absil, R

    P.-A. Absil, R. Mahony, and R. Sepulchre. Optimization a lgorithms on matrix man- ifolds. In Optimization Algorithms on Matrix Manifolds . Princeton University Press, 2009

  3. [3]

    A. I. Barvinok. Problems of distance geometry and convex properties of quadratic maps. Discrete & Computational Geometry , 13(2):189–202, 1995

  4. [4]

    H. H. Bauschke, P. L. Combettes, H. H. Bauschke, and P. L. C ombettes. Correction to: convex analysis and monotone operator theory in Hilbert spaces. Springer, 2017

  5. [5]

    Beck and M

    A. Beck and M. Teboulle. A fast iterative shrinkage-thre sholding algorithm for linear inverse problems. SIAM J. on Imaging Sciences , 2(1):183–202, 2009

  6. [6]

    N. Boumal. An introduction to optimization on smooth manifolds . Cambridge Univer- sity Press, 2023

  7. [7]

    Bredies and H

    K. Bredies and H. Sun. A proximal point analysis of the pre conditioned alternating direction method of multipliers. Journal of Optimization Theory and Applications , 173:878–907, 2017

  8. [8]

    S. Burer. On the copositive representation of binary and continuous nonconvex quadratic programs. Mathematical Programming, 120(2):479–495, 2009. 23

  9. [9]

    Burer and C

    S. Burer and C. Choi. Computational enhancements in low- rank semidefinite program- ming. Optimisation Methods and Software , 21(3):493–512, 2006

  10. [10]

    Burer and R

    S. Burer and R. D. Monteiro. A nonlinear programming alg orithm for solving semidef- inite programs via low-rank factorization. Mathematical Programming, 95(2):329–357, 2003

  11. [11]

    R. E. Burkard, S. E. Karisch, and F. Rendl. QAPLIB–a quad ratic assignment problem library. Journal of Global optimization , 10:391–403, 1997

  12. [12]

    Y. Cui, D. Sun, and K.-C. Toh. On the r-superlinear conve rgence of the KKT residuals generated by the augmented Lagrangian method for convex com posite conic program- ming. Mathematical Programming, 178(1):381–415, 2019

  13. [13]

    Giselsson and S

    P. Giselsson and S. Boyd. Diagonal scaling in douglas-r achford splitting and admm. In 53rd IEEE Conference on Decision and Control , pages 5033–5039. IEEE, 2014

  14. [14]

    Graham, H

    N. Graham, H. Hu, J. Im, X. Li, and H. Wolkowicz. A restric ted dual peaceman- rachford splitting method for a strengthened dnn relaxatio n for qap. INFORMS Jour- nal on Computing , 34(4):2125–2143, 2022

  15. [15]

    Q. Han, C. Li, Z. Lin, C. Chen, Q. Deng, D. Ge, H. Liu, and Y. Ye. A low-rank ADMM splitting approach for semidefinite programming. INFORMS J. on Computing, to appear, 2025

  16. [16]

    D. Hou, T. Tang, and K.-C. Toh. A low-rank augmented Lagr angian method for doubly nonnegative relaxations of mixed-binary quadratic progra ms. Operations Resarch, to appear., 2025

  17. [17]

    D. Hou, T. Tang, and K.-C. Toh. Rinnal+: a riemannian alm solver for sdp-rlt relax- ations of mixed-binary quadratic programs: Di hou et al. Mathematical Programming Computation, pages 1–57, 2026

  18. [18]

    Jiang, D

    K. Jiang, D. Sun, and K.-C. Toh. An inexact accelerated p roximal gradient method for large scale linearly constrained convex SDP. SIAM J. on Optimization , 22(3):1042– 1064, 2012

  19. [19]

    Kontogiorgis and R

    S. Kontogiorgis and R. R. Meyer. A variable-penalty alt ernating directions method for convex optimization. Mathematical Programming, 83(1):29–53, 1998

  20. [20]

    J. B. Lasserre. Global optimization with polynomials a nd the problem of moments. SIAM J. on Optimization , 11(3):796–817, 2001

  21. [21]

    X. Li, D. Sun, and K.-C. Toh. QSDPNAL: a two-phase augmen ted Lagrangian method for convex quadratic semidefinite programming. Mathematical Programming Compu- tation, 10(4):703–743, 2018

  22. [22]

    Y. Liu, Y. Xu, and W. Yin. Acceleration of primal–dual me thods by preconditioning and simple subproblem procedures. Journal of Scientific Computing , 86(2):21, 2021. 24

  23. [23]

    Marteau-Ferey, F

    U. Marteau-Ferey, F. Bach, and A. Rudi. Non-parametric models for non-negative functions. Advances in Neural Information Processing Systems , 33:12816–12826, 2020

  24. [24]

    R. D. Monteiro, A. Sujanani, and D. Cifuentes. A low-ran k augmented Lagrangian method for large-scale semidefinite programming based on a h ybrid convex-nonconvex approach. arXiv preprint arXiv:2401.12490 , 2024

  25. [25]

    Nakata, B

    M. Nakata, B. J. Braams, K. Fujisawa, M. Fukuda, J. K. Per cus, M. Yamashita, and Z. Zhao. Variational calculation of second-order reduced d ensity matrices by strong n-representability conditions and an accurate semidefinit e programming solver. The Journal of Chemical Physics , 128(16), 2008

  26. [26]

    Nakata, H

    M. Nakata, H. Nakatsuji, M. Ehara, M. Fukuda, K. Nakata, and K. Fujisawa. Vari- ational calculations of fermion second-order reduced dens ity matrices by semidefinite programming algorithm. The Journal of Chemical Physics , 114(19):8282–8292, 2001

  27. [27]

    Nie and L

    J. Nie and L. Wang. Semidefinite relaxations for best ran k-1 tensor approximations. SIAM J. on Matrix Analysis and Applications , 35(3):1155–1179, 2014

  28. [28]

    Nocedal and S

    J. Nocedal and S. J. Wright. Numerical Optimization. Springer, 1999

  29. [29]

    G. Pataki. On the rank of extreme matrices in semidefinit e programs and the mul- tiplicity of optimal eigenvalues. Mathematics of Operations Research , 23(2):339–358, 1998

  30. [30]

    Pock and A

    T. Pock and A. Chambolle. Diagonal preconditioning for first order primal-dual algo- rithms in convex optimization. In 2011 International Conference on Computer Vision , pages 1762–1769, 2011

  31. [31]

    Povh and F

    J. Povh and F. Rendl. Copositive and semidefinite relaxa tions of the quadratic assign- ment problem. Discrete Optimization, 6(3):231–241, 2009

  32. [32]

    Qi and D

    H. Qi and D. Sun. An augmented Lagrangian dual approach f or the H-weighted nearest correlation matrix problem. IMA J. of Numerical Analysis , 31(2):491–511, 2011

  33. [33]

    F. Rendl. Semidefinite programming and combinatorial o ptimization. Applied Numer- ical Mathematics, 29(3):255–281, 1999

  34. [34]

    R. T. Rockafellar. Augmented Lagrangians and applicat ions of the proximal point algorithm in convex programming. Mathematics of Operations Research , 1(2):97–116, 1976

  35. [35]

    N. J. A. Sloane. Challenge problems: Independent sets i n graphs. http://www. research. att. com/˜ njas/doc/graphs. html , 2005

  36. [36]

    R. Sotirov. An efficient semidefinite programming relaxa tion for the graph partition problem. INFORMS Journal on Computing , 26(1):16–30, 2014

  37. [37]

    Sun, K.-C

    D. Sun, K.-C. Toh, Y. Yuan, and X.-Y. Zhao. SDPNAL+: A Mat lab software for semidefinite programming with bound constraints (version 1 .0). Optimization Methods and Software, 35(1):87–115, 2020. 25

  38. [38]

    D. Sun, Y. Yuan, G. Zhang, and X. Zhao. Accelerating prec onditioned ADMM via degenerate proximal point mappings. SIAM J. on Optimization , 35(2):1165–1193, 2025

  39. [39]

    Tang and K.-C

    T. Tang and K.-C. Toh. Exploring chordal sparsity in sem idefinite programming with sparse plus low-rank data matrices. arXiv preprint arXiv:2410.23849 , 2024

  40. [40]

    Tang and K.-C

    T. Tang and K.-C. Toh. A feasible method for general conv ex low-rank SDP problems. SIAM J. on Optimization , 34(3):2169–2200, 2024

  41. [41]

    Tang and K.-C

    T. Tang and K.-C. Toh. Solving graph equipartition SDPs on an algebraic variety. Mathematical Programming, 204(1):299–347, 2024

  42. [42]

    K.-C. Toh, M. J. Todd, and R. H. T¨ ut¨ unc¨ u. SDPT3—a Matl ab software package for semidefinite programming, version 1.3. Optimization Methods and Software , 11(1- 4):545–581, 1999

  43. [43]

    Wang and L

    J. Wang and L. Hu. Solving low-rank semidefinite program s via manifold optimization. Journal of Scientific Computing , 104(1):1–33, 2025

  44. [44]

    Wang and C

    S. Wang and C. Ding. Local convergence analysis of augme nted Lagrangian method for nonlinear semidefinite programming. Computational Optimization and Applications , 87(1):39–81, 2024

  45. [45]

    Y. Xu. Iteration complexity of inexact augmented Lagra ngian methods for constrained convex programming. Mathematical Programming, 185(1):199–244, 2021

  46. [46]

    L. Yang, D. Sun, and K.-C. Toh. SDPNAL+: a majorized semi smooth Newton- CG augmented Lagrangian method for semidefinite programmin g with nonnegative constraints. Mathematical Programming Computation, 7(3):331–366, 2015

  47. [47]

    X.-Y. Zhao, D. Sun, and K.-C. Toh. A Newton-CG augmented Lagrangian method for semidefinite programming. SIAM J. Optimization , 20(4):1737–1765, 2010. 26 A Proof of Theorem 1 In the following analysis, we always assume k≥ 2. From (19) and (20), we have that ∂zg(zk)−H ∗ (γ k) = ( ∂X δSn + (X k) +∇ f (X k)−A ∗ (λ k)−B ∗(µ k), ∂ yδP (yk) + µ k ) . (41) Becaus...

  48. [48]

    blk is a K× 2 cell array that specifies the block structure of the variables, wh ere K is the number of blocks. For each k∈ [K], blk{k,1} is a character indicating the type of the k-th block, which can be one of the following: • ’s’: symmetric positive semidefinite matrix variable, 28 • ’l’: nonnegative vector variable, • ’f’: free vector variable. blk{k,2}...

  49. [49]

    It has two columns when the user wants to make use of the sparse plus low- rank structure of the constraint matrices Ai’s described in [39]

    At is a K× 1 or K× 2 cell array that describe the linear operator A in (SDPG1). It has two columns when the user wants to make use of the sparse plus low- rank structure of the constraint matrices Ai’s described in [39]. Suppose the k-th block is a matrix variable with dimension n and the constraint matrices {Ai}i∈ [m] have sparse plus low-rank decomposit...

  50. [50]

    C is either a cell array or a function handle that describes the object ive function f in (SDPG1). When the SDP problem has linear objective function f (X) = ∑K i=1 ⟨ Ci, X i ⟩ such that the matrix blocks have sparse plus low-rank decomposition Ci = Cs i + Uidiag(di)U ⊤ i , we have that C{i, 1} = { Ci if blk{i,1}̸ = ’s’ Cs i if blk{i,1} = ’s’. (58) C{i, 2...

  51. [51]

    b is an m-dimensional vector which is exactly the vector b in (SDPG1)

  52. [52]

    The data structure of Bt is the same as At

    Bt,l,u are used to denote the inequality constraint, l≤B (X)≤ u, in (SDPG1). The data structure of Bt is the same as At

  53. [53]

    The user can refer to the main function sdpfplus.m for the complete list of available parameters

    par is a struct-type array that contains the parameters and options for the so lver. The user can refer to the main function sdpfplus.m for the complete list of available parameters. Although there are many parameters, most of them are intended f or solver development and have been pre-tuned. Here, we highlight only a few important param eters that are co...