Fast Tensor Completion via Approximate Richardson Iteration

Mehrdad GhadiriMatthew FahrbachYunbum KookAli Jadbabaie

article2025ICML0 citations

Develops an approximate Richardson iteration framework that enables fast tensor decomposition solvers to tackle tensor completion in sublinear time, achieving up to 100x speedups over direct methods on real-world datasets.

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Large-scale multidimensional data across healthcare imaging, signal processing, and machine learning frequently suffers from missing observations. Reconstructing this missing information, a task known as tensor completion, is computationally intensive. While traditional tensor decomposition methods exploit rich algebraic symmetries to process fully observed datasets rapidly, these structural efficiencies are lost when dealing with partially observed data. As a result, standard completion algorithms rely on direct matrix computations that scale poorly with data size and become severe computational bottlenecks.

The article demonstrates a novel lifting framework that restores the lost algebraic structure in tensor completion subproblems, enabling fast and scalable completion via approximate randomized subroutines. The authors establish theoretical convergence guarantees for this approach and evaluate its practical performance against standard methods.

The authors approach the challenge by reformulating the unstructured completion problem into a higher-dimensional space where missing values act as free variables. This formulation is solved using an iterative alternating minimization technique that theoretically mirrors a preconditioned Richardson iteration. By proving that internal regression steps can be solved approximately without sacrificing overall convergence, the authors incorporate state-of-the-art leverage-score row sampling techniques for major decomposition models, including CP, Tucker, and tensor-train formats. The methodology was validated through mathematical proofs as well as empirical experiments on synthetic benchmarks and real-world cardiac MRI and hyperspectral imaging datasets.

The investigation produced several key findings. First, lifting the masked regression problem into a higher-dimensional form provably preserves the exact optimal solution while completely restoring the Kronecker and Khatri-Rao algebraic structures. Second, the proposed approximate iterative algorithm converges at the same rate as the standard Richardson iteration, provided the approximation error per step remains within a specified bound. Third, empirical tests on real-world datasets demonstrated that the method achieved comparable reconstruction accuracy to direct methods while running up to 100 times faster. Fourth, introducing an accelerated variant with adaptive step sizes further reduced iteration counts and total runtimes, particularly in settings with very low observation rates.

These results demonstrate that organizations processing massive, incomplete multidimensional datasets can drastically cut computational runtime and hardware costs without degrading data recovery accuracy. Because the framework operates modularly with existing decomposition subroutines, practitioners can directly benefit from future advancements in randomized linear algebra and tensor sketching algorithms.

Engineering and data science teams dealing with heavy tensor completion workloads should consider adopting lifted, sampling-based alternating least squares frameworks over direct matrix inversion approaches. For further development, researchers should conduct formal theoretical analyses on the convergence acceleration provided by adaptive step-size extrapolation and explore integrations across broader tensor network architectures.

Confidence in these findings is reinforced by rigorous theoretical proofs and consistent empirical performance across diverse datasets. However, practitioners should note that the algorithm's convergence speed depends on data incoherence and the fraction of observed entries, meaning highly sparse tensors may require more iterations to reach target accuracy.

No sufficiently relevant recommendations were found.

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Abstract

We study tensor completion (TC) through the lens of low-rank tensor decomposition (TD). Many TD algorithms use fast alternating minimization methods to solve highly structured linear regression problems at each step (e.g., for CP, Tucker, and tensor-train decompositions). However, such algebraic structure is often lost in TC regression problems, making direct extensions unclear. This work proposes a novel lifting method for approximately solving TC regression problems using structured TD regression algorithms as blackbox subroutines, enabling sublinear-time methods. We analyze the convergence rate of our approximate Richardson iteration-based algorithm, and our empirical study shows that it can be 100x faster than direct methods for CP completion on real-world tensors.

Table of Contents

  • 1 Introduction
  • 1.1 Our Contributions
  • 1.2 Related Work
  • 2 Preliminaries
  • 2.1 Tensor Decompositions
  • 2.2 ALS Formulations
  • 3 Approximate Richardson Iteration
  • 3.1 Lifting to a Structured Problem
  • 3.2 Iterative Methods for the Lifted Problem
  • 3.3 Approximately Solving the Lifted Problem
  • 4 Sampling Methods for Tensor Completion
  • 4.1 CP Completion
  • 4.2 Tucker Completion
  • 4.2.1 Core tensor update
  • 4.2.2 Factor matrix update
  • 4.3 TT Completion
  • 5 Experiments
  • 5.1 Warm-Up: Coupled Matrix Problem
  • 5.2 CP Completion
  • 6 Conclusion
  • References
  • A Missing Details for
  • A.1 Least-Squares Linear Regression
  • A.2 Leverage Score Sampling for Tensor Decomposition
  • A.3 Tensor-Train Decomposition
  • A.4 Tensor Networks
  • B Missing Analysis for
  • B.1 Proof of
  • B.2 Proof of
  • B.3 Proof of
  • B.4 Proof of
  • C Additional Details for
  • D Additional Details for
  • D.1 CP Completion
  • D.1.1 Synthetic Tensors
  • D.1.2 Accelerated Methods

Knowls

  1. Knowl 1 — Lifted Formulation of Masked Linear Regression for Tensor Completion

    model/method

    In tensor completion (TC), alternating least squares (ALS) requires solving linear regression problems over a subset of observed entries Ω⊆[I]\Omega \subseteq [I], where I=∏n=1NInI = \prod_{n=1}^N I_n is the total number of entries in an NN-th order tensor X∈RI1×⋯×IN\mathcal{X} \in \mathbb{R}^{I_1 \times \dots \times I_N}. Given a full structured design matrix A∈RI×RA \in \mathbb{R}^{I \times R} (such as a Kronecker or Khatri–Rao product) and an observation vector q∈R∣Ω∣q \in \mathbb{R}^{|\Omega|}, the subproblem is:

    x∗=arg⁡min⁡x∈RR∥AΩx−q∥22x^* = \arg\min_{x \in \mathbb{R}^R} \|A_\Omega x - q\|_2^2

    where AΩ∈R∣Ω∣×RA_\Omega \in \mathbb{R}^{|\Omega| \times R} contains the rows of AA indexed by Ω\Omega. Because AΩA_\Omega loses the algebraic product structure of AA, direct fast decomposition methods cannot be directly applied.

    The lifted formulation introduces free variables bΩˉ∈RI−∣Ω∣b_{\bar{\Omega}} \in \mathbb{R}^{I - |\Omega|} corresponding to the unobserved entries Ωˉ=[I]∖Ω\bar{\Omega} = [I] \setminus \Omega, setting the full lifted response vector to b=[bΩ; bΩˉ]∈RIb = [b_\Omega;\, b_{\bar{\Omega}}] \in \mathbb{R}^I with bΩ=qb_\Omega = q. The lifted problem is:

    (x∗,bΩˉ∗)=arg⁡min⁡x∈RR, bΩˉ∈RI−∣Ω∣∥Ax−b∥22(x^*, b_{\bar{\Omega}}^*) = \arg\min_{x \in \mathbb{R}^R, \, b_{\bar{\Omega}} \in \mathbb{R}^{I - |\Omega|}} \|Ax - b\|_2^2

    This is a convex quadratic program whose optimal parameter vector x∗x^* is identical to the solution of the original masked regression problem. Alternating between optimizing xx and updating bΩˉb_{\bar{\Omega}} restores access to the structured matrix AA in each regression step.

  2. Knowl 2 — Equivalence of Lifted Alternating Minimization and Preconditioned Richardson Iteration

    theoretical result

    Let A,P~∈RI×RA, \tilde{P} \in \mathbb{R}^{I \times R} and q~∈RI\tilde{q} \in \mathbb{R}^I such that P~−A\tilde{P} - A and [P~q~][\tilde{P} \quad \tilde{q}] are orthogonal, i.e., (P~−A)⊤[P~q~]=0(\tilde{P} - A)^\top [\tilde{P} \quad \tilde{q}] = 0. In the tensor completion setting, P~\tilde{P} and q~\tilde{q} correspond to the zero-masked matrix and vector where rows/entries outside the observed set Ω\Omega are set to 0, while AA is the full structured design matrix.

    The alternating minimization scheme (termed mini-ALS):

    q~(k)=q~+(A−P~)x(k)\tilde{q}^{(k)} = \tilde{q} + (A - \tilde{P}) x^{(k)}

    x(k+1)=arg⁡min⁡x∈RR∥Ax−q~(k)∥22x^{(k+1)} = \arg\min_{x \in \mathbb{R}^R} \|Ax - \tilde{q}^{(k)}\|_2^2

    simulates the preconditioned Richardson iteration with preconditioner matrix M=A⊤AM = A^\top A for the regression problem min⁡x∥P~x−q~∥22\min_{x} \|\tilde{P}x - \tilde{q}\|_2^2, yielding the update:

    x(k+1)=x(k)−(A⊤A)−1(P~⊤P~x(k)−P~⊤q~)x^{(k+1)} = x^{(k)} - (A^\top A)^{-1} (\tilde{P}^\top \tilde{P} x^{(k)} - \tilde{P}^\top \tilde{q})

  3. Knowl 3 — Approximate Mini-ALS Algorithm

    algorithm

    The approx-mini-als algorithm computes an approximate solution to the masked regression problem min⁡x∥P~x−q~∥22\min_x \|\tilde{P}x - \tilde{q}\|_2^2 by iteratively solving structured regression subproblems with an approximate solver.

    Input: Design matrix A∈RI×RA \in \mathbb{R}^{I \times R}, zero-masked matrix P~∈RI×R\tilde{P} \in \mathbb{R}^{I \times R}, zero-masked response q~∈RI\tilde{q} \in \mathbb{R}^I, spectral condition parameter β≥1\beta \ge 1 such that P~⊤P~⪯A⊤A⪯βP~⊤P~\tilde{P}^\top \tilde{P} \preceq A^\top A \preceq \beta \tilde{P}^\top \tilde{P}, target accuracy ε∈(0,1)\varepsilon \in (0, 1), per-step solver error tolerance ε^∈[0,1/β2)\hat{\varepsilon} \in [0, 1/\beta^2)
    Output: Approximate solution vector x~∈RR\tilde{x} \in \mathbb{R}^R
    Initialize x(0)=0x^{(0)} = 0
    K=⌈log⁡(2β/ε)2(1/β−ε^)⌉K = \left\lceil \frac{\log(2\beta / \varepsilon)}{2(1/\beta - \sqrt{\hat{\varepsilon}})} \right\rceil
    for k=0,1,…,K−1k = 0, 1, \dots, K-1 do
        Set q~(k)←q~+(A−P~)x(k)\tilde{q}^{(k)} \leftarrow \tilde{q} + (A - \tilde{P}) x^{(k)}
        Compute x(k+1)x^{(k+1)} using an approximate least-squares subroutine such that:
            ∥Ax(k+1)−q~(k)∥22≤(1+ε^)min⁡x∥Ax−q~(k)∥22\|A x^{(k+1)} - \tilde{q}^{(k)}\|_2^2 \le (1 + \hat{\varepsilon}) \min_x \|Ax - \tilde{q}^{(k)}\|_2^2
    return x(K)x^{(K)}

    The update q~(k)\tilde{q}^{(k)} is computed lazily, evaluating only the entries required by row sampling in the approximate least-squares solver.

  4. Knowl 4 — Convergence Rate and Error Bounds for Approximate Mini-ALS

    theoretical result

    Let A,P~∈RI×RA, \tilde{P} \in \mathbb{R}^{I \times R}, q~∈RI\tilde{q} \in \mathbb{R}^I, and β≥1\beta \ge 1 satisfy (P~−A)⊤[P~q~]=0(\tilde{P} - A)^\top [\tilde{P} \quad \tilde{q}] = 0 and P~⊤P~⪯A⊤A⪯βP~⊤P~\tilde{P}^\top \tilde{P} \preceq A^\top A \preceq \beta \tilde{P}^\top \tilde{P}.

    Let ε∈(0,1)\varepsilon \in (0, 1), ε^∈[0,1/β2)\hat{\varepsilon} \in [0, 1/\beta^2), and let approx-least-squares be an algorithm that for any x^∈RR\hat{x} \in \mathbb{R}^R and f=q~+(A−P~)x^f = \tilde{q} + (A - \tilde{P})\hat{x} computes an approximate solution x∈RRx \in \mathbb{R}^R in time O(T)O(T) satisfying:

    ∥Ax−f∥22≤(1+ε^)min⁡x∥Ax−f∥22\|Ax - f\|_2^2 \le (1 + \hat{\varepsilon}) \min_{x} \|Ax - f\|_2^2

    Then approx-mini-als running for k=⌈log⁡(2β/ε)2(1/β−ε^)⌉k = \left\lceil \frac{\log(2\beta/\varepsilon)}{2(1/\beta - \sqrt{\hat{\varepsilon}})} \right\rceil iterations outputs an approximate solution x~∈RR\tilde{x} \in \mathbb{R}^R in total time O(β1−ε^β⋅Tlog⁡(β/ε))O\left(\frac{\beta}{1 - \sqrt{\hat{\varepsilon}}\beta} \cdot T \log(\beta / \varepsilon)\right) such that:

    ∥P~x~−q~∥22≤(1+2ε^(1/β−ε^)2)min⁡x∥P~x−q~∥22+ε∥P~(P~⊤P~)−1P~⊤q~∥22\|\tilde{P}\tilde{x} - \tilde{q}\|_2^2 \le \left(1 + \frac{2\hat{\varepsilon}}{(1/\beta - \sqrt{\hat{\varepsilon}})^2}\right) \min_x \|\tilde{P}x - \tilde{q}\|_2^2 + \varepsilon \|\tilde{P}(\tilde{P}^\top \tilde{P})^{-1} \tilde{P}^\top \tilde{q}\|_2^2

  5. Knowl 5 — Accelerated Mini-ALS via Geometric Series Trajectory Extrapolation

    algorithm

    Accelerated Mini-ALS reduces the number of iterations required to solve the lifted quadratic program by extrapolating along the trajectory of consecutive iterates using geometric step sizing.

    Input: Full design matrix A∈RI×RA \in \mathbb{R}^{I \times R}, zero-masked matrix P~∈RI×R\tilde{P} \in \mathbb{R}^{I \times R}, zero-masked response q~∈RI\tilde{q} \in \mathbb{R}^I, number of iterations KK
    Output: Extrapolated iterate x(K)∈RRx^{(K)} \in \mathbb{R}^R
    Initialize x(0)=0x^{(0)} = 0
    for k=0,1,…,K−1k = 0, 1, \dots, K-1 do
        Set q~(k)←q~+(A−P~)x(k)\tilde{q}^{(k)} \leftarrow \tilde{q} + (A - \tilde{P}) x^{(k)}
        Compute standard mini-ALS update x^(k+1)←arg⁡min⁡x∥Ax−q~(k)∥22\hat{x}^{(k+1)} \leftarrow \arg\min_x \|Ax - \tilde{q}^{(k)}\|_2^2
        if kk is even (iteration index k+1k+1 is odd) then
            x(k+1)←x^(k+1)x^{(k+1)} \leftarrow \hat{x}^{(k+1)}
        else
            α←∥x^(k+1)−x(k)∥2∥x(k)−x(k−1)∥2\alpha \leftarrow \frac{\|\hat{x}^{(k+1)} - x^{(k)}\|_2}{\|x^{(k)} - x^{(k-1)}\|_2}
            x(k+1)←x(k)+11−α(x^(k+1)−x(k))x^{(k+1)} \leftarrow x^{(k)} + \frac{1}{1 - \alpha} (\hat{x}^{(k+1)} - x^{(k)})
    return x(K)x^{(K)}

    The extrapolation weight 11−α\frac{1}{1-\alpha} derives from summing the infinite geometric series of step vectors ∑j=0∞αj(x^(k+1)−x(k))\sum_{j=0}^\infty \alpha^j (\hat{x}^{(k+1)} - x^{(k)}) formed by coordinate descent steps on quadratic level sets. Setting α=0\alpha = 0 recovers standard mini-ALS.

  6. Knowl 6 — Spectral Condition Bound from Incoherence and Regularization

    theoretical result

    The spectral approximation parameter β\beta measures the condition number between the structured full design A⊤AA^\top A and the masked design P⊤P=AΩ⊤AΩP^\top P = A_\Omega^\top A_\Omega.

    Let rank(A)=s≤min⁡{I,R}\text{rank}(A) = s \le \min\{I, R\} and A=UΣV⊤A = U \Sigma V^\top be its compressed singular value decomposition. AA satisfies the standard incoherence condition with parameter μ\mu if:

    max⁡i∈[I]∥ei⊤U∥22≤μsI,max⁡r∈[R]∥V⊤er∥22≤μsR\max_{i \in [I]} \|e_i^\top U\|_2^2 \le \frac{\mu s}{I}, \quad \max_{r \in [R]} \|V^\top e_r\|_2^2 \le \frac{\mu s}{R}

    If each row of AA is observed independently with probability p≥cμslog⁡sIp \ge \frac{c \mu s \log s}{I} for an absolute constant cc, then with high probability:

    12A⊤A⪯1pAΩ⊤AΩ⪯32A⊤A\frac{1}{2} A^\top A \preceq \frac{1}{p} A_\Omega^\top A_\Omega \preceq \frac{3}{2} A^\top A

    which yields β=2/p\beta = 2/p.

    For arbitrary observation patterns, introducing an ℓ2\ell_2-regularization (ridge regression) parameter α=clog⁡sp\alpha = \frac{c \log s}{p} bounding the ridge leverage scores ai⊤(A⊤A+αζ2IR)−1ai≤1/αa_i^\top (A^\top A + \alpha \zeta^2 I_R)^{-1} a_i \le 1/\alpha (where ζ=max⁡i∥ai∥2\zeta = \max_i \|a_i\|_2) enforces the same spectral bound β=O(1/p)\beta = O(1/p).

  7. Knowl 7 — Sublinear-Time CP Tensor Completion via Khatri–Rao Leverage Score Sampling

    theoretical result

    For an NN-th order tensor X∈RI1×⋯×IN\mathcal{X} \in \mathbb{R}^{I_1 \times \dots \times I_N} with observed entries Ω\Omega, rank-RR CP completion updates factor matrices A(k)∈RIk×RA^{(k)} \in \mathbb{R}^{I_k \times R} by solving linear regression problems where the design matrix is the Khatri–Rao product A≠k=⨀n=1,n≠kNA(n)∈RI≠k×RA_{\ne k} = \bigodot_{n=1, n \ne k}^N A^{(n)} \in \mathbb{R}^{I_{\ne k} \times R} masked to Ω\Omega.

    By embedding the binary tree leverage score sampling data structure for Khatri–Rao products (Bharadwaj et al., 2023) as the approximate regression solver in approx-mini-als, one round of ALS (updating all NN factor matrices) runs in total time:

    O~(β2ε1∑n=1N(InR2+NR3)log⁡(1ε2))\tilde{O}\left( \frac{\beta^2}{\varepsilon_1} \sum_{n=1}^N (I_n R^2 + N R^3) \log\left(\frac{1}{\varepsilon_2}\right) \right)

    where β\beta is the spectral condition number between (A≠k)Ω⊤(A≠k)Ω(A_{\ne k})_\Omega^\top (A_{\ne k})_\Omega and A≠k⊤A≠kA_{\ne k}^\top A_{\ne k}, and ε1,ε2\varepsilon_1, \varepsilon_2 govern the relative error. The per-round running time is sublinear in the full tensor dimension I=∏n=1NInI = \prod_{n=1}^N I_n and has no explicit dependence on the number of observed entries ∣Ω∣|\Omega|.

  8. Knowl 8 — Sublinear-Time Tucker Tensor Completion via Kronecker Leverage Score Sampling

    theoretical result

    For an NN-th order tensor completion task with multilinear rank (R1,…,RN)(R_1, \dots, R_N), I=∏n=1NInI = \prod_{n=1}^N I_n, and R=∏n=1NRnR = \prod_{n=1}^N R_n, combining approx-mini-als with randomized Kronecker regression sketching (Fahrbach et al., 2022) yields the following running times per update:

    1. Core Tensor Update: The core tensor G∈RR1×⋯×RN\mathcal{G} \in \mathbb{R}^{R_1 \times \dots \times R_N} update with design matrix ⨂n=1NA(n)\bigotimes_{n=1}^N A^{(n)} runs in time:

    O~((∑n=1N(InRn+β4RnωN2ε12)+β2R2−θ∗ε1)βlog⁡(1ε2))\tilde{O}\left( \left( \sum_{n=1}^N \left(I_n R_n + \frac{\beta^4 R_n^\omega N^2}{\varepsilon_1^2}\right) + \frac{\beta^2 R^{2 - \theta^*}}{\varepsilon_1} \right) \beta \log\left(\frac{1}{\varepsilon_2}\right) \right)

    where ω\omega is the matrix multiplication exponent and θ∗>0\theta^* > 0 is a constant depending on {Rn}n=1N\{R_n\}_{n=1}^N.

    1. Factor Matrix Update: The factor matrix A(k)∈RIk×RkA^{(k)} \in \mathbb{R}^{I_k \times R_k} update runs in time:

    O~((∑n=1N(InRn+β4RnωN2ε12)+β2IkR≠k2−θ∗ε1+IkR∑n=1NRn)βlog⁡(1ε2))\tilde{O}\left( \left( \sum_{n=1}^N \left(I_n R_n + \frac{\beta^4 R_n^\omega N^2}{\varepsilon_1^2}\right) + \frac{\beta^2 I_k R_{\ne k}^{2 - \theta^*}}{\varepsilon_1} + I_k R \sum_{n=1}^N R_n \right) \beta \log\left(\frac{1}{\varepsilon_2}\right) \right)

    where R≠k=R/RkR_{\ne k} = R / R_k.

  9. Knowl 9 — Sublinear-Time Tensor-Train Completion via TT-Core Leverage Score Sampling

    theoretical result

    For an NN-th order tensor X∈RI1×⋯×IN\mathcal{X} \in \mathbb{R}^{I_1 \times \dots \times I_N} with observed entries Ω\Omega and uniform TT-rank Rn=RR_n = R for all n∈[N−1]n \in [N-1], each ALS step optimizes core tensor A(k)∈RR×Ik×RA^{(k)} \in \mathbb{R}^{R \times I_k \times R} against the Kronecker-type design matrix A≠k=A<k⊗A>k⊤∈RI≠k×R2A_{\ne k} = A_{<k} \otimes A_{>k}^\top \in \mathbb{R}^{I_{\ne k} \times R^2}.

    Using QR canonicalization to ensure (A≠k)⊤A≠k=IR2(A_{\ne k})^\top A_{\ne k} = I_{R^2} and sampling rows according to leverage scores decomposed across left and right TT chains (Bharadwaj et al., 2024), approx-mini-als executes one full round of NN TT-core updates in total time:

    O~(β2R4ε1∑n=1N(N+In)log⁡(1ε2))\tilde{O}\left( \frac{\beta^2 R^4}{\varepsilon_1} \sum_{n=1}^N (N + I_n) \log\left(\frac{1}{\varepsilon_2}\right) \right)

    where each updated core slice satisfies relative-error projection bounds with parameters ε1,ε2\varepsilon_1, \varepsilon_2.

  10. Knowl 10 — Empirical Convergence and Speedup of Mini-ALS and Accelerated Mini-ALS

    empirical result

    The empirical performance of mini-ALS, approximate-mini-ALS, and accelerated-mini-ALS was evaluated against direct ALS (which solves the normal equations via explicit inversion of (AΩ⊤AΩ)(A_\Omega^\top A_\Omega) in O(∣Ω∣R2+R3)O(|\Omega|R^2 + R^3) time) and PARAFAC-EM (Tomasi & Bro, 2005, which executes a single mini-ALS step per ALS round):

    1. Speedup on Real-World Tensors: On CARDIAC-MRI (256×256×14×20256 \times 256 \times 14 \times 20) and HYPERSPECTRAL (1024×1344×331024 \times 1344 \times 33) with sampling ratio p=0.1p = 0.1 and rank R=16R = 16, mini-ALS and accelerated-mini-ALS achieve up to 100x speedups over direct ALS while matching its relative reconstruction error ∥(X^−X)Ω∥F/∥XΩ∥F\|(\hat{\mathcal{X}} - \mathcal{X})_\Omega\|_F / \|\mathcal{X}_\Omega\|_F as tolerance ε→0\varepsilon \to 0.

    2. Scaling with Sample Ratio: As the observation fraction pp increases, the total runtime of direct ALS scales linearly with ∣Ω∣|\Omega|, whereas the runtime of mini-ALS decreases for ε<0.1\varepsilon < 0.1. This occurs because the lifted matrix A⊤AA^\top A becomes a better preconditioner for AΩ⊤AΩA_\Omega^\top A_\Omega (i.e., β→1\beta \to 1 as p→1p \to 1), reducing the number of inner Richardson iterations.

    3. Acceleration Advantage: Accelerated-mini-ALS consistently reaches lower relative error in fewer iterations than standard mini-ALS, with the largest runtime reductions occurring when pp is small (large β\beta).

    4. Coupled Matrix Problem: On AXB⊤+CYD⊤=EAXB^\top + CYD^\top = E (n=2000,d=10n=2000, d=10, 50% revealed entries), approximate-mini-ALS with 1% leverage score row sampling achieves lower mean squared error than direct ALS by exploring alternative optimization paths.

Coverage note — None was omitted; all primary theoretical results, algorithms, model formulations, and empirical findings have been extracted.

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Citation

MLA
Ghadiri, M., et al. “Fast Tensor Completion via Approximate Richardson Iteration”. Proceedings of the 42nd International Conference on Machine Learning (ICML 2025), 2025, http://arxiv.org/abs/2502.09534v2.
APA
Ghadiri, M., Fahrbach, M., Kook, Y., & Jadbabaie, A. (2025). Fast Tensor Completion via Approximate Richardson Iteration. Proceedings of the 42nd International Conference on Machine Learning (ICML 2025). http://arxiv.org/abs/2502.09534v2
Chicago
Ghadiri, M., M. Fahrbach, Y. Kook, and A. Jadbabaie. 2025. “Fast Tensor Completion via Approximate Richardson Iteration”. Proceedings of the 42nd International Conference on Machine Learning (ICML 2025). http://arxiv.org/abs/2502.09534v2.
Harvard
Ghadiri, M. et al. (2025) “Fast Tensor Completion via Approximate Richardson Iteration”, Proceedings of the 42nd International Conference on Machine Learning (ICML 2025) [Preprint]. Available at: http://arxiv.org/abs/2502.09534v2.
Vancouver
1. Ghadiri M, Fahrbach M, Kook Y, Jadbabaie A (2025) Fast Tensor Completion via Approximate Richardson Iteration. Proceedings of the 42nd International Conference on Machine Learning (ICML 2025)

BibTeX

@article{ghadiri2025fast,
  title = {Fast Tensor Completion via Approximate Richardson Iteration},
  author = {Ghadiri, Mehrdad and Fahrbach, Matthew and Kook, Yunbum and Jadbabaie, Ali},
  year = {2025},
  journal = {Proceedings of the 42nd International Conference on Machine Learning (ICML 2025)},
  url = {http://arxiv.org/abs/2502.09534v2},
  eprint = {2502.09534}
}
Metadata:arXiv

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