Fast Tensor Completion via Approximate Richardson Iteration
Mehrdad GhadiriMatthew FahrbachYunbum KookAli Jadbabaie
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.
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.
- Paper: Tensor Decomposition for Signal Processing and Machine Learning, Nicholas D. Sidiropoulos et al. (2016). Provides the foundational algebraic formulations and alternating optimization algorithms for CP and Tucker tensor decompositions that the source paper's lifting and regression subroutines build upon.
- Paper: Tensor Completion for Estimating Missing Values in Visual Data, Ji Liu et al. (2009). Introduces the formulation and optimization foundations for recovering missing entries in visual data via tensor completion, establishing the core problem setting tackled in the source.
- Paper: Spectral Regularization Algorithms for Learning Large Incomplete Matrices, Rahul Mazumder et al. (2010). Presents foundational iterative regularized regression techniques for completing large-scale missing matrices, which serve as the direct mathematical predecessor to low-rank tensor completion solvers.
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