The Power of Preconditioning in Overparameterized Low-Rank Matrix
Sensing
- URL: http://arxiv.org/abs/2302.01186v3
- Date: Mon, 6 Nov 2023 13:47:12 GMT
- Title: The Power of Preconditioning in Overparameterized Low-Rank Matrix
Sensing
- Authors: Xingyu Xu, Yandi Shen, Yuejie Chi, Cong Ma
- Abstract summary: $textsfScaledGD($lambda$)$ is a preconditioned gradient descent method to tackle the low-rank matrix sensing problem.
We show that $textsfScaledGD($lambda$)$ converges to the true low-rank matrix at a constant linear rate after a small number of iterations.
- Score: 42.905196856926615
- License: http://creativecommons.org/licenses/by/4.0/
- Abstract: We propose $\textsf{ScaledGD($\lambda$)}$, a preconditioned gradient descent
method to tackle the low-rank matrix sensing problem when the true rank is
unknown, and when the matrix is possibly ill-conditioned. Using
overparametrized factor representations, $\textsf{ScaledGD($\lambda$)}$ starts
from a small random initialization, and proceeds by gradient descent with a
specific form of damped preconditioning to combat bad curvatures induced by
overparameterization and ill-conditioning. At the expense of light
computational overhead incurred by preconditioners,
$\textsf{ScaledGD($\lambda$)}$ is remarkably robust to ill-conditioning
compared to vanilla gradient descent ($\textsf{GD}$) even with
overprameterization. Specifically, we show that, under the Gaussian design,
$\textsf{ScaledGD($\lambda$)}$ converges to the true low-rank matrix at a
constant linear rate after a small number of iterations that scales only
logarithmically with respect to the condition number and the problem dimension.
This significantly improves over the convergence rate of vanilla $\textsf{GD}$
which suffers from a polynomial dependency on the condition number. Our work
provides evidence on the power of preconditioning in accelerating the
convergence without hurting generalization in overparameterized learning.
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