arXiv:2412.17281cs.LG2024-12中稿 · AAAI被引 4

从局部切片测量中恢复低管秩张量,突破全张量感知瓶颈。

Non-Convex Tensor Recovery from Local Measurements

  • 用两个紧凑因子重参数化张量,构建非凸优化模型。
  • 算法在 $\mathcal O(\kappa^2 \log \frac{1}{\varepsilon})$ 次迭代内实现 $\varepsilon$-精度恢复。
  • 适用于高条件数张量,尤其适合医疗影像等局部采样场景。

针对全张量感知不可行的场景,本文提出一种新型张量压缩感知模型,仅通过相互独立的矩阵对每个横向切片进行测量。利用低管秩结构,将未知张量 $\boldsymbol{\mathcal X}^\star$ 重参数化为两个紧凑张量因子,并将其恢复问题建模为非凸最小化问题。为此,我们首先提出交替最小化算法 extsf{Alt-PGD-Min},分别采用投影梯度下降与精确最小化步骤迭代优化两因子。尽管存在非凸性,我们证明 extsf{Alt-PGD-Min} 可在 $\mathcal O\left( \kappa^2 \log \frac{1}{\varepsilon}\right)$ 次迭代内达到 $\varepsilon$-精度恢复,样本复杂度为 $\mathcal O\left( \kappa^6 r n_3 \log n_3 \left( \kappa^2 r (n_1 + n_2) + n_1 \log \frac{1}{\varepsilon} \right) \right)$,其中 $\kappa$ 表示 $\boldsymbol{\mathcal X}^\star$ 的张量条件数。为进一步加速收敛,特别是当张量条件数 $\kappa$ 较大时,我们证明了 extsf{Alt-ScalePGD-Min} 算法,其使用可高效计算的近似海森矩阵预处理梯度更新。结果表明, extsf{Alt-ScalePGD-Min} 实现了与 $\kappa$ 无关的迭代复杂度 $\mathcal O(\log \frac{1}{\varepsilon})$,并将样本复杂度优化至 $\mathcal O\left( \kappa^4 r n_3 \log n_3 \left( \kappa^4 r (n_1 + n_2) + n_1 \log \frac{1}{\varepsilon} \right) \right)$。实验验证了所提方法的有效性。

原文摘要 · Abstract (English)

Motivated by the settings where sensing the entire tensor is infeasible, this paper proposes a novel tensor compressed sensing model, where measurements are only obtained from sensing each lateral slice via mutually independent matrices. Leveraging the low tubal rank structure, we reparameterize the unknown tensor ${\boldsymbol {\mathcal X}}^\star$ using two compact tensor factors and formulate the recovery problem as a nonconvex minimization problem. To solve the problem, we first propose an alternating minimization algorithm, termed \textsf{Alt-PGD-Min}, that iteratively optimizes the two factors using a projected gradient descent and an exact minimization step, respectively. Despite nonconvexity, we prove that \textsf{Alt-PGD-Min} achieves $ε$-accuracy recovery with $\mathcal O\left( κ^2 \log \frac{1}ε\right)$ iteration complexity and $\mathcal O\left( κ^6rn_3\log n_3 \left( κ^2r\left(n_1 + n_2 \right) + n_1 \log \frac{1}ε\right) \right)$ sample complexity, where $κ$ denotes tensor condition number of $\boldsymbol{\mathcal X}^\star$. To further accelerate the convergence, especially when the tensor is ill-conditioned with large $κ$, we prove \textsf{Alt-ScalePGD-Min} that preconditions the gradient update using an approximate Hessian that can be computed efficiently. We show that \textsf{Alt-ScalePGD-Min} achieves $κ$ independent iteration complexity $\mathcal O(\log \frac{1}ε)$ and improves the sample complexity to $\mathcal O\left( κ^4 rn_3 \log n_3 \left( κ^4r(n_1+n_2) + n_1 \log \frac{1}ε\right) \right)$. Experiments validate the effectiveness of the proposed methods.

张量恢复压缩感知非凸优化

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