arXiv:2409.01570stat.MLcs.LG2024-09被引 3

提出平滑损失函数解决噪声下的相位恢复问题,确保无虚假解。

Smoothed Robust Phase Retrieval

  • 用卷积型平滑损失替代传统l1损失,改善优化几何结构。
  • 在无噪声下无虚假局部解,且梯度下降具局部线性收敛性。
  • 首次分析带任意稀疏扰动的相位恢复景观,适合信号处理研究者。

在噪声存在下,相位恢复问题旨在从一组带有稀疏但任意扰动的二次测量中恢复目标信号向量,该问题在众多科学应用中具有重要意义。然而,基于ℓ₁损失的非凸鲁棒相位恢复的本质几何结构尚未被充分理解,尤其在理想无噪声情况下也难以分析虚假局部解;其内在的非光滑特性还影响优化算法效率。本文提出基于一类卷积型平滑损失函数的平滑鲁棒相位恢复(SRPR)。理论上,我们证明了在高概率下SRPR具有良性几何结构:(1) 在无噪声情形下,SRPR无虚假局部解,目标信号为全局最优解;(2) 在稀疏但任意扰动条件下,我们刻画了SRPR的驻点性质并证明其良性景观,这是文献中首次对带扰动的相位恢复进行景观分析。此外,我们证明了在无噪声情况下梯度下降求解SRPR具有局部线性收敛速率。通过模拟数据和图像恢复实验验证了SRPR的数值性能。

原文摘要 · Abstract (English)

The phase retrieval problem in the presence of noise aims to recover the signal vector of interest from a set of quadratic measurements with infrequent but arbitrary corruptions, and it plays an important role in many scientific applications. However, the essential geometric structure of the nonconvex robust phase retrieval based on the $\ell_1$-loss is largely unknown to study spurious local solutions, even under the ideal noiseless setting, and its intrinsic nonsmooth nature also impacts the efficiency of optimization algorithms. This paper introduces the smoothed robust phase retrieval (SRPR) based on a family of convolution-type smoothed loss functions. Theoretically, we prove that the SRPR enjoys a benign geometric structure with high probability: (1) under the noiseless situation, the SRPR has no spurious local solutions, and the target signals are global solutions, and (2) under the infrequent but arbitrary corruptions, we characterize the stationary points of the SRPR and prove its benign landscape, which is the first landscape analysis of phase retrieval with corruption in the literature. Moreover, we prove the local linear convergence rate of gradient descent for solving the SRPR under the noiseless situation. Experiments on both simulated datasets and image recovery are provided to demonstrate the numerical performance of the SRPR.

相位恢复优化理论平滑损失

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