arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2011.01369cs.ITmath.IT

基于升尺度向量近似消息传递的压缩感知

Compressed Sensing with Upscaled Vector Approximate Message Passing

Nikolajs Skuratovs, Michael Davies

AI总结:

针对VAMP算法因高计算量LMMSE估计难以应用于大规模问题的局限,提出用共轭梯度近似LMMSE并设计热启动方案,构建WS-CG-VAMP算法,实验证明其在大规模图像重建中效率和效果更优。

摘要:

近期提出的向量近似消息传递(Vector Approximate Message Passing, VAMP)算法在求解压缩感知相关的线性逆问题时展现出出色的重建潜力。VAMP单次迭代的提升效果显著,可利用BM3D等强大的去噪器,具有严格定义的动力学特性,还能恢复由高度欠采样、病态线性算子测量得到的信号。但由于每次迭代都需要计算计算量极大的线性最小均方误差(Linear Minimum Mean Square Error, LMMSE)估计器,其适用性局限于规模相对较小的问题。本研究针对VAMP的升尺度问题,采用共轭梯度(Conjugate Gradient, CG)方法来近似难以求解的LMMSE估计器。我们提出了一种严格的方法,用于在CG-VAMP框架内校正和调优CG,以实现稳定且高效的重建。为进一步提升CG-VAMP的性能,我们为CG设计了一种热启动方案,并建立了热启动CG-VAMP(Warm-Started CG-VAMP, WS-CG-VAMP)的Onsager校正与状态演化的理论模型。此外,我们还开发了实现WS-CG-VAMP算法的鲁棒且精准的方法。针对大规模图像重建问题的数值实验表明,与CG-VAMP相比,WS-CG-VAMP仅需少得多的CG迭代次数,就能达到同等甚至更优的重建水平。

英文摘要:

The Recently proposed Vector Approximate Message Passing (VAMP) algorithm demonstrates a great reconstruction potential at solving compressed sensing related linear inverse problems. VAMP provides high per-iteration improvement, can utilize powerful denoisers like BM3D, has rigorously defined dynamics and is able to recover signals measured by highly undersampled and ill-conditioned linear operators. Yet, its applicability is limited to relatively small problem sizes due to the necessity to compute the expensive LMMSE estimator at each iteration. In this work we consider the problem of upscaling VAMP by utilizing Conjugate Gradient (CG) to approximate the intractable LMMSE estimator. We propose a rigorous method for correcting and tuning CG withing CG-VAMP to achieve a stable and efficient reconstruction. To further improve the performance of CG-VAMP, we design a warm-starting scheme for CG and develop theoretical models for the Onsager correction and the State Evolution of Warm-Started CG-VAMP (WS-CG-VAMP). Additionally, we develop robust and accurate methods for implementing the WS-CG-VAMP algorithm. The numerical experiments on large-scale image reconstruction problems demonstrate that WS-CG-VAMP requires much fewer CG iterations compared to CG-VAMP to achieve the same or superior level of reconstruction.

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