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arXiv 1405.7741math.OC
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凸优化中伪压缩更新的性质

Properties of Pseudocontractive Updates in Convex Optimization

Patrick W. Gallagher, Zhuowen Tu

摘要:

许多凸最优化方法的构思和分析在很大程度上是分开的。与这种传统的分离相反,这篇手稿指出并展示了一个重要的,但在很大程度上未被注意到的共同线程贯穿许多突出的最优化方法的效用。特别是,我们表明,方法,如连续正交投影,梯度下降,投影梯度下降,近点法,向前向后分裂,交替方向法的乘法器,和根据或过度放松的变体,前面所有涉及更新是一个共同的类型-即,更新满足一个属性称为伪收缩。此外,由于伪压缩性在复合和凸组合下都保持不变,因此通过这些操作从伪压缩更新构造的更新本身也是伪压缩的.在证明了伪压缩更新可以在许多最优化方法中找到之后,我们给出了具有伪压缩更新的方法的统一的基本分析。具体来说,我们证明了一个新的约束所满足的伪压缩更新的迭代的差异的范数,然后我们使用这个约束来建立的错误准则$\left\Vert x^{N}-Tx^{N}\right\Vert ^{2}$是$o(1/N)$的任何方法,涉及伪压缩更新(其中$N$是迭代次数和$T$是迭代算子)。

英文摘要:

Many convex optimization methods are conceived of and analyzed in a largely separate fashion. In contrast to this traditional separation, this manuscript points out and demonstrates the utility of an important but largely unremarked common thread running through many prominent optimization methods. In particular, we show that methods such as successive orthogonal projection, gradient descent, projected gradient descent, the proximal-point method, forward-backward splitting, the alternating direction method of multipliers, and under- or over-relaxed variants of the preceding all involve updates that are of a common type --- namely, the updates satisfy a property known as pseudocontractivity. Moreover, since the property of pseudocontractivity is preserved under both composition and convex combination, updates constructed via these operations from pseudocontractive updates are themselves pseudocontractive. Having demonstrated that pseudocontractive updates are to be found in many optimization methods, we then provide a unified basic analysis of methods with pseudocontractive updates. Specifically, we prove a novel bound satisfied by the norm of the difference in iterates of pseudocontractive updates and we then use this bound to establish that the error criterion $\left\Vert x^{N}-Tx^{N}\right\Vert ^{2}$ is $o(1/N)$ for any method involving pseudocontractive updates (where $N$ is the number of iterations and $T$ is the iteration operator).

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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