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arXiv 2006.01231math.NAcs.NAmath.OC
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MG/OPT和MLMC用于PDE的稳健Optimization

MG/OPT and MLMC for Robust Optimization of PDEs

Andreas Van Barel, Stefan Vandewalle

摘要:

基于MG/OPT框架,提出了一种求解不确定系数偏微分方程约束鲁棒控制问题的算法。这个MG/OPT层次结构中的级别通常对应于PDE的离散化级别。对于随机问题,相关的量(如梯度)包含这些水平上的每一个期望值算子。使用多水平蒙特卡罗方法估计,具体取决于MG/OPT水平。然后,每个优化级别包含多个底层多级蒙特卡罗级别。MG/OPT层次结构允许算法利用PDE中固有的结构,加速收敛到最优。相比之下,多级蒙特卡洛层次结构的存在,利用结构中存在的随机尺寸的问题。证明了算法的收敛速率,并讨论了算法的一些性质。该算法的性能进行了数值研究的三个测试用例。可以观察到在昂贵的水平上所需的样本的样本个数的减少以及因此在计算时间上的减少。

英文摘要:

An algorithm is proposed to solve robust control problems constrained by partial differential equations with uncertain coefficients, based on the so-called MG/OPT framework. The levels in this MG/OPT hierarchy correspond to discretization levels of the PDE, as usual. For stochastic problems, the relevant quantities (such as the gradient) contain expected value operators on each of these levels. They are estimated using a multilevel Monte Carlo method, the specifics of which depend on the MG/OPT level. Each of the optimization levels then contains multiple underlying multilevel Monte Carlo levels. The MG/OPT hierarchy allows the algorithm to exploit the structure inherent in the PDE, speeding up the convergence to the optimum. In contrast, the multilevel Monte Carlo hierarchy exists to exploit structure present in the stochastic dimensions of the problem. A statement about the rate of convergence of the algorithm is proven, and some additional properties are discussed. The performance of the algorithm is numerically investigated for three test cases. A reduction in the number of samples required on expensive levels and therefore in computational time can be observed.

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