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arXiv 1810.04073math.NAcs.NA
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凸极小变分问题的原始-对偶缩减基方法:鲁棒真解、后验误差证明和自适应贪婪算法

Primal-Dual Reduced Basis Methods for Convex Minimization Variational Problems: Robust True Solution A Posteriori Error Certification and Adaptive Greedy Algorithms

Shun Zhang

摘要:

本文以参数对称强制椭圆边值问题为例,发展了具有鲁棒真误差证明的原-对偶变分问题,并讨论了三种贪婪算法来平衡有限元误差、精确约化基误差和自适应网格加密.对于一类凸极小化变分问题,当其对偶问题满足强对偶性时,原泛函与对偶泛函之间的原-对偶间隙可作为后验误差估计.这种原始-对偶间隙误差估计器对问题的参数是鲁棒的,它可以用于有限元法的网格加密和真实RB误差的验证。借助分部积分公式,利用共轭函数和拉格朗日理论,建立了具有非齐次边界条件的对称强制椭圆边值问题的原对偶变分理论.一个广义Prager-Synge身份,这是这个特定问题的原始-对偶间隙误差表示,开发。RBM的原始和对偶问题的鲁棒误差估计。对偶变分问题通常可以看作是一个约束最优化问题。本文通过构造满足齐次约束的RB空间,将对偶RBM作为一个Galerkin投影来处理,从而不同于标准的鞍点有限元逼近。受\cite{Yano:18}空间参数自适应贪婪算法的启发,讨论了原-对偶有限元和缩减基误差估计的自适应平衡贪婪算法。数值试验,以测试PD-RBM与自适应平衡贪婪算法。

英文摘要:

In this paper, with the parametric symmetric coercive elliptic boundary value problem as an example of the primal-dual variational problems satisfying the strong duality, we develop primal-dual reduced basis methods (PD-RBM) with robust true error certifications and discuss three versions of greedy algorithms to balance the finite element error, the exact reduced basis error, and the adaptive mesh refinements. For a class of convex minimization variational problems which has corresponding dual problems satisfying the strong duality, the primal-dual gap between the primal and dual functionals can be used as a posteriori error estimator. This primal-dual gap error estimator is robust with respect to the parameters of the problem, and it can be used for both mesh refinements of finite element methods and the true RB error certification. With the help of integrations by parts formula, the primal-dual variational theory is developed for the symmetric coercive elliptic boundary value problems with non-homogeneous boundary conditions by both the conjugate function and Lagrangian theories. A generalized Prager-Synge identity, which is the primal-dual gap error representation for this specific problem, is developed. RBMs for both the primal and dual problems with robust error estimates are developed. The dual variational problem often can be viewed as a constraint optimization problem. In the paper, different from the standard saddle-point finite element approximation, the dual RBM is treated as a Galerkin projection by constructing RB spaces satisfying the homogeneous constraint. Inspired by the greedy algorithm with spatio-parameter adaptivity of \cite{Yano:18}, adaptive balanced greedy algorithms with primal-dual finite element and reduced basis error estimators are discussed. Numerical tests are presented to test the PD-RBM with adaptive balanced greedy algorithms.

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