Towards Matrix-Free AD-Based Preconditioning of KKT Systems in PDE-Constrained Optimization

Towards Matrix-Free AD-Based Preconditioning of KKT Systems in PDE-Constrained Optimization

The presented approach aims at solving an equality constrained, finite-dimensional optimization problem, where the constraints arise from the discretization of some partial differential equation (PDE) on a given space grid. For this purpose, a stationary point of the Lagrangian is computed using Newton’s method, which requires the repeated solution of KKT systems. The proposed algorithm focuses...

All-at-once preconditioning in PDE-constrained optimization

The optimization of functions subject to partial differential equations (PDE) plays an important role in many areas of science and industry. In this paper we introduce the basic concepts of PDE-constrained optimization and show how the all-at-once approach will lead to linear systems in saddle point form. We will discuss implementation details and different boundary conditions. We then show how...

Preconditioning KKT systems §

Standard preconditioners, such as ILU factorizations, often break down in construction for KKT matrices. We compare several approaches for preconditioning KKT systems. The first applies a constraint preconditioner by incorporating robust factored approximations of (BB ) and BB , where B is the (2,1) block of the KKT matrix. In the second approach, we apply permutations and scalings that maximiz...

Lectures Notes Algorithms and Preconditioning in PDE-Constrained Optimization

Preconditioning PDE-constrained optimization with L1-sparsity and control constraints

PDE-constrained optimization aims at finding optimal setups for partial differential equations so that relevant quantities are minimized. Including sparsity promoting terms in the formulation of such problems results in more practically relevant computed controls but adds more challenges to the numerical solution of these problems. The needed L1-terms as well as additional inclusion of box cont...