14 papers
Primal-dual multigrid methods for nonsmooth optimization
Felipe Guerra, Tuomo Valkonen
In optimization, one often encounters problems of the form . In this work, we combine primal-dual algorithms with multigrid techniques for their solution. T…
Single-loop approaches to nonsmooth bilevel optimisation
Ensio Suonperä, Tuomo Valkonen
We study bilevel optimisation problems in which the inner problem is represented as a set-valued, parametric constraint. We develop relevant optimistic and pessimistic calculus rul…
Dynamic inverse problems: Single-loop online algorithms
Jyrki Jauhiainen, Yassine Nabou, Tuomo Valkonen
We study efficient online methods for dynamic inverse problems with infinite time horizon. We concentrate, in particular, on problems whose forward model arises from a PDE. Our mot…
Dynamic inverse problems: Online regularisation theory
Jyrki Jauhiainen, Yassine Nabou, Tuomo Valkonen
We develop regularisation theory for dynamic inverse problems, solved using online methods with an infinite time horizon. Using concepts of subregularity to treat nonsmooth regular…
Leak localisation with a measure source convection-diffusion model
Thi Tam Dang, Tuomo Valkonen
We study the inverse problem of locating gas leaks from line-of-sight concentration measurements using a convection-diffusion model with the source term a Radon measure. By imposin…
Introduction to Nonsmooth Analysis and Optimization
Christian Clason, Tuomo Valkonen
Functions that are not differentiable in the classical sense have become a central tool in modern mathematical models for imaging, inverse problems, machine learning, and optimal c…