Leon Sallandt
Leon Sallandt is an applied mathematician whose research uses hierarchical tensors and tensor trains for high-dimensional optimal control and partial differential equations. He coauthored a stationary Bellman-equation method in November 2019, presented exit-time control work at a Max Planck Institute for Mathematics in the Sciences minisymposium in July 2020, and coauthored a policy-iteration paper on stochastic exit-time control in October 2020. In 2021, he coauthored studies on Bermudan option pricing and finite-horizon feedback controllers, and his ICML paper with Lorenz Richter and Nikolas Nüsken on parabolic PDEs received an Outstanding Paper Honorable Mention. Technische Universität Berlin accepted his doctoral thesis on high-dimensional value functions in December 2021 and issued it in 2022, and in 2024 he coauthored journal articles on stationary Bellman equations and robust regression for parabolic PDEs with a TU Berlin affiliation.
Timeline
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November 2019
A stationary Bellman solver
In November 2019, he coauthors a method for solving the stationary Hamilton-Jacobi-Bellman equation in high dimensions, using low-rank hierarchical tensor formats, including tensor trains, to approximate value functions.
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July 2020
MPI MIS low-rank minisymposium talk
In July 2020, while at Technische Universität Berlin, he presents a talk on solving stochastic exit-time control problems with tensor-train approximation at the Max Planck Institute for Mathematics in the Sciences online minisymposium on low-rank geometry and computation.
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October 2020
Exit-time feedback control with tensor trains
With Konstantin Fackeldey, Mathias Oster, and Reinhold Schneider in October 2020, he coauthors a paper on stochastic optimal exit-time feedback control driven by stochastic differential equations, solving the Bellman equation via policy iteration in the tensor-train format.
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March 2021
Bermudan option pricing
In March 2021, he and Christian Bayer, Martin Eigel, and Philipp Trunschke present a preprint on high-dimensional Bermudan option pricing with hierarchical tensors. It describes a tensor-train optimization procedure for high-dimensional polynomial expansions.
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April 2021
Finite-horizon feedback control
He coauthors a paper with Mathias Oster and Reinhold Schneider in April 2021 that applies low-rank hierarchical tensor formats to approximate optimal feedback controllers for finite-horizon control problems.
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July 2021
ICML paper award for parabolic PDEs
With Lorenz Richter and Nikolas Nüsken in July 2021, he publishes ICML work on tensor-train methods for high-dimensional parabolic PDEs, using backward stochastic differential equations and regression-based iterative schemes. The paper receives an Outstanding Paper Honorable Mention at ICML in 2021.
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December 2021–2022
A doctoral thesis on control
Technische Universität Berlin accepts his doctoral thesis on high-dimensional value functions for optimal feedback control in December 2021 and issues it in 2022. The thesis applies hierarchical tensor formats, including tensor trains, policy iteration, and Monte Carlo approximation.
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2024
Bellman and PDE journal papers
In April 2024, the Journal of Computational Mathematics publishes his stationary Bellman-equation paper with Mathias Oster and Reinhold Schneider, listing him at Technische Universität Berlin. In 2024, he also coauthors a Journal of Machine Learning Research article with Lorenz Richter and Nikolas Nüsken on tensor trains, continuous-time iterative schemes, and robust regression for backward stochastic differential equations and parabolic PDEs.
Sources and credits
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- Approximating the Stationary Bellman Equation by Hierarchical Tensor Products
- Online Minisymposium on Low-rank Geometry and Computation: MPI MIS
- Approximative Policy Iteration for Exit Time Feedback Control Problems driven by Stochastic Differential Equations using Tensor Train format
- Pricing high-dimensional Bermudan options with hierarchical tensor formats
- Approximating optimal feedback controllers of finite horizon control problems using hierarchical tensor formats
- Solving high-dimensional parabolic PDEs using the tensor train format
- ICML 2021 Awards
- Computing high-dimensional value functions of optimal feedback control problems using the Tensor-train format
- Approximating the Stationary Bellman Equation by Hierarchical Tensor Products
- From continuous-time formulations to discretization schemes: tensor trains and robust regression for BSDEs and parabolic PDEs