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Deterministic control of randomly-terminated processes. (English) Zbl 1292.49027

Summary: We consider both discrete and continuous “uncertain horizon” deterministic control processes, for which the termination time is a random variable. We examine the dynamic programming equations for the value function of such processes, explore their connections to infinite-horizon and optimal-stopping problems, and derive sufficient conditions for the applicability of non-iterative (label-setting) methods. In the continuous case, the resulting PDE has a free boundary, on which all characteristic curves originate. The causal properties of “uncertain horizon” problems can be exploited to design efficient numerical algorithms: we derive causal semi-Lagrangian and Eulerian discretizations for the isotropic randomly-terminated problems, and use them to build a modified version of the fast marching method. We illustrate our approach using numerical examples from optimal idle-time processing and expected response-time minimization.

MSC:

49L20 Dynamic programming in optimal control and differential games
49K45 Optimality conditions for problems involving randomness
49L25 Viscosity solutions to Hamilton-Jacobi equations in optimal control and differential games
93E20 Optimal stochastic control
35R35 Free boundary problems for PDEs
60G40 Stopping times; optimal stopping problems; gambling theory
65N22 Numerical solution of discretized equations for boundary value problems involving PDEs
90C39 Dynamic programming
05C85 Graph algorithms (graph-theoretic aspects)