OPTIMIZATION, cilt.71, sa.11, ss.3133-3146, 2022 (SCI-Expanded)
In this work, we provide discrete optimality conditions of the optimal control problems of stochastic differential equations. Euler and Runge-Kutta methods are used for discretization. A Lagrange multiplier method for a discrete-time stochastic optimal control problem is formulated. The discrete adjoint process pn is obtained in terms of conditional expectations E[p(n+1)] and E[p(n+1)Delta W] for both methods. To estimate these nested conditional expectations at each time step via simulation, we use a very powerful new approach, least-squares Monte-Carlo method, developed by Longstaff- Schwartz. This is the first time to solve a stochastic optimal control problem by calculating the nested conditional expectations numerically with the help of a least-squares Monte-Carlo method. Some examples are studied to test and demonstrate the efficiency of the Lagrange multiplier combined with the leastsquares Monte-Carlo method.