THE ADMM-PINNS ALGORITHMIC FRAMEWORK FOR NONSMOOTH PDE-CONSTRAINED OPTIMIZATION: A DEEP LEARNING APPROACH

We study the combination of the alternating direction method of multipliers (ADMM) with physics-informed neural networks (PINNs) for a general class of nonsmooth partial differential equation (PDE)-constrained optimization problems, where additional regularization can be employed for constraints on the control or design variables. The resulting ADMM-PINNs algorithmic framework substantially enlarges the applicable range of PINNs to nonsmooth cases of PDE-constrained optimization problems. The application of the ADMM makes it possible to separate the PDE constraints and the nonsmooth regularization terms for iterations. Accordingly, at each iteration, one of the resulting subproblems is a smooth PDE-constrained optimization which can be efficiently solved by PINNs, and another is a simple nonsmooth optimization problem, which usually has a closed-form solution or can be efficiently solved by various standard optimization algorithms or pretrained neural networks. The ADMM-PINNs algorithmic framework does not require one to solve PDEs repeatedly, and it is mesh-free, easy to implement, and scalable to different PDE settings. We validate the efficiency of the ADMM-PINNs algorithmic framework by different prototypical applications, including inverse potential problems, source identification in elliptic equations, control constrained optimal control of the Burgers equation, and sparse optimal control of parabolic equations.