An ADMM-SQP FALF-Based Method for Two-Block Nonconvex Optimization with Linear Equality-Inequality Constraints
摘要
It is known that the sequential quadratic programming (SQP) method and the alternating direction method of multipliers (ADMM) are two kinds of very effective tools for solving smooth small-to-medium-scale optimization and large-scale separable optimization, respectively. This paper discusses a class of large-scale two-block optimization problems with linear equality-inequality constraints, where the objective function is smooth but not necessarily convex. Our aim is to design a novel ADMM-SQP method based on the fully augmented Lagrangian function (FALF for short, namely, both the equality constraints and the inequality constraints are considered in the augmented Lagrangian function). The main technical routes are as follows. First, based on FALF technique, transform the quadratic programming (QP) subproblem associated with the original problem to a piecewise QP (PQP) subproblem with simple constraints. Second, use the Gauss-Seidel splitting to divide the PQP into two small-scale PQP subproblems. And then, by linearizing the piecewise quadratic objective, reduce the PQP subproblems to two standard QP subproblems, which can yield two improved search directions corresponding to the primal two-block variables. Third, with the FALF of the original problem as a merit function, along the improved search directions, execute Armijo line search to generate the new iteration point. Fourth, the multipliers are updated by a new scheme different from ADMM. Based on a key inequality established in this paper, the global convergence and