Convergence analysis of alternating direction method of multipliers for a family of nonconvex problems

In this paper, we analyze the behavior of the alternating direction method of multipliers (ADMM), for solving a family of nonconvex problems. Our focus is given to the well-known consensus and sharing problems, both of which have wide applications in signal processing. We show that in the presence of nonconvex objective function, classical ADMM is able to reach the set of stationary solutions for these problems, if the stepsize is chosen large enough. An interesting consequence of our analysis is that the ADMM is convergent for a family of sharing problems, regardless of the number of blocks or the convexity of the objective function. Our analysis is broadly applicable to many ADMM variants involving proximal update rules and various flexible block selection rules.