Distributed constrained optimization via continuous-time mirror design

Recently, distributed convex optimization using a multiagent system has received much attention by many researchers. This problem is frequently approached by combing the consensus algorithms in the multiagent literature and the gradient algorithms in the convex optimization literature. Compared with unconstrained distributed optimization, the constrained case is more challenging, and it is usually tackled by the projected gradient method. However, the projected gradient algorithm involves projection nonlinearity and thus is hard to analyze. To avoid gradient projection, in this paper, we present a novel distributed convex optimization algorithm in continuous time by using mirror design. The resulting optimization dynamics is smooth without using gradient projection and is designed in a primal-dual framework, where the primal and dual dynamics are respectively aided by the mirror descent and the mirror ascent. As for the merit of mirror design in our paper, it avoids gradient projection in the optimization dynamics design and removes the difficulty of analyzing projection nonlinearity. Furthermore, the mirror base primal-dual optimization dynamics facilitates more convenience construction of Lyapunov functions in the stability analysis.