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تسجيل مستخدم جديدAccelerated Decentralized Dual Averaging
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This paper studies decentralized convex optimization problems defined over networks, where the objective is to minimize a sum of local smooth convex functions while respecting a common constraint. Two new algorithms based on dual averaging and decentralized consensus-seeking are proposed. The first one accelerates the standard convergence rate $O(frac{1}{sqrt{t}})$ in existing decentralized dual averaging (DDA) algorithms to $O(frac{1}{t})$, where $t$ is the time counter. This is made possible by a second-order consensus scheme that assists each agent to locally track the global dual variable more accurately and a new analysis of the descent property for the mean variable. We remark that, in contrast to its primal counterparts, this method decouples the synchronization step from nonlinear projection, leading to a rather concise analysis and a natural extension to stochastic networks. In the second one, two local sequences of primal variables are constructed in a decentralized manner to achieve acceleration, where only one of them is exchanged between agents. In addition to this, another consensus round is performed for local dual variables. The convergence rate is proved to be $O(1)(frac{1}{t^2}+frac{1}{t})$, where the magnitude of error bound is showed to be inversely proportional to the algebraic connectivity of the graph. However, the condition for stepsize does not rely on the weight matrix associated with the graph, making it easier to satisfy in practice than other accelerated methods. Finally, comparisons between the proposed methods and several recent algorithms are performed using a large-scale LASSO problem.
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