arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 0802.3922math.OC
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约束共识

Constrained Consensus

Angelia Nedić, Asuman Ozdaglar, Pablo A. Parrilo

摘要:

我们提出了分布式算法,可用于多个代理,以调整他们的估计与一个特定的值在网络随时间变化的连接。我们的框架是通用的,因为该值可以表示多个代理之间的共识值或最优化问题的最优解,其中全局目标函数是局部代理目标函数的组合。我们的主要重点是约束问题,其中每个代理的估计被限制在一个不同的约束集。为了突出约束的影响,我们首先考虑一个受约束的共识问题,并提出了一个分布式的“投影共识算法”,在该算法中,代理将其本地平均操作与其各自约束集的投影相结合。该算法可以被视为交替投影方法的一个版本,其权重随时间和代理而变化。我们建立了收敛性和收敛速度的结果投影共识算法。接下来,我们研究了一个约束最优化问题,用于优化受其局部约束集相交的代理的局部目标函数的总和。我们提出了一个分布式的"投影次梯度法“,它涉及到每个代理执行一个本地平均操作,采取一个次梯度步骤,以最小化自己的目标函数,并投影在其约束集。我们表明,与适当选择的步长规则,该算法产生的代理估计收敛到相同的最优解的情况下,当权重是恒定的和平等的,当权重是随时间变化的,但所有的代理有相同的约束集。

英文摘要:

We present distributed algorithms that can be used by multiple agents to align their estimates with a particular value over a network with time-varying connectivity. Our framework is general in that this value can represent a consensus value among multiple agents or an optimal solution of an optimization problem, where the global objective function is a combination of local agent objective functions. Our main focus is on constrained problems where the estimate of each agent is restricted to lie in a different constraint set. To highlight the effects of constraints, we first consider a constrained consensus problem and present a distributed ``projected consensus algorithm'' in which agents combine their local averaging operation with projection on their individual constraint sets. This algorithm can be viewed as a version of an alternating projection method with weights that are varying over time and across agents. We establish convergence and convergence rate results for the projected consensus algorithm. We next study a constrained optimization problem for optimizing the sum of local objective functions of the agents subject to the intersection of their local constraint sets. We present a distributed ``projected subgradient algorithm'' which involves each agent performing a local averaging operation, taking a subgradient step to minimize its own objective function, and projecting on its constraint set. We show that, with an appropriately selected stepsize rule, the agent estimates generated by this algorithm converge to the same optimal solution for the cases when the weights are constant and equal, and when the weights are time-varying but all agents have the same constraint set.

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