用随机控制方法求解非凸非光滑优化问题,无需梯度。
Stochastic Control Methods for Optimization
- 通过正则化随机控制框架,将优化转化为可解的动态规划问题。
- 理论证明:正则化参数趋近零时,解收敛到全局最小值。
- 基于蒙特卡洛模拟,无需梯度即可计算,适合复杂目标函数。
本文研究了在欧几里得空间和概率测度的Wasserstein空间上进行全局优化的随机控制框架,目标函数可为非凸且不可导。在欧氏空间中,原最小化问题被近似为一族正则化的随机控制问题;利用动态规划,分析相关的哈密顿-雅可比-贝尔曼方程,通过Cole-Hopf变换和Feynman-Kac公式获得可处理的表示形式。对于概率测度上的优化,构建了一个由主方程刻画的正则化平均场控制问题,并进一步用受控的N粒子系统逼近。我们证明:当正则化参数趋于零(且对概率测度优化,粒子数趋于无穷时),控制问题的值收敛至原目标函数的全局最小值。基于所得的概率表示,提出基于蒙特卡洛的无梯度数值算法,利用Bismut-Elworthy-Li公式实现。数值实验验证了方法的有效性,并支持理论收敛速率。
原文摘要 · Abstract (English)
In this work, we investigate a stochastic control framework for global optimization over both Euclidean spaces and the Wasserstein space of probability measures, where the objective function may be non-convex and/or non-differentiable. In the Euclidean setting, the original minimization problem is approximated by a family of regularized stochastic control problems; using dynamic programming, we analyze the associated Hamilton-Jacobi-Bellman equations and obtain tractable representations via the Cole-Hopf transformation and the Feynman-Kac formula. For optimization over probability measures, we formulate a regularized mean-field control problem characterized by a master equation, and further approximate it by controlled $N$-particle systems. We establish that, as the regularization parameter tends to zero (and as the particle number tends to infinity for the optimization over probability measures), the value of the control problem converges to the global minimum of the original objective. Building on the resulting probabilistic representations, we propose the Monte Carlo-based numerical schemes that are derivative-free due to the utilization of the Bismut-Elworthy-Li formula and numerical experiments are reported to illustrate the effectiveness of the methods and to support the theoretical convergence rates.
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