用平滑能量函数让粒子群高效跳出局部最优,找到全局解。
Global Optimization via Softmin Energy Minimization
- 引入软最小能量函数,实现梯度引导的粒子协同搜索
- 理论证明强凸函数下至少一个粒子收敛到全局最优
- 在双阱和Ackley函数上比模拟退火更快跳出局部极小
全局优化,尤其是针对具有多个局部极小值的非凸函数,对传统基于梯度的方法构成重大挑战。尽管元启发式方法在实践中表现有效,但往往缺乏理论收敛保证,且可能忽略梯度信息。本文提出一种新型基于梯度的粒子群优化方法,旨在高效逃离局部极小值并定位全局最优解。该方法利用一种“软最小能量”相互作用函数 $J_β(oldsymbol{x})$,对粒子群内最小函数值提供平滑、可微的近似。我们在粒子空间中定义了一个随机梯度流,包含布朗运动项以促进探索,并引入随时间变化的参数 $β$ 控制平滑性,类似温度退火。理论上证明:对于强凸函数,该动力学系统会收敛至一个稳态点,其中至少一个粒子达到全局最小值,其余粒子呈现探索行为。此外,我们证明该方法通过降低有效势垒,加快了在局部极小值间的转移速度,优于模拟退火。具体而言,在小噪声条件下,我们估计了未探索势阱的首次击中时间,结果表明其优于过阻尼Langevin动力学。在双阱函数和Ackley函数等基准测试中,数值实验验证了理论结果,并显示本方法在跳出局部极小和加速收敛方面优于经典的模拟退火方法。
原文摘要 · Abstract (English)
Global optimization, particularly for non-convex functions with multiple local minima, poses significant challenges for traditional gradient-based methods. While metaheuristic approaches offer empirical effectiveness, they often lack theoretical convergence guarantees and may disregard available gradient information. This paper introduces a novel gradient-based swarm particle optimization method designed to efficiently escape local minima and locate global optima. Our approach leverages a "Soft-min Energy" interacting function, $J_β(\mathbf{x})$, which provides a smooth, differentiable approximation of the minimum function value within a particle swarm. We define a stochastic gradient flow in the particle space, incorporating a Brownian motion term for exploration and a time-dependent parameter $β$ to control smoothness, similar to temperature annealing. We theoretically demonstrate that for strongly convex functions, our dynamics converges to a stationary point where at least one particle reaches the global minimum, with other particles exhibiting exploratory behavior. Furthermore, we show that our method facilitates faster transitions between local minima by reducing effective potential barriers with respect to Simulated Annealing. More specifically, we estimate the hitting times of unexplored potential wells for our model in the small noise regime and show that they compare favorably with the ones of overdamped Langevin. Numerical experiments on benchmark functions, including double wells and the Ackley function, validate our theoretical findings and demonstrate better performance over the well-known Simulated Annealing method in terms of escaping local minima and achieving faster convergence.
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