论文标题
非本地演算的优化和学习
Optimization and Learning With Nonlocal Calculus
论文作者
论文摘要
非局部模型最近对非线性连续性力学产生了重大影响,并用于描述物理系统/过程,这些系统/过程无法通过基于经典的微积分的“局部”方法准确地描述。在某种程度上,这是由于它们的多尺寸性,使微观行为的聚集能够获得奇异/不规则现象的宏观描述,例如Peridyanic,裂纹繁殖,异常扩散和转运现象。这些模型的核心是非局部差分运算符,包括梯度/黑森的非局部类似物。本文在优化和学习的背景下启动了此类非本地运营商的使用。我们定义和分析(随机)梯度下降的非局部类似物的收敛性和牛顿在欧几里德空间上的方法。我们的结果表明,随着非局部相互作用变得不那么明显,与非局部优化相对应的最优值会收敛到“常规” Optima。同时,我们认为在标准演算失败的情况下,非本地学习是可能的。作为此类程式化的数值示例,我们考虑了非平滑翻译歧管上非差异参数估计的问题,并表明我们的非局部梯度下降从非不同的目标函数中恢复了未知的翻译参数。
Nonlocal models have recently had a major impact in nonlinear continuum mechanics and are used to describe physical systems/processes which cannot be accurately described by classical, calculus based "local" approaches. In part, this is due to their multiscale nature that enables aggregation of micro-level behavior to obtain a macro-level description of singular/irregular phenomena such as peridynamics, crack propagation, anomalous diffusion and transport phenomena. At the core of these models are nonlocal differential operators, including nonlocal analogs of the gradient/Hessian. This paper initiates the use of such nonlocal operators in the context of optimization and learning. We define and analyze the convergence properties of nonlocal analogs of (stochastic) gradient descent and Newton's method on Euclidean spaces. Our results indicate that as the nonlocal interactions become less noticeable, the optima corresponding to nonlocal optimization converge to the "usual" optima. At the same time, we argue that nonlocal learning is possible in situations where standard calculus fails. As a stylized numerical example of this, we consider the problem of non-differentiable parameter estimation on a non-smooth translation manifold and show that our nonlocal gradient descent recovers the unknown translation parameter from a non-differentiable objective function.