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arXiv 2201.02608math.OC
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QN Optimization,带粗麻布样品

QN Optimization with Hessian Sample

Joy Azzam, Daniel Henderson, Benjamin Ong, Allan Struthers

摘要:

本文探讨了如何有效地将曲率信息产生的SIMD并行前向模式微分(AD)到无约束拟牛顿(QN)最小化的光滑目标函数,$f$。具体地,每当评估梯度时,前向模式AD可以用于生成块海森样本$Y=\nabla^2 f(x)\,S$。块QN算法然后用这些海森样本更新近似逆海森样本$H_k \approx \nabla^2 f(x_k)$。而标准的线搜索为基础的BFGS算法仔细过滤和纠正割线为基础的近似曲率信息,以保持正定近似,我们的算法直接将海森样本更新不确定的逆海森近似过滤。采样方向补充标准QN二维信赖域子问题,生成一个中等规模的子问题,可以利用负曲率。由此产生的二次约束二次规划精确求解的广义本征值算法和步骤先进的标准置信域步骤接受和半径调整。本文的目的是避免串行瓶颈,利用准确的正,负曲率信息,并进行初步评估的选择策略$S$。

英文摘要:

This article explores how to effectively incorporate curvature information generated using SIMD-parallel forward-mode Algorithmic Differentiation (AD) into unconstrained Quasi-Newton (QN) minimization of a smooth objective function, $f$. Specifically, forward-mode AD can be used to generate block Hessian samples $Y=\nabla^2 f(x)\,S$ whenever the gradient is evaluated. Block QN algorithms then update approximate inverse Hessians, $H_k \approx \nabla^2 f(x_k)$, with these Hessian samples. Whereas standard line-search based BFGS algorithms carefully filter and correct secant-based approximate curvature information to maintain positive definite approximations, our algorithms directly incorporate Hessian samples to update indefinite inverse Hessian approximations without filtering. The sampled directions supplement the standard QN two-dimensional trust-region sub-problem to generate a moderate dimensional subproblem which can exploit negative curvature. The resulting quadratically-constrained quadratic program is solved accurately with a generalized eigenvalue algorithm and the step advanced using standard trust region step acceptance and radius adjustments. The article aims to avoid serial bottlenecks, exploit accurate positive and negative curvature information, and conduct a preliminary evaluation of selection strategies for $S$.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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