提出矩阵值优化的混合设计,提升约束优化稳定性与收敛性。
Matrix-Valued Optimism is Matrix-Valued Augmentation: Additive Hybrid Designs for Constrained Optimization
- 将增广拉格朗日与乐观对偶方法统一为矩阵修正叠加机制
- 混合设计在非线性约束问题上优于纯增广或纯乐观方法
- 适合处理条件数中等偏高的约束优化问题
增广拉格朗日与乐观原-对偶方法通过不同机制稳定等式约束优化:前者添加依赖约束的原始曲率,后者添加对偶记忆。近期工作表明,对标量参数这两种机制等价。本文将其扩展至矩阵值修正。证明了可加性原理:对称矩阵参数下,理想原始轨迹仅取决于修正矩阵的总和,而非其在增广与乐观通道间的分配。这一发现带来设计自由度:代数等价的分解可能因增广修正影响原始曲率、乐观修正影响对偶记忆尺度,导致有限步可行性差异。我们构建了步长受限的设计问题,并推导出闭式混合规则,根据局部谱权重选择并拆分矩阵修正,同时确定原始与对偶步长。在控制约束雅可比条件数的非线性等式约束问题上的实验显示,该混合设计优于纯增广与纯乐观终点,接近网格搜索混合基准,且在温和至中等病态条件下优于一阶原-对偶基线。实验也揭示预期局限:随着约束雅可比变得病态,精确抵消需更大的矩阵修正。
原文摘要 · Abstract (English)
Augmented Lagrangian and optimistic primal--dual methods stabilize equality-constrained optimization through seemingly different mechanisms: the former adds constraint-dependent primal curvature, while the latter adds dual memory. Recent work has shown that these mechanisms are equivalent for scalar parameters. We extend this equivalence to matrix-valued correction. We prove an additivity principle: for symmetric matrix parameters, the ideal primal trajectory depends only on the summed correction matrix, not on how it is split between augmented and optimistic channels. This exposes a design freedom: algebraically equivalent decompositions can have different finite-step feasibility because augmented correction affects primal curvature, whereas optimistic correction affects the scale of the dual memory correction. We formulate the resulting step-size-limited design problem and derive a closed-form hybrid rule that selects a matrix correction, splits it between the two channels, and chooses primal and dual steps using local spectral weights. Experiments on nonlinear equality-constrained problems with controlled constraint-Jacobian conditioning show that the hybrid design improves over pure augmented and pure optimistic endpoints, closely tracks a grid-search hybrid oracle, and is competitive with first-order primal--dual baselines under mild-to-moderate ill-conditioning. The experiments also identify the expected limitation: exact cancellation requires increasingly large matrix corrections as the constraint Jacobian becomes ill-conditioned.
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