针对非凹效用函数,提出新算法解决二阶随机占优约束下的投资组合优化问题。
Stochastic Dominance Constrained Optimization with S-shaped Utilities: Poor-Performance-Region Algorithm and Neural Network
- 通过识别差表现区域并调整分布,设计数值求解算法。
- 在多个案例中有效找到次优解,验证算法可行性。
- 结合神经网络框架,收敛速度优于传统方法,适合金融风险管理场景。
研究在一阶和二阶随机占优(SD)约束下,具有S型且非凹效用函数的静态投资组合选择问题。许多S型效用优化问题需设定清算边界以保证有限凹包络函数存在,而一阶随机占优(FSD)约束可替代该要求,提供风险管控的新途径。本文显式求解了一般S型效用函数在FSD约束下的最优解。然而,由于Sion极大极小定理失效,非凹效用下的二阶随机占优(SSD)约束问题难以解析求解。为此,我们提出一种数值算法,通过检测与SSD约束相关的差表现区域,刻画其结构,并修改该区域分布以获得(次)最优解。关键金融洞见是:决策者应在差表现情景下遵守SD约束,其他情形则采用无约束最优策略。数值实验表明,该算法在多类问题中能有效找到次优解。最后,我们构建了算法引导的分段神经网络框架,学习SSD问题的解,相比标准神经网络方法展现出更快收敛性。
原文摘要 · Abstract (English)
We investigate the static portfolio selection problem of S-shaped and non-concave utility maximization under first-order and second-order stochastic dominance (SD) constraints. In many S-shaped utility optimization problems, one should require a liquidation boundary to guarantee the existence of a finite concave envelope function. A first-order SD (FSD) constraint can replace this requirement and provide an alternative for risk management. We explicitly solve the optimal solution under a general S-shaped utility function with a first-order stochastic dominance constraint. However, the second-order SD (SSD) constrained problem under non-concave utilities is difficult to solve analytically due to the invalidity of Sion's maxmin theorem. For this sake, we propose a numerical algorithm to obtain a plausible and sub-optimal solution for general non-concave utilities. The key idea is to detect the poor performance region with respect to the SSD constraints, characterize its structure and modify the distribution on that region to obtain (sub-)optimality. A key financial insight is that the decision maker should follow the SD constraint on the poor performance scenario while conducting the unconstrained optimal strategy otherwise. We provide numerical experiments to show that our algorithm effectively finds a sub-optimal solution in many cases. Finally, we develop an algorithm-guided piecewise-neural-network framework to learn the solution of the SSD problem, which demonstrates accelerated convergence compared to standard neural network approaches.
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