• 《不确定性DC规划问题的研究》
  • 作者:沈开基著
  • 单位:上海财经大学
  • 论文名称 不确定性DC规划问题的研究
    作者 沈开基著
    学科 应用概率
    学位授予单位 上海财经大学
    导师 王燕军指导
    出版年份 2019
    中文摘要 DC(Difference of Convex functions)规划最早是在1985年由Pham Dinh Tao提出的.一些重要的理论研究和算法研究在1994年逐步开始成熟,DC规划也慢慢开始受到广大学者们的高度关注.在定性和定量上,它独特的结构提供了长远并且具有意义的研究空间.在实际应用DC规划过程中,研究人员发现数据本身往往具有不确定性或者随机性,本文主要研究多种情况下带不确定性或者带随机变量DC规划问题的性质和算法. 我们首先对一类已知样本信息带随机变量的DC规划进行详细讨论.由于DC规划本身是一个非凸问题,所以我们构造了一种新函数:Concave-R函数,并且证明通过Concave-R函数构造的凹逼近是最紧的.我们还分别构造带鲁棒性的RDDC模型和CVaR下的CVaR-DC模型,并且证明了当参数趋于1时,带鲁棒性RDDC的最优值和CVaR下CVaR-DC的最优值是相等的.在分支定界算法框架下借助Concave-R函数分别设计了对带鲁棒性的RDDC模型和CVaR下的CVaR-DC模型的算法.对于带联合概率约束的DC规划,证明通过Bonferroni不等式构造的凸逼近方法优于其他方法.数值实验部分也验证了上述结论. 其次我们讨论了在l〓-Wasserstein距离下带随机性的DC规划问题.当p= 1时,无论是左随机变量还是右随机变量,原问题都可以转为可求解的0-1混合整数规划问题.由于混合整数规划是NP难问题,所以我们对原问题进行凸逼近并且设计可求解的凸规划算法.当p=2时,对于离散的情况,我们将原问题等价转为0-1整数规划;对于连续的情况,我们先证明原问题与min max模型等价,然后利用锥对偶定理将规划问题转化为可求解的0-1 SOCP混合整数规划问题.最后应用上述的结果子带随机性的SVM模型,数值实验表明我们的算法是可行且有效的. 最后利用共轭函数的性质,我们构建了可求解的在PE散度下带概率约束DC规划模型.同时对一般Φ-散度进行拓展,定义了一种新的概念:Quasi-Φ差别,用来衡量真实概率和根据样本推测经验概率之间的差别.借助共轭函数和拉格朗日对偶的性质,建立了在Quasi-Φ差别下带随机变量的DC规划模型并且计算证明了Quasi-Φ差别的VoD(Value ofData)值的特殊性.也就是当距离参数趋于0时,新模型中的置信水平趋向于原模型中的置信水平.数值实验表明在分类准确率相接近的情况下,和经典的SVM模型相比我们的模型方差更小,更加具有鲁棒性质. 关键词:DC规划,Concave-R函数,鲁棒性,Wasserstein距离,Φ-散度.
    英文摘要 DC programming is a very important problem in non-convex programming. DC programming was first proposed by Pham Dinh Tao in 1985. Some important theoretical and algorithmic studies began to mature in 1994, and DC programming gradually began to attract great attention. Due to its excellent characteristics, its unique structure provides a long-term and meaningful research space. In the process of applying DC programming, researchers find that the data is often uncertain or random, so this paper mainly studies the algorithms and properties of DC programming with randomness in various situations. We first discuss a class of DC programming with random variables when sample is known in detail. Since DC programming itself is a non-convex problem, we construct a new function Concave-R function and prove that the concave approximation constructed by the Concave-R function is the most compact. We also construct the RDDC model with robustness and the CVaR-DC model with CVaR, respectively. We also prove that when the parameters tend to converge, the model with robustness RDDC and the model with robustness CVaR-DC under CVaR are equivalent. In the framework of branch-and-bound algorithm, Concave-R function is used to design specific algorithms for the model with robustness RDDC and the model with robustness CVaR-DC under CVaR, respectively. With the help of the Bonferroni inequality, we also construct a new convex approximation form of DC programming with joint probability constraints. Then we discuss the DC programming under the l〓-Wasserstein distance with randomness . We mainly study the case of p = 1 and p = 2. For l₁-Wasserstein DC programming with randomness, whether left or right random variables, the original problem can be transformed into a 0-1 mixed integer programming problem. Because mixed integer programming is a NP hard problem, we try to develop a new algorithm which will helps us to solve the model in polynomial time. When p = 2, the original problem is transformed into a solvable 0-1 mixed integer SOCP programming problem by using the cone duality theorem. Applying the above results to the SVM model with randomness, numerical experiments show that our algorithm is feasible and effective. Finally, we discuss DC programming with random variables under Φ-divergence. By using the properties of conjugate function, we construct a solvable DC programming model with random variables under Pearson divergence. At the same time, we extend the general Φ-divergence and define a new concept: Quasi-Φ difference to measure the difference between real probability and empirical probability based on samples. The DC programming model with random variables under the difference of Quasi-Φ is established and the VoD (Value of Data) value of Quasi-Φ difference is proved by calculation. That is, when the distance parameter approaches zero, the confidence level of the new model tends to the confidence level of the original model. The numerical experiments show that when the accuracy between classical one and ours are similar, in this case, our model has smaller variance and more robustness. KEYWORDS: DC programming, Concave-R function, Robustness, Wasserstein distance, Φ-divergence.
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