随机模拟的一些新进展
Some Recent Advances in Stochastic Simulation
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摘要: 此综述文章介绍随机模拟方面的两个新进展: 构造小概率事件估计的有效算法, 产生形式不封闭的平稳分布的样本. 估计一个非常小的量, 需要极其准确地取定一个有用的置信区间. 这使得慢收敛的小概率事件模拟在有效性和准确性两方面都成为具有挑战性的任务. 在此文中, 我们介绍一些有趣的小概率事件例子以及在估计它们时的困难所在. 然后沿着发展脉络, 寻求稳健且有效的估计量的各种方法将被讨论和评估. 估计破产概率的数值实验则用来显示这些方法的质量. 在稳定态模拟中, 如何产生平稳随机过程的样本长期以来是一个关键性课题. 通常的做法是在初始的短暂时期内丢弃掉所得数据. 然而, 热身准备必须多长时间则成为另一个没有满意答案的问题. 幸运地, 经过过去二十年的发展, 对一些特定的随机模型, 精确模拟已经成为可能. 在此文中, 我们将介绍两个重要的方法及其相关的应用.Abstract: This review article introduces two recent advances in stochastic simulation: the construction of efficient algorithms for estimating rare events and the generation of samples from a stationary distribution that has no closed form. Estimating a very small quantity requires extreme accuracy to form a useful confidence interval. This makes the slowly convergent rare-event simulation a challenge task in both efficiency and accuracy. In this report, we introduce the examples of rare events of interest and the difficulties in estimating them. Various approaches to pursue robust and efficient estimators along the development are discussed and evaluated. Numerical experiments on estimating ruin probability are provided to show the quality of these approaches. In steady-state simulation, how to generate samples from a stationary stochastic process has long been the key subject. The common practice is to discard the data gathered during the initial transient period. However, how long the warm-up period must be raises another problem that has no satisfactory answer. Fortunately, by the development in the past two decades, exact simulation has become possible for certain stochastic models. In this report, we will introduce two important methods and related applications.