arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2202.02682math.NAcs.NAmath.STstat.TH
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通过活动子空间的预积分

Pre-integration via Active Subspaces

Sifan Liu, Art B. Owen

摘要:

预积分是条件蒙特卡罗方法向拟蒙特卡罗方法和随机拟蒙特卡罗方法的推广。它可以减少而不是增加蒙特卡罗的方差。对于拟蒙特卡罗方法,它可以带来改进的规则性的被积函数与潜在的大大提高的精度。预积分通常通过将$d$输入变量之一积分到函数中来完成。在高斯积分的常见情况下,也可以对变量的任何线性组合进行预积分。我们建议这样做,我们选择在一个积极的子空间分解的第一个特征向量是预集成的线性组合。我们发现,在数值例子中,这种主动子空间预集成策略是有竞争力的预集成的第一个变量的主成分构造的亚洲选项,其中主成分是已知的是非常有效的。它优于其他预集成方法对一些篮子选项,没有很好地建立默认。我们从理论上证明,就像在蒙特卡罗中一样,当使用加扰净积分时,预积分可以减少但不会增加方差。我们发现,在一个积极的子空间分解的领导特征向量是密切相关的向量,最大化一个不太容易处理的标准使用Sobol'指数找到最重要的线性组合的高斯变量。它们优化了涉及梯度的类似期望。我们表明,Sobol指数标准的领导特征向量是不变的方式,一个选择其余的$d-1$特征向量与高斯向量的采样。

英文摘要:

Pre-integration is an extension of conditional Monte Carlo to quasi-Monte Carlo and randomized quasi-Monte Carlo. It can reduce but not increase the variance in Monte Carlo. For quasi-Monte Carlo it can bring about improved regularity of the integrand with potentially greatly improved accuracy. Pre-integration is ordinarily done by integrating out one of $d$ input variables to a function. In the common case of a Gaussian integral one can also pre-integrate over any linear combination of variables. We propose to do that and we choose the first eigenvector in an active subspace decomposition to be the pre-integrated linear combination. We find in numerical examples that this active subspace pre-integration strategy is competitive with pre-integrating the first variable in the principal components construction on the Asian option where principal components are known to be very effective. It outperforms other pre-integration methods on some basket options where there is no well established default. We show theoretically that, just as in Monte Carlo, pre-integration can reduce but not increase the variance when one uses scrambled net integration. We show that the lead eigenvector in an active subspace decomposition is closely related to the vector that maximizes a less computationally tractable criterion using a Sobol' index to find the most important linear combination of Gaussian variables. They optimize similar expectations involving the gradient. We show that the Sobol' index criterion for the leading eigenvector is invariant to the way that one chooses the remaining $d-1$ eigenvectors with which to sample the Gaussian vector.

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