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arXiv 0908.2098stat.MEstat.CO
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几何漂移条件下MCMC的严格置信界

Rigorous confidence bounds for MCMC under a geometric drift condition

Krzysztof Latuszynski, Wojciech Niemiro

摘要:

我们假设一个漂移条件对一个小的集合和边界的平均值沿一个单一的轨迹的马尔可夫链蒙特卡罗算法的估计得到的均方误差。我们使用这些界限来构造固定宽度的非渐近置信区间。对于可能无界的函数$f:\stany \to R,$,令$I=\int_{\stany} f(x) π(x) dx$为目标值,$\hat{I}_{t,n}=(1/n)\sum_{i=t}^{t+n-1}f(X_i)$为其MCMC估计。准确地说,我们推导出轨迹$n$和老化时间$t$的长度的下限,其确保$$P(|\hat{I}_{t,n}-I|\leq \varepsilon)\geq 1-α.$$该界限仅明确地依赖于漂移参数,基于$f,$的$V-$范数,其中$V$是漂移函数,以及精度和置信度参数$\varepsilon, α.$接下来,我们分析基于多个较短运行的中位数的MCMC估计量,该估计量允许所需总数的更清晰界限仿真成本特别是该方法可以应用于计算贝叶斯估计在实际相关的模型。我们用一个简单的例子来说明我们的界限。

英文摘要:

We assume a drift condition towards a small set and bound the mean square error of estimators obtained by taking averages along a single trajectory of a Markov chain Monte Carlo algorithm. We use these bounds to construct fixed-width nonasymptotic confidence intervals. For a possibly unbounded function $f:\stany \to R,$ let $I=\int_{\stany} f(x) π(x) dx$ be the value of interest and $\hat{I}_{t,n}=(1/n)\sum_{i=t}^{t+n-1}f(X_i)$ its MCMC estimate. Precisely, we derive lower bounds for the length of the trajectory $n$ and burn-in time $t$ which ensure that $$P(|\hat{I}_{t,n}-I|\leq \varepsilon)\geq 1-α.$$ The bounds depend only and explicitly on drift parameters, on the $V-$norm of $f,$ where $V$ is the drift function and on precision and confidence parameters $\varepsilon, α.$ Next we analyse an MCMC estimator based on the median of multiple shorter runs that allows for sharper bounds for the required total simulation cost. In particular the methodology can be applied for computing Bayesian estimators in practically relevant models. We illustrate our bounds numerically in a simple example.

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