目标参数分布情况很复杂，我们想求相关的目标参数（f（x））很难，所以想通过MCMC从目标函数采取样本估计我们想要的结果，大致流程构造一条马尔可夫链去逼近目标函数，从其稳态装下抽取样本。(The distribution of target parameters is very complicated, and it is difficult for us to find the relevant target parameters (f (x)), so we want to use MCMC to take samples from the target function to estimate the results we want, and construct a markov chain to approximate the target function and extract samples from its steady-state assembly.)