马尔科夫链
http://wenku.baidu.com/link?url=26MSlOhtBMPQJz3ta2p3bM6IMdLsvvHQ2mzw8AI2GcSdZAI7Ukdf1rl4KR6VUojnuutXwU5EqHNv-V0acHQn1PlkoyYT0j7DrVRWskg_Kr7&pn=50
蒙特卡洛采样算法
http://cos.name/2013/01/lda-math-mcmc-and-gibbs-sampling/
http://imbinwang.github.io/blog/mcmc-and-gibbs-sampling