http://www.360doc.com/content/18/0411/23/22669593_744877500.shtml
https://blog.csdn.net/sherrylml/article/details/53781163
http://www.math.wpi.edu/saspdf/iml/chap11.pdf
优化类的工作
原文：https://www.cnblogs.com/uceec00/p/12663911.html
