梯度下降法
https://www.jianshu.com/p/c7e642877b0e
牛顿法
https://blog.csdn.net/sigai_csdn/article/details/80678812
https://blog.csdn.net/ccnt_2012/article/details/81837154
综合比较
https://www.cnblogs.com/shixiangwan/p/7532830.html
