中文说明：FR共轭梯度算法求极小值。y为给定函数，x为函数变量，x0为搜索起始点返回值fm为极小值，xm为极小值点
English Description：
FR Conjugate gradient algorithm is used to find the minimum. Y is the given function, X is the function variable, x0 is the search starting point, FM is the minimum value, XM is the minimum point