抛物线法是求无约束一维极值的一种方法，也叫二次插值法，其理论依据为二次多项式可以在最优点附近较好的逼近函数的形状，做法是在函数的最优点附近取三个构造点，然后用这三个点构造一条抛物线，把这条抛物线的极值点作为函数的极值点的近似(The parabola is a method of solving a constrained one-dimensional extremum method, also called two times interpolation method, the theoretical basis for the two degree polynomial can be near the merit in the better approximation function of shape, is three points in the vicinity of the advantages of structure function, and then use these three points to construct a parabola. The extreme point of the parabola as the extreme points of function approximation.)