使用特征库在C ++中计算多项式的根

Question

如何使用特征库在C ++中获得具有系数的多项式的根？

在Python中：

>>> import numpy as np
>>> coeff = [0.708563939215852, -0.3111717537041549, -0.2151830138973625]
>>> np.roots(coeff)
array([ 0.81279407, -0.37363574])

在Matlab中：

>> coeff = [0.708563939215852, -0.3111717537041549, -0.2151830138973625]
>> roots(coeff)
ans = 
   0.812794068532020
   -0.373635742116877

我在C ++中使用Eigen Library进行了尝试，但收到了不同的结果：

#include <unsupported/Eigen/Polynomials>

Eigen::Vector3d coeff(0.708563939215852, -0.3111717537041549, -0.2151830138973625);
Eigen::PolynomialSolver<double, Eigen::Dynamic> solver;
solver.compute(coeff);
const Eigen::PolynomialSolver<double, Eigen::Dynamic>::RootsType &r = solver.roots();

--> r[2] = {{1.2303239390096565, 0.000}, {-2.6764034787849331, 0.000}}

Answer 1

感谢@ rafix07的注释，以下代码为我提供了与NumPy和MATLAB中相同的结果。系数的顺序必须交换。

#include <unsupported/Eigen/Polynomials>

Eigen::Vector3d coeff(0.708563939215852, -0.3111717537041549, -0.2151830138973625);
Eigen::PolynomialSolver<double, Eigen::Dynamic> solver;
solver.compute(coeff);
const Eigen::PolynomialSolver<double, Eigen::Dynamic>::RootsType &r = solver.roots();