C的正定矩阵计算，主要用于求解对称正定方程组的平方根，利用的是乔里斯基分解法求解系数矩阵为对称正定。-C positive definite matrix calculation, mainly used to solve the equations of symmetric positive definite square root, and use of the Cholesky decomposition method for solving the coefficient matrix is ​ ​ symmetric positive definite.