共轭梯度法计算线性方程组的代码。本段代码采用了F90的风格书写。注意共轭梯度法只适用于对称正定的矩阵。-Conjugate gradient method to calculate the linear equations of the code. The section of code uses the the F90 style of writing. Note conjugate gradient method is only applicable to symmetric positive definite matrix.