Conjugate gradient method is an iterative method, it applies to sparse matrix systems, because these systems such as the Cholesky decomposition of the direct method is too high.

• 共轭梯度法是一个迭代方法，所以它适用于稀疏矩阵系统，因为这些系统对于象乔莱斯基分解这样的直接方法太大了。