It is well known that, for nonsingular systems where $A$ is invertible,the iterative method converges if and only if the spectral radius of the iteration matrix is strictly less than 1.

• 众所周知，对于非奇异的线性方程组，即该方程组的系数矩阵A是可逆的，此时求解该方程组的迭代法收敛的充分必要条件是迭代矩阵的谱半径严格小于1。