The last algorithm is also based on piecewise quadratic process, and the difference is in that the orthonormal matrix is constructed by two-step Arnoldi process.

• 最后给出的基于二重Arnoldi过程的分段二次化算法和QR-TPWQ算法一样，也是基于非线性函数多点Taylor展开的分段二次化方法的，唯一的不同是用来模型降阶的正交基由二重Arnoldi过程得出。