BICGSTAB不收敛的坑！！

呜呜呜，我咋能遇到这么多坑！

A has large complex eigenpairs，BiCGSTAB is likely to stagnate, as confirmed by numerical experiments.

就是如果矩阵有很多复数特征值，BICGSTAB可能迭代不动了.

One may expect that higher-degree minimum residual polynomials may better handle this situation. This gives rise to algorithms including BiCGSTAB2^[1] and the more general BiCGSTAB(l)^[2]. In BiCGSTAB(l), a GMRES(l) step follows every l BiCG steps. BiCGSTAB2 is equivalent to BiCGSTAB(l) with l = 2.

还好转移张量是正定的，都是实数根嘿嘿，不会影响我实验