expm(X) = V*diag(exp(diag(D)))/V
scaling expm using eigenvalue https://math.stackexchange.com/questions/3480626/eigenvalues-eigenvectors-of-scaled-matrix
标签：eigenvectors,eigenvalue,expm,diag,solving,https From： https://www.cnblogs.com/uceec00/p/17778462.html