Thanks I solve it with
I have a exact solution of "cos(6*Pi*x)*cos(6*Pi*y)", so i can obtain the absolute error. the order of error from Armadillo is "-14", while Eigen's error has an order of "1". I also tried other methods "fullPivLu()", "householderQr()", the situation doesn't change.
But if i compute the relative error with Eigen's " double relative_error = (A*x - b).norm() / b.norm()", the relative_error is very small. I am confused by this situations.
On 9/8/2020 07:18，Adrien Escande<[email protected]> wrote：
Hi there,could you be more precise: how did you try to solve your problem with Eigen? How do you know/check that the problem is not solved correctly ?Best regards,Adrien EscandeOn Tue, Sep 8, 2020 at 12:55 AM ztdepyahoo <[email protected]> wrote:Dear sir:The matrix is generated from the spectral method of a simple heat diffusion problems, the dimension is 841.Attachment please find the a and rhs output from Armadillo.I am wandering why eigen's dense linear sover cann't solve it correctly.Regards
