Dear Luca, That is some fascinating information! It seems like step-44, for instance, does not follow this recommendation, as there the polynomial degree is 2, while the quadrature degree is 3, instead of the recommended 5 ( https://dealii.org/developer/doxygen/deal.II/step_44.html#FiniteElementsystem). Is it because of the exception for squares you mentioned?
Do you have a reference that goes in depth on the topic of the choice of quadrature degrees? If so, I would grandly appreciate if you could send it my way. Incidentally, have you been able to give any thought on the singularity of the mass matrix, even with the quadrature order is high? Kind regards, Bob On Fri, 12 Apr 2019 at 16:26, luca.heltai <[email protected]> wrote: > If you plan to use any domain that is not a square (or an affine > transformation), you have to make sure you integrate exactly the product of > two polynomials of order degree and of the determinant of the Jacobian. > This last term is constant only for simple meshes, but it is the square > root of a polynomial of order (degree-1) in more complicated cases. > > 2*fe_degree is ok for most cases, but I would not use this for serious > calculations. I prefer to be on the safe side… > > :) > > L. > > > On 11 Apr 2019, at 19:34, Robert Spartus <[email protected]> wrote: > > > > Dear Luca, > > > > Thanks for your suggestion. Unfortunately, it did not solve the problem. > I am sending the modified version, as well as the output of the program. > > > > Out of curiosity, what is the reason to use (2*fe_degree + 1)? Checking > step-8, I notice that there a quadrature degree one larger than the > polynomial degree is also used. > > > > Bests, > > Bob > > > > -- > The deal.II project is located at http://www.dealii.org/ > For mailing list/forum options, see > https://groups.google.com/d/forum/dealii?hl=en > --- > You received this message because you are subscribed to the Google Groups > "deal.II User Group" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > For more options, visit https://groups.google.com/d/optout. > -- The deal.II project is located at http://www.dealii.org/ For mailing list/forum options, see https://groups.google.com/d/forum/dealii?hl=en --- You received this message because you are subscribed to the Google Groups "deal.II User Group" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
