I don't think you were harsh nor did take it that way. That was very
considerate of you nonetheless.
It was a light sleezy comment on my end. I should be more careful.
Thanks again.
On Wednesday, January 11, 2023 at 3:47:52 PM UTC+2 luca....@gmail.com wrote:
> I didn’t mean to sound too harsh, sorry for that. I could spot the mistake
> right away because it is a mistake I do all the time.
>
> No embarrassment is needed, and no question is ever a stupid question.
> Don’t worry! I’ve been in your shoes so many times I cannot count them
> anymore…
>
> :)
>
> Luca.
>
> > On 11 Jan 2023, at 14:33, Abbas <abbas.b...@gmail.com> wrote:
> >
> > Well, this is embarrassing.
> > Thank you very much
> >
> > On Wednesday, January 11, 2023 at 3:11:11 PM UTC+2 luca....@gmail.com
> wrote:
> > You have an issue in your boundary worker.
> >
> >
> > The boundary worker is called passing a cell, a face_no, scratch, and
> copy. Yet, in your code, you loop again on the faces of the cell:
> >
> >
> > for (const auto &face : cell->face_iterators())
> > {
> > if ( ((face->boundary_id() == 0) || (face->boundary_id() == 1)))
> >
> >
> > this should become
> >
> > if((cell->face(face_no)->boundary_id() == 0) ||
> (cell->face(face_no)->boundary_id() == 1) {
> >
> > …
> >
> > }
> >
> > otherwise, you are going to assemble the face terms twice on the four
> corners.
> >
> > Best,
> > Luca.
> >
> > > On 11 Jan 2023, at 12:05, Abbas <abbas.b...@gmail.com> wrote:
> > >
> > > Hello,
> > >
> > > Setting:
> > > 1) Unit square domain,
> > > 2) Simple scalar Laplacian with no source term.
> > > 3) 0 and 1 Dirichlet on opposite ends of the square and zero Neumann
> on the other two edges.
> > >
> > > I am trying to solve the above problem using SIPG by adopting step 74.
> The expected solution should be perfectly linear with a constant gradient
> as the problem reduces to a pseudo 1-D problem.
> > >
> > > That is the case if I use CG, but with DG I do not get a perfectly
> linear solution and that is causing me problems.
> > >
> > > I have attached below a single image file that includes:
> > > 1) The solution.
> > > 2) The solution gradient with weird behaviour at the corners
> > > 3) Line plot of the solution across the lower wall.
> > >
> > > and the code I am using which is based on step 74.
> > >
> > > Things I tried/looked into:
> > > - I tried to adapt the code to CG and I get the expected results. I
> can't straight up impose BCs strongly with DG here.
> > > - I am sure this isn't a Paraview issue because I tried integrating
> across the boundary within deal and I am getting mesh dependent results.
> > > - The weak form is correct. The Neuman BC shows up as a boundary
> integral in the rhs which has no contribution. (Neumann zero at these
> walls).
> > > - I looked into the distributed LDG method within the dealii gallary
> and adopted it to these BCs and I didn't have this problem.
> > >
> > > The only thing I haven't tried yet is to do a simple problem by hand
> and compare the dealii and my outputs. Before doing that, any ideas on how
> I can debug this? Is this something associated with imposing BCs weakly
> with SIPG and will happen no matter what?
> > >
> > > best,
> > > Abbas
> > >
> > >
> > >
> > > --
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>
>
> > > <Screenshot from 2023-01-11 12-39-11.png><SIPG.cc>
> >
> >
> > --
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>
>
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