Hello Bruno and David, Thank you for the quick reply and the quick fix! I'll give it a try.
Cheers, Arthur Le mercredi 20 août 2025 à 16:11:58 UTC-4, Wells, David a écrit : > Hi Arthur, > > Thank you for reporting this! This is another simplex bug inside deal.II. > From 1999ish until 2021 we assumed 2d grids had consistently oriented > lines, but this cannot be enforced in for triangles in 2d, and over the > last two years I've been fixing a long tail of minor bugs related to this > assumption. I have a patch which fixes this here: > > https://github.com/dealii/dealii/pull/18832 > > I gave you credit for figuring this one out in the changelog. > > Best, > David Wells > ------------------------------ > *From:* [email protected] <[email protected]> on behalf of > [email protected] <[email protected]> > *Sent:* Wednesday, August 20, 2025 9:56 AM > *To:* deal.II User Group <[email protected]> > *Subject:* [deal.II] Re: Convergence issues for cubic FE_SimplexP on > triangles > > Dear Arthur, > Thank you for the very thorough and detailed question. I'll look into and > try to get back to you (or at least try to reach out to people that might > have a clearer idea). If that can reassure you, I have tried to reproduce > your results using Lethe and I get the same conclusion to you regarding > convergence of P3 triangles. > I'll look into it and ask around. Might take a small while, but I am on it > :) > > > > On Friday, August 15, 2025 at 6:45:17 p.m. UTC+2 [email protected] wrote: > > Good morning deal.ii developers, > > I was doing convergence tests with a manufactured solution with simplicial > meshes and did not obtain the expected convergence with cubic elements on > triangles (FE_SimplexP<2>(3)). I wrote a very simple interpolation > convergence test to check: on tetrahedra, all degrees converge with the > expected rates in L2, Linf and H1 (semi)norms; on triangles the results are > good for P1 and P2 on triangles, but not for P3, where I get first order > convergence for L2, Linf and no convergence in H1: > > P1 on triangles > Number of dofs: 25 > Number of dofs: 81 > Number of dofs: 289 > Number of dofs: 1089 > nElm L2_u Li_u H1_u > 32 5.938414e-03 - - 2.425255e-02 - - 1.549249e-01 - - > 128 1.498810e-03 3.96 1.99 6.769010e-03 3.58 1.84 7.782930e-02 1.99 0.99 > 512 3.755853e-04 3.99 2.00 1.780487e-03 3.80 1.93 3.896037e-02 2.00 1.00 > 2048 9.395142e-05 4.00 2.00 4.561509e-04 3.90 1.96 1.948590e-02 2.00 1.00 > > P2 on triangles > Number of dofs: 81 > Number of dofs: 289 > Number of dofs: 1089 > Number of dofs: 4225 > nElm L2_u Li_u H1_u > 32 3.112575e-04 - - 6.997055e-04 - - 1.041667e-02 - - > 128 3.890718e-05 8.00 3.00 8.746319e-05 8.00 3.00 2.604167e-03 4.00 2.00 > 512 4.863398e-06 8.00 3.00 1.093290e-05 8.00 3.00 6.510417e-04 4.00 2.00 > 2048 6.079247e-07 8.00 3.00 1.366612e-06 8.00 3.00 1.627604e-04 4.00 2.00 > > P3 on triangles > Number of dofs: 169 > Number of dofs: 625 > Number of dofs: 2401 > Number of dofs: 9409 > nElm L2_u Li_u H1_u > 32 1.541667e-02 - - 7.120958e-02 - - 5.117887e-01 - - > 128 8.815536e-03 1.75* 0.81* 4.355310e-02 1.64* 0.71* 5.712863e-01 0.90* > -0.16* > 512 4.690321e-03 1.88 *0.91* 2.389578e-02 1.82* 0.87* 6.001976e-01 0.95* > -0.07* > 2048 2.416438e-03 1.94 *0.96* 1.249422e-02 1.91 *0.94* 6.144240e-01 0.98* > -0.03* > > P1 on tets > Number of dofs: 125 > Number of dofs: 729 > Number of dofs: 4913 > Number of dofs: 35937 > nElm L2_u Li_u H1_u > > 384 8.095068e-03 - - 6.562605e-02 - - 1.735667e-01 - > - > 3072 2.289416e-03 3.54 1.82 2.693394e-02 2.44 1.28 9.615581e-02 1.81 > 0.85 > 24576 5.896877e-04 3.88 1.96 7.780330e-03 3.46 1.79 4.927053e-02 1.95 > 0.96 > 196608 1.485159e-04 3.97 1.99 2.081313e-03 3.74 1.90 2.478494e-02 1.99 > 0.99 > > P2 on tets > Number of dofs: 729 > Number of dofs: 4913 > Number of dofs: 35937 > Number of dofs: 274625 > nElm L2_u Li_u H1_u > > 384 1.118739e-03 - - 1.184543e-02 - - 2.361912e-02 - > - > 3072 1.637572e-04 6.83 2.77 3.376606e-03 3.51 1.81 6.731956e-03 3.51 > 1.81 > 24576 2.117353e-05 7.73 2.95 4.535571e-04 7.44 2.90 1.732030e-03 3.89 > 1.96 > 196608 2.668408e-06 7.93 2.99 5.866221e-05 7.73 2.95 4.360374e-04 3.97 > 1.99 > > P3 on tets > Number of dofs: 2197 > Number of dofs: 15625 > Number of dofs: 117649 > Number of dofs: 912673 > nElm L2_u Li_u H1_u > > 384 1.074553e-04 - - 7.422949e-04 - - 2.346755e-03 - > - > 3072 8.111057e-06 13.25 *3.73* 1.300853e-04 5.71 *2.51* 3.362943e-04 > 6.98* 2.80* > 24576 5.264880e-07 15.41 *3.95* 8.130328e-06 16.00 *4.00* 4.327503e-05 > 7.77 *2.96* > 196608 3.320390e-08 15.86 *3.99* 5.081455e-07 16.00 *4.00* 5.447386e-06 > 7.94 > * 2.99 * > > Is there something that I'm doing wrong, or is it just a bug somewhere in > FE_SimplexP? > I have joined a MWE with the 2D and 3D meshes (in .msh4 format). > > Thank you for your help, and thanks a lot for developing the library! > Arthur Bawin > > -- > 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]. > To view this discussion visit > https://groups.google.com/d/msgid/dealii/2d16fa24-b5f7-4ddd-9714-19da192846bcn%40googlegroups.com > > <https://groups.google.com/d/msgid/dealii/2d16fa24-b5f7-4ddd-9714-19da192846bcn%40googlegroups.com?utm_medium=email&utm_source=footer> > . > -- 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. 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