On Mon, Sep 25, 2023 at 8:58 AM Azeddine Messikh via petsc-users < [email protected]> wrote:
> Dear developers > > I tried to run ex24.c > https://petsc.org/release/src/snes/tutorials/ex24.c.html using the > following command line > > ./ex24 -sol_type quadratic -dm_plex_simplex 0 -field_petscspace_degree 1 > -potential_petscspace_degree 1 -dm_plex_box_faces 2,1 > > I discovered that at > > 254: PetscCall > <https://petsc.org/release/manualpages/Sys/PetscCall/>(PetscWeakFormSetIndexBdResidual(wf, > label, 1, 0, 0, 0, f0_bd_quadratic_q, 0, NULL)); > > reverses the value of the integrals at the top only. That is > The boundary integral corresponding to node 5 becomes that of 4 and > vise-versa. > Same thing for nodes 5 and 6. > I apologize for taking so long to reply. This email fell out of my Inbox. I believe the problem is understanding the ordering of unknowns in Plex. For all shapes, I orient the boundary to have outward normals. This means that for quads, the vertex ordering would be 1--2--5--4 and 2--3--6--5 Does this make sense? Thanks, Matt > The mesh index is as follows > *4---*5---*6 > | | | > | | | > *1--- *2---*3 > > However, if I use -dm_plex_simplex 1 there is no problem. > > The model is in the form Au = b > > the value of b with "-dm_plex_simplex 0" is > [0.25 > 0.0104167 > 0. > 0. > 0.145833 > 0. > -0.583333 > 0.177083 > 0. > 0.0833333 > -0.28125 > 0. > 0. > -0.6875 > 0. > -0.75 > -0.364583 > 0.] > > and for -dm_plex_simplex 1 > [0.0833333 > 0.0104167 > 0. > 0. > 0.145833 > 0. > -0.583333 > 0.177083 > 0. > 0.25 > -0.260417 > 0. > 1.43404e-16 > -0.645833 > 0. > -0.75 > -0.427083 > 0.] > > you can see that the value at node 1 =0.25 and node 4 = 0.0833333 ( > simplex 0) > which is reversed, that is, node 4 =0.25 and node 1 = 0.0833333 > (simplex 1) > > So, my own calculation shows that at node 1 should be 0.083333 not 0.25. > The -dm_plex_simplex 1 gives the correct answer but -dm_plex_simplex 0 > gives wrong answer. > > > Would you please help me in this matter. > Sincerely yours > Azeddine M > > > > > > > > -- What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead. -- Norbert Wiener https://www.cse.buffalo.edu/~knepley/ <http://www.cse.buffalo.edu/~knepley/>
