Different behaviour of a mesh coming from generate_mesh() resp. UnitSquareMesh()?

[dokken]

Gmsh creates triangles and tetrahedrons by default. Using recombine, see: Files · master · gmsh / gmsh · GitLab

@EvaAnton

I use the create_mesh function presented here. Is there any way I can get the mesh node coordinates?

The create mesh function is part of dolfinx not dolfin.

@EvaAnton

Why do we need two xdmf filesL the triangle and the facet (cell type=lines)?

One is to save the mesh, while the other one is saving the facet data. To read it into dolfin, these needs to be separate.

@EvaAnton

It is not clear to me how I can read the mesh and use the markers I made in gmsh in order to add boundary conditions. Later, I will need to add a sudbomain in my mesh and problem, so I think that will answer my future question too.

You can load it in the same way as you load in mesh data. See for instance: Transitioning from mesh.xml to mesh.xdmf, from dolfin-convert to meshio - #3 by dokken