Issue with rotational periodic BC

[martinkosch]

Hi and thank you for the good work!

I am trying to import a mesh that represents a slice of the full circular geometry of the simulated object. Therefore, I make use of rotational periodic boundary conditions. Reduced to a very minimal example in 2D, the mesh looks like this:

When importing this mesh with GmshDiscreteModel(), I run into the following issue:

ERROR: This line of code cannot be reached
Stacktrace:
 [1] error(s::String)
   @ Base ./error.jl:35
 [2] macro expansion
   @ ~/.julia/packages/Gridap/dKMpW/src/Helpers/Macros.jl:47 [inlined]
 [3] _setup_nodes_and_vertices_periodic(gmsh::Module, dimTags::Vector{Tuple{Int32, Int32}}, nnodes::Int64)
   @ GridapGmsh ~/.julia/packages/GridapGmsh/AdYVp/src/GmshDiscreteModels.jl:69
 [4] _setup_nodes_and_vertices(gmsh::Module, node_to_coords::Vector{VectorValue{2, Float64}})
   @ GridapGmsh ~/.julia/packages/GridapGmsh/AdYVp/src/GmshDiscreteModels.jl:42
 [5] GmshDiscreteModel(gmsh::Module)
   @ GridapGmsh ~/.julia/packages/GridapGmsh/AdYVp/src/GmshDiscreteModels.jl:29
 [6] GmshDiscreteModel(mshfile::String; renumber::Bool)
   @ GridapGmsh ~/.julia/packages/GridapGmsh/AdYVp/src/GmshDiscreteModels.jl:19
 [7] GmshDiscreteModel(mshfile::String)
   @ GridapGmsh ~/.julia/packages/GridapGmsh/AdYVp/src/GmshDiscreteModels.jl:6

It seems as if this error occurs because the node at Point 1 is linked to itself instead of another node. Is this kind of geometry generally not supported/possible or this there something wrong in my code or the package?

The .geo file:

SetFactory("OpenCASCADE");

// Parameters
r2 = 0.2; // Radius of the outer circle
slice_angle = 2*Pi/180 * 2; 

// Define the medium points and lines
Point(1) = {0, 0, 0};
Point(2) = {r2, 0, 0};
Line(1) = {1, 2};

// Rotational extrusion of as small slice
Extrude { {0, 0, 1}, {0, 0, 0}, slice_angle} {
Line{1}; Layers{0}; Recombine;
}

// Add periodic line
Periodic Line{3} = {1} Rotate { {0, 0, 1}, {0, 0, 0}, slice_angle};

// Labeling
Physical Line("BoundaryR2") = {2};
Physical Surface("InnerVol") = {1};

The .msh file:

$MeshFormat
4.1 0 8
$EndMeshFormat
$PhysicalNames
2
1 1 "BoundaryR2"
2 2 "InnerVol"
$EndPhysicalNames
$Entities
3 3 1 0
1 0 0 0 0 
2 0.2 0 0 0 
3 0.1995128100519649 0.01395129474882506 0 0 
1 -1.000000000028756e-07 -1e-07 -1e-07 0.2000001 1e-07 1e-07 0 2 1 -2 
2 0.1995127100519649 -1.000000000002735e-07 -1e-07 0.2000001 0.01395139474882506 1e-07 1 1 2 2 -3 
3 -1.000000000028756e-07 -1.000000000002735e-07 -1e-07 0.1995129100519649 0.01395139474882506 1e-07 0 2 1 -3 
1 -1.000000000028756e-07 -1.000000000002735e-07 -1e-07 0.2000001 0.01395139474882506 1e-07 1 2 3 -2 -1 3 
$EndEntities
$Nodes
7 5 1 5
0 1 0 1
1
0 0 0
0 2 0 1
2
0.2 0 0
0 3 0 1
3
0.1995128100519649 0.01395129474882506 0
1 1 0 1
4
0.09999999999999978 0 0
1 2 0 0
1 3 0 1
5
0.09975640502598221 0.006975647374412516 0
2 1 0 0
$EndNodes
$Elements
2 4 1 4
1 2 1 1
1 2 3 
2 1 2 3
2 3 2 5 
3 5 2 4 
4 4 1 5 
$EndElements
$Periodic
2
0 3 2
16 0.9975640502598242 -0.0697564737441253 0 0 0.0697564737441253 0.9975640502598242 0 0 0 0 1 0 0 0 0 1
1
3 2
1 3 1
16 0.9975640502598242 -0.0697564737441253 0 0 0.0697564737441253 0.9975640502598242 0 0 0 0 1 0 0 0 0 1
3
1 1
3 2
5 4
$EndPeriodic