Throw error if no elements found in the model

[fredrikekre]

If there are no elements found in the model a very non-descriptive error is thrown. This can happen if you e.g. have a D-dimensional mesh, and add some physical groups for D-1 dimension, but none for D.

[koehlerson]

that's weird since
https://github.com/Ferrite-FEM/FerriteGmsh.jl/pull/16/files#diff-9bbe337b49a8f3ed93419ee748bd1cabb01e589a0fea7bce2492c780eb87a551R75
calls always with tag=-1 to get all elements with dim

help?> gmsh.model.mesh.getElements
  gmsh.model.mesh.getElements(dim = -1, tag = -1)

  Get the elements classified on the entity of dimension dim and tag tag. If tag < 0, get the elements for all entities of dimension dim.

can you post or send an example mesh file?

[fredrikekre]

Yea, I was also surprised about that, but

using FerriteGmsh: gmsh, saved_file_to_grid

# Initialize gmsh
gmsh.initialize()

# Add points
p1 = gmsh.model.geo.add_point(0.0, 0.0, 0.0)
p2 = gmsh.model.geo.add_point(1.0, 0.0, 0.0)
p3 = gmsh.model.geo.add_point(1.0, 1.0, 0.0)
p4 = gmsh.model.geo.add_point(0.0, 1.0, 0.0)

# Add the lines
l1 = gmsh.model.geo.add_line(p1, p2)
l2 = gmsh.model.geo.add_line(p2, p3)
l3 = gmsh.model.geo.add_line(p3, p4)
l4 = gmsh.model.geo.add_line(p4, p1)

# Create the closed curve loop
loop = gmsh.model.geo.add_curve_loop([l1, l2, l3, l4])

# Create the surface
surf = gmsh.model.geo.add_plane_surface([loop])

# Synchronize the model
gmsh.model.geo.synchronize()

# Create the physical domains
gmsh.model.addPhysicalGroup(1, [l1], -1, "1")
gmsh.model.addPhysicalGroup(1, [l2], -1, "2")
gmsh.model.addPhysicalGroup(1, [l3], -1, "3")
gmsh.model.addPhysicalGroup(1, [l4], -1, "4")
# gmsh.model.addPhysicalGroup(2, [surf])

# Synchronize the model
gmsh.model.geo.synchronize()

# Generate a 2D mesh
gmsh.model.mesh.generate(2)

# Save the mesh
gmsh.write("test.msh")

# Read the mesh
grid = saved_file_to_grid("test.msh")

errors without the gmsh.model.addPhysicalGroup(2, [surf]).

[fredrikekre]

https://stackoverflow.com/a/64428785/5087136 gave me the hint to add also a physical entity for 2D.