Hello everyone,

I will appreciate it if anyone can help me to understand what is the problem.

I am reading a mesh like this.

I can read the mesh and select the boundaries and I can get physical groups.

I used this function to create subdomains and boundaries:

```
def make2Dmesh(msh):
triangle_mesh = create_mesh(msh, "triangle", prune_z=True)
meshio.write(os.path.join(main_path, "Mesh/mesh.xdmf"), triangle_mesh)
triangle_mesh = create_mesh(msh, "triangle", prune_z=True)
meshio.write(os.path.join(main_path, "Mesh/cf.xdmf"), triangle_mesh)
line_mesh = create_mesh(msh, "line", prune_z=True)
meshio.write(os.path.join(main_path, "Mesh/mf.xdmf"), line_mesh)
inmesh = Mesh(MPI.comm_self)#Mesh()
# Mesh information
with XDMFFile(MPI.comm_self, os.path.join(main_path, 'Mesh/mesh.xdmf')) as f:
f.read(inmesh)
# Boundary line information
mvc = MeshValueCollection("size_t", inmesh, 1)
with XDMFFile(MPI.comm_self, os.path.join(main_path, 'Mesh/mf.xdmf')) as f_ph:
f_ph.read(mvc, 'name_to_read')
boundaries = MeshFunctionSizet(inmesh, mvc)
# Material information
mvc2 = MeshValueCollection("size_t", inmesh, inmesh.geometric_dimension())
with XDMFFile(MPI.comm_self, os.path.join(main_path, 'Mesh/cf.xdmf')) as f_ph:
f_ph.read(mvc2, 'name_to_read')
materials = MeshFunctionSizet(inmesh, mvc2)
return inmesh, materials, boundaries
```

The problem that I encountered is that when I use:

```
dx = Measure('dx', domain=msh, subdomain_data=materials)
ds = Measure('ds', domain=msh, subdomain_data=boundaries)
```

I have all information regarding “dx” but “ds” only has value on the exterior boundary curve.

I used this to check the values:

```
for i in range(20):
if boundaries.where_equal(i):
print(f"boundary: {i}")
print("Circumference is: ", assemble(Constant(1) * ds(i)))
for i in range(20):
if materials.where_equal(i):
print(f"subdomain: {i}")
print("Area is: ", assemble(10*dx(I)))
```

and the output is:

```
boundary: 8
Circumference is: 0.0
boundary: 9
Circumference is: 0.0
boundary: 10
Circumference is: 0.0
boundary: 11
Circumference is: 0.4083935358272394
****************************************
subdomain: 12
Area is: 0.0031358538980296065
subdomain: 13
Area is: 0.047112009142460345
subdomain: 14
Area is: 0.013351739776037257
subdomain: 15
Area is: 0.0691151254391912
```

Thank you in advance.