How can one integrate over the single facet marked with 2 in the xml marked mesh defined below?
<?xml version="1.0"?>
<dolfin xmlns:dolfin="http://fenicsproject.org">
<mesh celltype="triangle" dim="2">
<vertices size="4">
<vertex index="0" x="0.000000000000000e+00" y="0.000000000000000e+00" />
<vertex index="1" x="1.000000000000000e+00" y="0.000000000000000e+00" />
<vertex index="2" x="0.000000000000000e+00" y="1.000000000000000e+00" />
<vertex index="3" x="1.000000000000000e+00" y="1.000000000000000e+00" />
</vertices>
<cells size="2">
<triangle index="0" v0="0" v1="1" v2="3" />
<triangle index="1" v0="0" v1="2" v2="3" />
</cells>
<domains>
<mesh_value_collection name="f" type="uint" dim="1" size="6">
<value cell_index="0" local_entity="0" value="0" />
<value cell_index="0" local_entity="1" value="0" />
<value cell_index="0" local_entity="2" value="0" />
<value cell_index="1" local_entity="0" value="0" />
<value cell_index="1" local_entity="1" value="0" />
<value cell_index="1" local_entity="2" value="2" />
</mesh_value_collection>
</domains>
</mesh>
</dolfin>
I would assume one could read the mesh function out of the file. I try this
mesh = Mesh("mesh.xml")
meshfunc = MeshFunction("size_t", mesh, "mesh.xml")
and get the error
*** -------------------------------------------------------------------------
*** Error: Unable to read DOLFIN XML data.
*** Reason: Unable to find tag <mesh_value_collection>.
*** Where: This error was encountered inside xmlutils.cpp.
*** Process: 0
*** DOLFIN version: 1.3.0
