I would strongly recommend not using mshr, as it is no longer maintained. The most common mesh generator to use is gmsh, which can be loaded with meshio as described in Transitioning from mesh.xml to mesh.xdmf, from dolfin-convert to meshio.
I would strongly recommend not using mshr, as it is no longer maintained. The most common mesh generator to use is gmsh, which can be loaded with meshio as described in Transitioning from mesh.xml to mesh.xdmf, from dolfin-convert to meshio.