Losing subdomain after dolfin.refine()

General
1

Hello,

It appears that after using dolfin.refine(), my mesh loses its subdomain info, is there anyway to preserve that or at least re-define the subdomain? My example code is shown below, as well as the original mesh with subdomain and the new mesh losing subdomain.
mesh1mesh2

import numpy as np
from dolfin import *
from mshr import *
import matplotlib.pyplot as plt

domain = Rectangle(Point(0., 0.), Point(1., 1.))
domain.set_subdomain(1, Rectangle(Point(0.1,0.1), Point(0.6, .6)))
resolution=10
mesh = generate_mesh(domain, resolution)
mf = MeshFunction("size_t", mesh, 2, mesh.domains())

plt.figure()
plot(mesh,linewidth=0.5)
plot(mf)
plt.savefig('mesh1.png')
plt.show()


cell_markers = MeshFunction("bool", mesh, dim=2)
cell_markers.set_all(False)
for cell in cells(mesh):
    p = cell.midpoint()
    if p[1] > 0.5:
        cell_markers[cell] = True
mesh2 = refine(mesh, cell_markers)
mf2 = MeshFunction("size_t", mesh2, 2, mesh2.domains())

plt.figure()
plot(mesh2,linewidth=0.5)
plot(mf2)
plt.savefig('mesh2.png')
plt.show()
2

You need to call the adapt-command as for instance done for facet markers here Adapt for mesh and MeshFunctions - #2 by dokken