def hat_function_collection(vertex_colors, color, element=None):
"""Return Expression on given element which takes values:
1 ... if vertex_colors[node] == color
0 ... at other nodes
This is well defined just on Lagrange 1 element (default) and Dicontinuous
Lagrange 1 element.
NOTE: This expression provides a little hack as it lacks continuity across
MPI partitions boundaries unless vertex_colors is compatible there. In fact,
this behaviour is needed in FluxReconstructor."""
assert isinstance(vertex_colors, cpp.VertexFunctionSizet)
mesh = vertex_colors.mesh()
if not element:
element = FiniteElement('Lagrange', mesh.ufl_cell(), 1)
assert element.family() in ['Lagrange', 'Discontinuous Lagrange']
assert element.degree() == 1
ufc_element, ufc_dofmap = jit(element, mpi_comm=mesh.mpi_comm())
dolfin_element = cpp.FiniteElement(ufc_element)
e = Expression(hats_cpp_code, element=element, domain=mesh)
e.vertex_colors = vertex_colors
e.color = color
e.dolfin_element = dolfin_element
return e
def hat_function(vertex):
"""Return Expression on Lagrange degree 1 element which is
1 ... at given 'vertex'
0 ... at other vertices
"""
assert isinstance(vertex, Vertex)
mesh = vertex.mesh()
element = FiniteElement('Lagrange', mesh.ufl_cell(), 1)
ufc_element, ufc_dofmap = jit(element, mpi_comm=mesh.mpi_comm())
ufc_element = make_ufc_finite_element(ufc_element)
dolfin_element = cpp.FiniteElement(ufc_element)
e = Expression(hat_cpp_code, element=element, domain=mesh)
e.vertex = vertex
e.dolfin_element = dolfin_element
return e
