I am working on sub-function assignment. To facilitate caching of dof
indices for a particular assignment combination I suggest introducing a
FunctionAssigner class which caches the necessary indices (dofs) for the
whole domain.
Something like:
mesh = UnitSquareMesh(10,10)
V = FunctionSpace(mesh, "CG", 1)
VV = V*V
# Assign two scalar functions to the components of a mixed function
assigner0 = FunctionAssigner([V, V], VV)
# Assign components of a mixed function to scalar Functions
assigner1 = FunctionAssigner(VV, [V, V])
# Assign a scalar function to a component of a mixed function
assigner2 = FunctionAssigner(V, VV.sub(1))
u0, u1 = Function(V), Function(V)
U = Function(VV)
Then in some time loop:
while t < tstop:
...
assigner0.assign([u0, u1], U)
...
assigner1.assign(U, [u0, u1])
...
assigner2.assign(u0, U.sub(1))
In C++ the equivalent to a list of Foo will be a std::vector of shared Foos.
Comments?
By using sub spaces and sub functions we avoid using indices in the
interface, which I think is neat. However, there are some limitations with
the present interface:
1) The FunctionAssigner needs to have access to the local ownership range
of a sub dofmap, but that is not possible as it is set to 0,0 during
construction. Could we add a proper local ownership range to a sub dofmap?
2) The FunctionAssigner need to be able to access the private _vector of a
parent Function during the assignment, as calling subfunc.vector() raises
an error. This can be fixed by a friend statement. Is that acceptable?
Johan
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