Knook/EquationBC_GMG

[KarsKnook]

Necessary code to get geometric multigrid working with EquationBC.

MFE:

from firedrake import *

mesh = UnitIntervalMesh(10)
mesh_hierarchy = MeshHierarchy(mesh, 1)
mesh = mesh_hierarchy[-1]
x = SpatialCoordinate(mesh)

V = FunctionSpace(mesh, "CG", 1)
print(f"# DoFs = {V.dim()}")
u = Function(V)
v = TestFunction(V)

f = pi**2 * sin(pi * x[0])  # gives exact solution u = sin(pi*x)
F = (inner(grad(u), grad(v)) - inner(f, v)) * dx

bcs = [EquationBC(inner(u, v) * ds == 0, u, "on_boundary", V=V)]
#bcs = [DirichletBC(V, 0, "on_boundary")]

sp = {
    "snes_monitor": None,
    "ksp_monitor": None,
    #"pc_type": "lu",
    #"pc_factor_mat_solver_type": "mumps",
    "pc_type": "mg",
    "mg_coarse": {
        "ksp_monitor": None,
        "pc_type": "lu",
        "pc_factor_mat_solver_type": "mumps",
        },
    "mg_levels": {
        "ksp_monitor": None,
        "ksp_type": "richardson",
        "pc_type": "none",
        },
}

NLVP = NonlinearVariationalProblem(F, u, bcs=bcs)
NLVS = NonlinearVariationalSolver(NLVP, solver_parameters=sp)
NLVS.solve()

[connorjward]

If this is a bugfix this should likely go into release, not master. In particular notice the large number of extra commits that are erroneously included here.

Also if you have an MFE that this fixes then please include some sort of test.

[pbrubeck]

Line 286 ufl_utils.py should extract the Functions from the Form in EquationBC

[pbrubeck]

BCBase or EquationBC should implement zero()