Apply Diriclet boundary on the Cofunction RHS.

firedrake/variational_solver.py

@@ -10,6 +10,7 @@
     DEFAULT_SNES_PARAMETERS
 )
 from firedrake.function import Function
+from firedrake.cofunction import Cofunction
 from firedrake.functionspace import RestrictedFunctionSpace
 from firedrake.ufl_expr import TrialFunction, TestFunction
 from firedrake.bcs import DirichletBC, EquationBC
@@ -305,6 +306,10 @@ def solve(self, bounds=None):
 
         for dbc in problem.dirichlet_bcs():
             dbc.apply(problem.u_restrict)
+            for coeff in coefficients:
+                if isinstance(coeff, Cofunction):
+                    # Apply the DirichletBC to the right hand side of the equation.
+                    dbc.apply(coeff)
 
         if bounds is not None:
             lower, upper = bounds

tests/regression/test_cofunction.py

@@ -60,3 +60,43 @@ def test_scalar_cofunction_zero_with_subset(V):
     assert f is g
     assert np.allclose(f.dat.data_ro[:2], 0.0)
     assert np.allclose(f.dat.data_ro[2:], 1.0)
+
+
+def test_diriclet_bc_rhs(V):
+    # Issue https://github.com/firedrakeproject/firedrake/issues/3498
+    # Apply DirichletBC to RHS (Cofunction) in LinearVariationalSolver
+    mesh = UnitIntervalMesh(2)
+    space = FunctionSpace(mesh, "Lagrange", 1)
+    test, trial = TestFunction(space), TrialFunction(space)
+
+    # Form RHS
+    u = Function(space, name="u")
+    problem = LinearVariationalProblem(
+        inner(trial, test) * dx, inner(Constant(1.0), test) * dx, u,
+        DirichletBC(space, 0.0, "on_boundary"))
+    solver = LinearVariationalSolver(problem)
+    solver.solve()
+
+    assert np.allclose(assemble(inner(u, u) * ds), 0.0)
+
+    # Cofunction RHS
+    b = assemble(inner(Constant(1.0), test) * dx)
+    u = Function(space, name="u")
+    problem = LinearVariationalProblem(
+        inner(trial, test) * dx, b, u,
+        DirichletBC(space, 0.0, "on_boundary"))
+    solver = LinearVariationalSolver(problem)
+    solver.solve()
+
+    assert np.allclose(assemble(inner(u, u) * ds), 0.0)
+
+    # FormSum RHS
+    b = assemble(inner(Constant(0.5), test) * dx) + inner(Constant(0.5), test) * dx
+    u = Function(space, name="u")
+    problem = LinearVariationalProblem(
+        inner(trial, test) * dx, b, u,
+        DirichletBC(space, 0.0, "on_boundary"))
+    solver = LinearVariationalSolver(problem)
+    solver.solve()
+
+    assert np.allclose(assemble(inner(u, u) * ds), 0.0)