Detect the mat_type of assembled Jacobian

Author: pbrubeck

firedrake/variational_solver.py

@@ -234,6 +234,17 @@ def update_diffusivity(current_solution):
         assert isinstance(problem, NonlinearVariationalProblem)
 
         solver_parameters = flatten_parameters(solver_parameters or {})
+
+        if isinstance(problem.J, MatrixBase):
+            solver_parameters.setdefault("mat_type", problem.J.mat_type)
+            if solver_parameters["mat_type"] != problem.J.mat_type:
+                raise ValueError("Cannot change the mat_type of an already assembled matrix.")
+
+        if isinstance(problem.Jp, MatrixBase):
+            solver_parameters.setdefaul("pmat_type", problem.Jp.mat_type)
+            if solver_parameters["pmat_type"] != problem.Jp.mat_type:
+                raise ValueError("Cannot change the mat_type of an already assembled matrix.")
+
         solver_parameters = solving_utils.set_defaults(solver_parameters,
                                                        problem.J.arguments(),
                                                        ksp_defaults=self.DEFAULT_KSP_PARAMETERS,

tests/firedrake/regression/test_matrix_free.py

@@ -198,6 +198,7 @@ def test_fieldsplitting(mesh, preassembled, parameters, rhs):
         b = assemble(L)
         solve(A, f, b, solver_parameters=parameters)
     else:
+        parameters = parameters.copy()
         parameters["mat_type"] = "matfree"
         solve(a == L, f, solver_parameters=parameters)