Fix coarsen DM

firedrake/mg/ufl_utils.py

@@ -268,20 +268,23 @@ def coarsen_snescontext(context, self, coefficient_mapping=None):
     coarse._fine = context
     context._coarse = coarse
 
-    # Now that we have the coarse snescontext, push it to the coarsened DMs
-    # Otherwise they won't have the right transfer manager when they are
-    # coarsened in turn
-    for val in chain(coefficient_mapping.values(), (bc.function_arg for bc in problem.bcs)):
-        if isinstance(val, (firedrake.Function, firedrake.Cofunction)):
-            V = val.function_space()
-            coarseneddm = V.dm
-            parentdm = get_parent(context._problem.u.function_space().dm)
-
-            # Now attach the hook to the parent DM
-            if get_appctx(coarseneddm) is None:
-                push_appctx(coarseneddm, coarse)
-                teardown = partial(pop_appctx, coarseneddm, coarse)
-                add_hook(parentdm, teardown=teardown)
+    solution = context._problem.u
+    solutiondm = solution.function_space().dm
+    parentdm = get_parent(solutiondm)
+    if parentdm != solutiondm:
+        # Now that we have the coarse snescontext, push it to the coarsened DMs
+        # Otherwise they won't have the right transfer manager when they are
+        # coarsened in turn
+        for val in chain(coefficient_mapping.values(), (bc.function_arg for bc in problem.bcs)):
+            if isinstance(val, (firedrake.Function, firedrake.Cofunction)):
+                V = val.function_space()
+                coarseneddm = V.dm
+
+                # Now attach the hook to the parent DM
+                if get_appctx(coarseneddm) is None:
+                    push_appctx(coarseneddm, coarse)
+                    teardown = partial(pop_appctx, coarseneddm, coarse)
+                    add_hook(parentdm, teardown=teardown)
 
     ises = problem.J.arguments()[0].function_space()._ises
     coarse._nullspace = self(context._nullspace, self, coefficient_mapping=coefficient_mapping)
@@ -384,7 +387,8 @@ def create_interpolation(dmc, dmf):
     mat.setType(mat.Type.PYTHON)
     mat.setPythonContext(ctx)
     mat.setUp()
-    return mat, None
+    rscale = mat.createVecLeft() if row_size == col_size else None
+    return mat, rscale
 
 
 def create_injection(dmc, dmf):