Store local grid functions instead of global ones

After consulting Steffen

python/dune/perftool/pdelab/function.py

@@ -12,19 +12,6 @@ from dune.perftool.pdelab.localoperator import name_gridfunction_member
 import pymbolic.primitives as prim
 
 
-def local_gridfunction(coeff, restriction, diffOrder):
-    gf = name_gridfunction_member(coeff, diffOrder)
-    name = "{}_local".format(gf)
-    define_local_gridfunction(name, gf)
-    bind_gridfunction_to_element(name, restriction)
-    return name
-
-
-@preamble
-def define_local_gridfunction(name, gf):
-    return "auto {} = localFunction({});".format(name, gf)
-
-
 @preamble
 def bind_gridfunction_to_element(gf, restriction):
     element = name_cell(restriction)
@@ -42,7 +29,8 @@ def declare_grid_function_range(gridfunction):
 def pymbolic_evaluate_gridfunction(name, coeff, restriction, grad):
     diffOrder = 1 if grad else 0
 
-    gridfunction = local_gridfunction(coeff, restriction, diffOrder)
+    gridfunction = name_gridfunction_member(coeff, diffOrder)
+    bind_gridfunction_to_element(gridfunction, restriction)
 
     temporary_variable(name,
                        shape=(1,) + (world_dimension(),) * diffOrder,

python/dune/perftool/pdelab/localoperator.py

@@ -158,7 +158,7 @@ def localoperator_basename(form_ident):
 
 
 def name_gridfunction_member(coeff, diffOrder=0):
-    name = "gridfunction_coeff{}_diff{}".format(coeff.count(), diffOrder)
+    name = "local_gridfunction_coeff{}_diff{}".format(coeff.count(), diffOrder)
     define_gridfunction_member(name, coeff, diffOrder)
     return name
 
@@ -175,14 +175,14 @@ def define_gridfunction_member(name, coeff, diffOrder):
     _type = type_gridfunction_template_parameter(coeff)
     param = name_gridfunction_constructor_argument(coeff)
     if diffOrder > 0:
-        include_file("dune/pdelab/function/discretegridviewfunction.hh", filetag="operatorfile")
-        newtype = "Dune::PDELab::DiscreteGridViewFunction<typename {0}::GridFunctionSpace, typename {0}::Vector, {1}>".format(_type, diffOrder)
-        params = ["{}.gridFunctionSpace()".format(param), "{}.dofs()".format(param)]
-        initializer_list(name, params, classtag="operator")
-        return "{} {};".format(newtype, name)
+        other = name_gridfunction_member(coeff, diffOrder - 1)
+        init = "derivative({})".format(other)
+        initializer_list(name, [init], classtag="operator")
+        return "mutable decltype({}) {};".format(init, name)
     else:
-        initializer_list(name, [param], classtag="operator")
-        return "const {}& {};".format(_type, name)
+        init = "localFunction({})".format(param)
+        initializer_list(name, [init], classtag="operator")
+        return "mutable typename {}::LocalFunction {};".format(_type, name)
 
 
 @template_parameter(classtag="operator")