Use ud as the accuracy criterion

src/one-body-sample.cc

@@ -346,7 +346,7 @@ int main(int argc, char *argv[]) {
         }
         timeSteppingScheme->setup(problem_rhs, problem_iterate, problem_A);
 
-        VectorType u_saved = u_old;
+        VectorType ud_saved = ud_old;
         auto const state_fpi_max =
             parset.get<size_t>("solver.tnnmg.fixed_point_iterations");
         for (size_t state_fpi = 1; state_fpi <= state_fpi_max; ++state_fpi) {
@@ -399,11 +399,11 @@ int main(int argc, char *argv[]) {
             std::cerr << '.';
             std::cerr.flush();
           }
-          if (energyNorm.diff(u_saved, u) <
+          if (energyNorm.diff(ud_saved, ud) <
               parset.get<double>("solver.tnnmg.fixed_point_tolerance"))
             break;
           else
-            u_saved = u;
+            ud_saved = ud;
 
           if (state_fpi == state_fpi_max)
             std::cerr << "[ref = " << refinements