message: Use integration rule from DGTraceIntegrator
diff: @@ -403,8 +403,19 @@ void FaceIntegrator::AssembleFaceVector(const FiniteElement &el1,
  DenseMatrix elvect2_mat(elvect.GetData() + dof1 * num_equation, dof2,
  num_equation);
  - const int order = std::max(el1.GetOrder(), el2.GetOrder());
  - const int intorder = 2 * order + 2;
  + // Integration order calculation from DGTraceIntegrator
  + int intorder;
  + if (Tr.Elem2No >= 0)
  + intorder = (min(Tr.Elem1->OrderW(), Tr.Elem2->OrderW()) +
  + 2*max(el1.GetOrder(), el2.GetOrder()));
  + else
  + {
  + intorder = Tr.Elem1->OrderW() + 2*el1.GetOrder();
  + }
  + if (el1.Space() == FunctionSpace::Pk)
  + {
  + intorder++;
  + }
  const IntegrationRule *ir = &IntRules.Get(Tr.FaceGeom, intorder);
  for (int i = 0; i < ir->GetNPoints(); i++)
  