message: Re-add diagonal preconditioner for mass in ex9
diff: @@ -371,10 +371,10 @@ int main(int argc, char *argv[])
  // Implementation of class FE_Evolution
  -FE_Evolution::FE_Evolution(Operator &_M, Operator &_K, const Vector &_b, Solver& prec)
  - : TimeDependentOperator(_M.Height()), M(_M), K(_K), b(_b), z(_M.Height()), prec(prec)
  +FE_Evolution::FE_Evolution(Operator &_M, Operator &_K, const Vector &_b, Solver& prec_)
  + : TimeDependentOperator(_M.Height()), M(_M), K(_K), b(_b), prec(prec_), z(_M.Height())
  {
  - // M_solver.SetPreconditioner(prec);
  + M_solver.SetPreconditioner(prec);
  M_solver.SetOperator(M);
  M_solver.iterative_mode = false;
  