message: Add vector copy to ilu preconditioner, ensuring linearity of the preconditioner when iterative solvers are used for the triangular systems.
diff: @@ -176,9 +176,11 @@ protected:
  set_cache_to(b);
  if (!ReverseApply) {
  l_solver_->apply(b, cache_.intermediate.get());
  + x->copy_from(cache_.intermediate.get());
  u_solver_->apply(cache_.intermediate.get(), x);
  } else {
  u_solver_->apply(b, cache_.intermediate.get());
  + x->copy_from(cache_.intermediate.get());
  l_solver_->apply(cache_.intermediate.get(), x);
  }
  }
  