Dear Daniel, I was just wondering if their exist a similar function to DoFTools::map_dofs_to_support_points, but that maps a vector-valued solution Vector into to a std::vector<Point<dim>> instead?
Best, Joel On Monday, August 22, 2016 at 9:03:22 PM UTC+2, Daniel Arndt wrote: > > Joel, > > You should not rely on any particular sorting of the dofs in the solution > vector. Instead you can ask the FiniteElement on each cell for the > component of a local dof by > const unsigned int component = fe.system_to_component_index(i).first; > > Apart from that the DataOut object knows about components and you can do > some postprocessing on the solution vector using DataPostprocessor [1] > > Best, > Daniel > > [1] https://dealii.org/8.4.1/doxygen/deal.II/classDataPostprocessor.html > > Am Montag, 22. August 2016 17:05:08 UTC+2 schrieb Joel Davidsson: >> >> Dear Daniel, >> >> Thank you for a very good answer, adding the fe_values_scalar and >> cell_scalar fixed the problem. >> >> I have a follow-up question about the solution I get out, how is the data >> organized in the solution vector? Say for example I want to loop over all >> the x components, how would I do that? >> >> Best, >> Joel >> >> On Friday, August 12, 2016 at 5:35:07 PM UTC+2, Daniel Arndt wrote: >>> >>> Joel, >>> >>> Yes the matrix you are assembling is a vector-valued mass matrix now. >>> For me your code is failing with >>> >>> void dealii::FEValuesBase<dim, spacedim>::get_function_gradients(const >>> InputVector&, std::vector<dealii::Tensor<1, spacedim, typename >>> InputVector::value_type> >&) const [with InputVector = >>> dealii::Vector<double>; int dim = 3; int spacedim = 3; typename >>> InputVector::value_type = double] >>> The violated condition was: >>> (fe->n_components()) == (1) >>> The name and call sequence of the exception was: >>> dealii::ExcDimensionMismatch((fe->n_components()),(1)) >>> Additional Information: >>> Dimension 3 not equal to 1 >>> >>> and this is not surprising. What you are doing is to extract the >>> gradients of a vector-valued finite element solution. The object that >>> should store this should therefore be a >>> std::vector<std::vector<Tensor<1,dim>> as you want to store for each >>> quadrature point and each component a Tensor<1,dim>. >>> >>> What you want to do is really that in "Do not work". As you have two >>> DoFHandlers, you should also have two FEValues objects and two >>> cell_iterator corresponding to the correct DoFHandler. Then you can extract >>> the gradient of your scalar field and project it onto the ansatz space for >>> the vector-valued field. This should look like: >>> >>> typename DoFHandler<dim>::active_cell_iterator cell_scalar = >>> dof_handler_scalar.begin_active(); >>> typename DoFHandler<dim>::active_cell_iterator cell = >>> dof_handler.begin_active(); >>> ... >>> >>> for (; cell!=endc; ++cell, ++cell_vector) >>> { >>> fe_values.reinit (cell); >>> fe_values_scalar.reinit (cell_scalar); >>> fe_values_scalar.get_function_gradients(test,fe_function_grad); >>> ... >>> } >>> >>> Best, >>> Daniel >>> >> -- The deal.II project is located at http://www.dealii.org/ For mailing list/forum options, see https://groups.google.com/d/forum/dealii?hl=en --- You received this message because you are subscribed to the Google Groups "deal.II User Group" group. To unsubscribe from this group and stop receiving emails from it, send an email to dealii+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
