Please, ignore that this method will apply a value correspond to a common
node between two adjacent element twice. I will correct that. I just want
to be sure what I am calculating is correct or not.
On Friday, July 1, 2016 at 12:05:24 PM UTC+4:30, dealii...@gmail.com wrote:
>
> Dear Daniel
>
> My name is Pasha. Thank you for your response. I want to extract sum of
> values from system RHS ( which is a
> dealii:TrilinosWrappers::MPI::BlockVector) correspond to all degrees of
> freedom which are at the boundary. I am working with a
> parallel::distributed::Triangulation. I wrote the following code to extract
> value for component 1 at boundary 3:
>
> IndexSet in_set;
>
> std::vector<bool> component_select (n_components, false);
> component_select[1] = true;
>
> std::set< types::boundary_id > boundary_ids;
> boundary_ids.insert(3);
>
> DoFTools::extract_boundary_dofs(dof_handler, component_select,
> in_set, boundary_ids);
>
> typename DoFHandler<dim>::active_cell_iterator
> cell = dof_handler.begin_active(),
> endc = dof_handler.end();
>
> double local_load = 0.0 ;
>
> for (; cell!=endc; ++cell)
> if (cell->is_locally_owned())
> {
> cell->get_dof_indices(local_dof_indices);
>
> dealii::IndexSet::ElementIterator
> index = in_set.begin(),
> endind = in_set.end();
>
> for (; index!=endind; ++index)
> {
> dealii::types::global_dof_index gdi = *index;
>
> unsigned int pos = find(local_dof_indices.begin(),
> local_dof_indices.end(),
> gdi) - local_dof_indices.begin();
> if(pos >= local_dof_indices.size()) {
> //not found
> continue;
> }
>
> // now DoF is in this cell
> local_load -= saved_residual(gdi);
>
> }
> }
>
> double load_value = Utilities::MPI::sum(local_load, mpi_com);
>
> is the above method correct? I am confusing because degrees of freedom on
> the boundary that belong to the locally relevant set.
> From deal II online documentation for DoFTools::extract_boundary_dofs():
> If the DofHandler object is indeed defined on a
> parallel::distributed::Triangulation, then the selected_dofs index set
> will contain only those degrees of freedom on the boundary that belong to
> the locally relevant set.
>
> *Locally relevant degrees of freedom*
>
> This concept identifies a subset of all degrees of freedom when using
> distributed meshes, see the Parallel computing with multiple processors
> using distributed memory
> <https://www.dealii.org/8.4.0/doxygen/deal.II/group__distributed.html>
> module.
> Locally relevant degrees of freedom are those that live on locally owned or
> ghost cells. Consequently, they may be owned by different processors.
>
> Thank you again,
> Pasha
>
>
> On Thursday, June 30, 2016 at 9:26:54 PM UTC+4:30, Daniel Arndt wrote:
>
>> Dear ?,
>>
>> dealii::IndexSet::ElementIterator::operator*() returns the stored
>> global_dof_index [1].
>> Therefore, all you have to do is to dereference index:
>>
>> dealii::types::global_dof_index gdi = *index
>>
>> Best,
>> Daniel
>>
>> [1]
>> https://www.dealii.org/8.4.1/doxygen/deal.II/classIndexSet_1_1ElementIterator.html#a6218ab9e8e76699fc998834bf8e006ee
>>
>> Am Donnerstag, 30. Juni 2016 15:12:00 UTC+2 schrieb dealii...@gmail.com:
>>>
>>> Hi
>>>
>>> I am trying to extract all degrees of freedom which are at the boundary
>>> and belong to specified components using DoFTools::extract_boundary_dofs()
>>> function and IndexSet for a parallel distributed triangulation. Now, how I
>>> can iterate over the IndexSet and how I can access to the Dof index in it?
>>>
>>> Something like this:
>>>
>>> dealii::IndexSet::ElementIterator index = in_set.begin(),
>>> endind
>>> = in_set.end();
>>>
>>> for (; index!=endind; ++index)
>>> {
>>> how to access to dof index here?
>>> }
>>>
>>> Thank you
>>>
>>
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