Hello Daniel,
thanks for your message.
I wrote a statement to check if the cell exists.
for (const auto &cell : solid_3d.dof_handler_ref.active_cell_iterators())
{
//***********************************************************************************************************************************//
if(cell->at_boundary()){
continue;
}//to check whether the cell exists
//**********************filter if the cell is at boundary ,if yes, the cell
iterator will move forward*************************************//
//*******otherwise if the cell exists,the cell index will be
calculated*************************************************************//
const unsigned int cell_index = cell->active_cell_index();
if (visited_cells[cell_index])
continue; // Skip if the cell has been visited by its all
neighbors
// Loop over all degrees of freedom on the current cell
for (unsigned int i = 0; i < solid_3d.dofs_per_cell; ++i)
{
// Loop over all neighboring cells
for (unsigned int f = 0; f < cell->n_faces(); ++f)
{
auto neighbor = cell->neighbor(f);//find the neighbor ,but not
sure if it exists
if(neighbor->at_boundary())
continue;//check if the neighbor of cell exists
int neighbor_index = neighbor->active_cell_index();//get the
global index of the cell if it exists
Best regards
Lance
On Wednesday, November 29, 2023 at 6:04:45 PM UTC+2 d.arnd...@gmail.com
wrote:
> Lance,
>
> You would check for the cell being at a boundary first before asking for
> its neighbor:
>
> // Loop over all neighboring cells
> for (unsigned int f = 0; f < cell->n_faces(); ++f)
> {
> if (cell->at_boundary(f))
> continue;
> auto neighbor = cell->neighbor(f);
> int neighbor_index = neighbor->active_cell_index();//get the
> global index of the cell if it exists
> [...]
>
>
> Best,
> Daniel
>
> On Wed, Nov 29, 2023 at 9:43 AM Lance Zhang <dim...@gmail.com> wrote:
>
>> Hello Wolfgang,
>>
>> thanks for your message.
>>
>> May I know which method or keywords can be used to stand for the
>> non-existing cell and could I use cell->at_boundary() to check whether
>> the cell exists or not?
>>
>> I would like to know how we can identify if the object
>> of
>> dealii::IteratorRange<dealii::TriaActiveIterator<dealii::DoFCellAccessor<3,
>> 3, false> > >::IteratorOverIterators does not exist. I have tried ==NULL
>> and nullptr, however, it doe snot work.
>>
>> There is the code snippet below, please take a look:
>>
>> for (const auto &cell : solid_3d.dof_handler_ref.active_cell_iterators())
>> {
>>
>> if(cell->at_boundary()){
>> continue;
>> }//to check whether the cell exists
>>
>> const unsigned int cell_index = cell->active_cell_index();
>>
>> if (visited_cells[cell_index])
>> continue; // Skip if the cell has been visited by its all
>> neighbors
>>
>> // Loop over all degrees of freedom on the current cell
>> for (unsigned int i = 0; i < solid_3d.dofs_per_cell; ++i)
>> {
>>
>> // Loop over all neighboring cells
>> for (unsigned int f = 0; f < cell->n_faces(); ++f)
>> {
>> auto neighbor = cell->neighbor(f);//find the neighbor ,but
>> not sure if it exists
>>
>> if(neighbor->at_boundary())
>> continue;//check if the neighbor of cell exists
>> int neighbor_index = neighbor->active_cell_index();//get the
>> global index of the cell if it exists
>> ...
>>
>> The whole code can be found via the link :
>> https://github.com/Lancelof2019/cook_membrane_snippet/blob/main/code_snippet.cpp
>>
>> Thanks in advance!
>>
>> Best regards
>> Lance
>>
>> Wolfgang Bangerth <bang...@colostate.edu> 于2023年11月28日周二 01:54写道：
>>
>>>
>>> On 11/27/23 14:52, Lance Zhang wrote:
>>> >
>>> > May I know how to find the neighbor of a cell?
>>> >
>>> > Here is one part of my code:
>>> >
>>> ----------------------------------------------------------------------------------------------------------------------
>>> > for (const auto &cell :
>>> solid_3d.get_dof_handler().active_cell_iterators()
>>> > {
>>> > const unsigned int cell_index = cell->active_cell_index();
>>> >
>>> > // Loop over all degrees of freedom on the current cell
>>> > for (unsigned int i = 0; i < dofs_per_cell.dofs_per_cell; ++i)
>>> > {
>>> > // Loop over all neighboring cells
>>> > for (const auto &neighbor : Find_neighbors?)){
>>>
>>> You can write this as
>>> for (unsigned int f=0; f<cell->n_faces(); ++f)
>>> {
>>> DoFHandler::cell_iterator neighbor = cell->neighbor(f);
>>> ...
>>> }
>>>
>>> Best
>>> W.
>>>
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