Re: [deal.II] How to find the neighbor of one cell
On 11/29/23 09:23, Lance Zhang wrote:
//***//
if(cell->at_boundary()){
continue;
}//to check whether the cell exists
I don't think this is what you want. Here, you are only asking whether
the cell has *any* faces that are at the boundary. But if you want to
know whether a cell has a neighbor across a certain face, you need to
ask whether the cell is at the boundary *at that particular face*.
Daniel's code does that.
Best
W.
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Re: [deal.II] How to find the neighbor of one cell
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 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> 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 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; fn_faces(); ++f)
>>>{
>>> DoFHandler::cell_iterator neighbor = cell->neighbor(f);
>>> ...
>>>}
>>>
>>> Best
>>> W.
>>>
>>> --
>>> 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
Re: [deal.II] How to find the neighbor of one cell
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 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 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 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; fn_faces(); ++f)
>>{
>> DoFHandler::cell_iterator neighbor = cell->neighbor(f);
>> ...
>>}
>>
>> Best
>> W.
>>
>> --
>> 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
>> ---
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>> https://groups.google.com/d/msgid/dealii/ef1fdaad-0bde-4478-8054-74df1a572c5f%40colostate.edu
>> .
>>
> --
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> .
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Re: [deal.II] How to find the neighbor of one cell
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 > >::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 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; fn_faces(); ++f)
>{
> DoFHandler::cell_iterator neighbor = cell->neighbor(f);
> ...
>}
>
> Best
> W.
>
> --
> The deal.II project is located at http://www.dealii.org/
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> .
>
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Re: [deal.II] How to find the neighbor of one cell
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; fn_faces(); ++f)
{
DoFHandler::cell_iterator neighbor = cell->neighbor(f);
...
}
Best
W.
--
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[deal.II] How to find the neighbor of one cell
Hello team,
I have one quick question.
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?)){
...
-
Thanks in advance!
Best regards
Lance
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