Hello,
later , I tried to use the number of active cells,
density.reinit(triangulation.n_active_cells());
gradient.reinit(triangulation.n_active_cells());
But I still got the same issue.
In last code pasted in the first email I think I have to replace
dof_handler_ref.n_dofs() with triangulation.n_active_cells(),because
dof_handler_ref.n_dofs() is about the number of dofs instead of activae
cells.
Could anyone provide any suggestions?
Best regards
Lance
On Sunday, July 2, 2023 at 2:36:50 PM UTC+2 Lance Zhang wrote:
> Hello ,
>
> I would like to use finite difference method to calculate the gradient of
> density in cells.
>
> But I got issue when the program was processed at the part of
> compute_gradient();
>
> Here is the code below about density and gradient.
>
>
> //>>>>>>>>>>>>>>>Density>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
> template <int dim,typename NumberType>
>
> void Solid<dim,NumberType>::compute_density()
> {
> typename DoFHandler<dim>::active_cell_iterator cell =
> dof_handler_ref.begin_active(),
> endc =
> dof_handler_ref.end();
>
> for (; cell != endc; ++cell)
> {
> // Compute the grid density for each cell,
> density[cell->active_cell_index()] = 1.0 / cell->measure();
> }
> }
>
>
>
> //>>>>>>>>>>>>>>>>>>>Gradient>>>>>>>>>>>>>>>>>>>>>>>>
> template <int dim,typename NumberType>
>
>
> void Solid<dim,NumberType>::compute_gradient()
> {
> typename DoFHandler<dim>::active_cell_iterator cell =
> dof_handler_ref.begin_active(),
> endc =
> dof_handler_ref.end();
>
> for (; cell != endc; ++cell)
> {
> for (unsigned int face = 0; face < GeometryInfo<dim>::faces_per_cell;
> ++face)
> {
> if (cell->face(face)->at_boundary())
> {
> // Compute the gradient at each boundary face by differencing the
> neighboring cell densities
> const typename DoFHandler<dim>::cell_iterator neighbor =
> cell->neighbor(face);
> gradient[cell->face(face)->index()] =
> density[neighbor->active_cell_index()] - density[cell->active_cell_index()];
> }
> }
> }
> }
> //<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
>
> The error comes out at the part of compute_gradient().
>
> ----------------------------------------------------------------------------------------------------------------
> Error information:
> Thread 1 "cook_membrane" received signal SIGSEGV, Segmentation fault.
> 0x00007ffff4bfcdaa in dealii::CellAccessor<3, 3>::active_cell_index()
> const () from /lib/x86_64-linux-gnu/libdeal.ii.so.9.3.2
>
> ----------------------------------------------------------------------------------------------------------------
> I tried to reduce the numbers of grids and dofs ,but I sill got the same
> issue.
>
> in the part of void Solid<dim,NumberType>::run(),
> I add the code below
>
> template <int dim,typename NumberType>
> void Solid<dim,NumberType>::run(){
> .//other codes
> .//other codes
> .//other codes
> density.reinit(dof_handler_ref.n_dofs());
> gradient.reinit(dof_handler_ref.n_dofs());
> //<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
> print_vertical_tip_displacement();
>
> std::cout<<"Density claculation"<<std::endl;
> compute_density();//sucessfully
> std::cout<<"Gradient calculation"<<std::endl;
> compute_gradient();//error comes out
> }
>
> Could anyone provide any hint or suggestions?
>
> Thanks in advance!
> Best regards
> Lance
>
>
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