Hi, Dr. W. Bangerth,
I have tried the your suggestion that is to use FE_DGQ(0) to build another
finite element field.
It works even though there is till some small problems. However, I prefer
to double check the implementation with you:
I built two fem field objects.
FESystem<dim> fe; // for describing the vector-valued field (eg.
displacement)
FE_DGQ<dim> fe_dg; // for describing the cell field (eg. pesudo density in
topology optimization)
And initialize them in the initialization list of the class,
fe(FE_Q<dim>(1), dim),
fe_dg(0),
And I initialize the cell-based vector (the pesudo density in topology
optimization) as follows,
opt->locally_owned_cells= opt->dof_handler_dg.locally_owned_dofs();
DoFTools::extract_locally_relevant_dofs(opt->dof_handler_dg,
opt->locally_relevant_cells);
opt->x.reinit(opt->locally_owned_cells,
opt->locally_relevant_cells,
opt->mpi_communicator);
Is this process correct?
Moreover, I wonder how to access opt->x by the cell ("cell" represents the
cell iterator)?
My attempting solution is to use the syntax of PETSc directly as follows,
PetscScalar *xp;
VecGetArray(opt->x, &xp); // getting a local array of the global vector
But when I access it by
xp[cell->active_cell_index()]
I got error:
Abort: Memory balance (p4est)
Abort: ../../zzd_Software_Installation_Packages/p4est-2.2/sc/src/sc.c:705
Abort
Abort: Memory balance (p4est)
Abort: ../../zzd_Software_Installation_Packages/p4est-2.2/sc/src/sc.c:705
Abort
Abort: Memory balance (p4est)
Abort: ../../zzd_Software_Installation_Packages/p4est-2.2/sc/src/sc.c:705
Abort
Abort: Memory balance (p4est)
Abort: ../../zzd_Software_Installation_Packages/p4est-2.2/sc/src/sc.c:705
Abort
===================================================================================
= BAD TERMINATION OF ONE OF YOUR APPLICATION PROCESSES
= PID 7914 RUNNING AT zzd-tnk-4755
= EXIT CODE: 6
= CLEANING UP REMAINING PROCESSES
= YOU CAN IGNORE THE BELOW CLEANUP MESSAGES
===================================================================================
YOUR APPLICATION TERMINATED WITH THE EXIT STRING: Aborted (signal 6)
This typically refers to a problem with your application.
Please see the FAQ page for debugging suggestions
May I ask you to give me some hints on this problem?
Thank you very much in advance!
Best regards,
Zhidong Brian Zhang
On Saturday, October 19, 2019 at 10:56:47 AM UTC-4, Wolfgang Bangerth wrote:
>
>
> Zhidong,
>
> > In short, my question is how to get the cell_id properly by using CellId
> class ?
> >
> > I want to assign each cell with a different value (its pesudo density in
> > topology optimization). All the values are stored in a cell-based vector
> x,
> > which is initialized as follows,
> >
> > opt->x.reinit(opt->mpi_communicator,
> > opt->triangulation.n_global_active_cells(),
> > opt->triangulation.n_locally_owned_active_cells(),
> > false);
> >
> > Now I want to access to x value in each cell. My basic idea is to get
> the
> > cell_id and then use x(cell_id). In order to get cell_id, I found I
> should use
> > CellId class, specifically, cell->id().to_string().
>
> I think this is the wrong approach. The cell ids are used to globally
> identify
> cells, but there is no easy way to translate between cell ids and an index
> into vectors. What you want to do is create another finite element field
> that
> is piecewise constant, i.e., using FE_DGQ(0). Such fields have exactly one
> value per cell, and they can be accessed like any other field-based
> quantity.
>
> Best
> W.
>
> --
> ------------------------------------------------------------------------
> Wolfgang Bangerth email: [email protected]
> <javascript:>
> www: http://www.math.colostate.edu/~bangerth/
>
>
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