On 10/19/19 3:01 PM, Zhidong Brian Zhang wrote:
>
> 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?
Yes. Though it seems confusing to me that you call these variables
locally_*_cells, because they really are index sets for degrees of freedom,
not cells.
> Moreover, I wonder how to access opt->x by the cell ("cell" represents the
> cell iterator)?
You need to find out which DoF lives on the cell. So you can do
cell_dg->get_dof_indices(...)
and obtain an array of the local DoF indices (which for a DGQ(0) element has a
single element) that contains the global index of the DoF that lives on this
cell.
> 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()]
Yes, this does not work. That's because you confuse the index of the cell and
the index of the DoF that lives on it. You want the latter.
Best
W.
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