Daniel,

The link you provides is very helpful. Thanks. In the code, I see

solution_transfer.interpolate(distributed_solution);
constraints_hanging_nodes.distribute(distributed_solution);
solution = distributed_solution;

I am confused by the postprocessing. I think distributed_solution does not
have ghost. So, does "solution = distributed_solution" import ghost values
to solution? Postprocessing section of
http://www.dealii.org/8.4.1/doxygen/deal.II/group__distributed.html says

"To postprocess stuff therefore means that we have to tell PETSc or
Trilinos that it should also import *ghost elements*, ... Both the
PETScWrappers::MPI::Vector
<http://www.dealii.org/8.4.1/doxygen/deal.II/classPETScWrappers_1_1MPI_1_1Vector.html>
 and TrilinosWrappers::MPI::Vector
<http://www.dealii.org/8.4.1/doxygen/deal.II/classTrilinosWrappers_1_1MPI_1_1Vector.html>
class
support specifying this information (see step-40
<http://www.dealii.org/8.4.1/doxygen/deal.II/step_40.html> and step-32
<http://www.dealii.org/8.4.1/doxygen/deal.II/step_32.html>, respectively)
through the PETScWrappers::MPI::Vector::update_ghost_values() function or,
in the case of Trilinos, construction of a vector with an the locally
relevant degrees of freedom index set"

I used PETScWrappers::MPI::Vector and met a compilation error -- class
"dealii::PETScWrappers::MPI::Vector" has no member "update_ghost_values"

--Junchao Zhang

On Thu, Jul 21, 2016 at 4:00 AM, Daniel Arndt <
[email protected]> wrote:

> Junchao,
>
> You want to use parallel::distributed::SolutionTransfer instead if you are
> on a parallel::distributed::Triangulation
> Executing
> $ grep -r "parallel::distributed::SolutionTransfer" .
> in the examples folder, tells me that this object is used in step-32,
> step-42 and step-48.
> Have for example a look at how this is done in step-42::refine_grid[1].
>
> Best,
> Daniel
>
> [1]
> https://www.dealii.org/8.4.0/doxygen/deal.II/step_42.html#PlasticityContactProblemrefine_grid
>
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