There is a complication of using LA::distributed::Vector initialized with
MatrixFree::initialize_dof_vector() in Kelly estimator.
A naïve usage would lead to a problem which obviously has to do with
locally relevant cells and their dofs:
Number
dealii::LinearAlgebra::distributed::Vector<double>::operator()(const
size_type) const
The violated condition was:
partitioner->in_local_range (global_index) ||
partitioner->ghost_indices().is_element(global_index)
Additional information:
You tried to access element 4665 of a distributed vector, but this
element is not stored on the current processor. Note: The range of locally
owned elements is 0 to 4413, and there are 12 ghost elements that this
vector can access.
Martin explains
here https://github.com/dealii/dealii/pull/3329#discussion_r89073738 that
in this case LA::distributed::Vector
...holds all locally active DoFs but also some of the locally relevant
> DoFs. The selection of DoFs stored in a distributed vector initialized
> through MatrixFreeis such that one can read all degrees of freedom on all
> locally relevant elements (locally active) plus the degrees of freedom that
> contraints expand into from the locally owned cells. (Most of the locally
> relevant but not locally active dofs would never be accessed in
> matrix-vector products and result in too much data sent around.
I wonder what is the best workaround given the fact that i have quite a
number of such vectors?
What comes to mind is before doing postprocessing of solution I need to
change the set of ghost dofs to cover standard locally_relevant_dofs.
Probably the only way is to copy content into a temporary vector, then call
reinit(locally_owned, locally_relevant, mpi) and assign the content back.
Then i would use such vectors in Kelly and solution transfer.
However for the core part (solution), the vectors would still be
initialized with MatrixFree in setup_dofs() or alike after refinement and
before the solution.
Any better ways to accomplish this? Maybe implement/add
LA::distributed::Vector::set_ghost_set(const IndexSet &) but not sure it's
worth the effort.
Regards,
Denis.
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