Hi,
I have been trying to develop a parallelized implementation of the
Schnakenberg reaction-diffusion system using deal.II. This is my first
implementation using deal.II and I have been learning quite a bit from the
detailed tutorials and the amazing documentation. I initially implemented
the serial version using step-23 as the starting point which worked as
expected. Then I tried the parallel implementation, and the code runs
successfully on a single processor. When running it in with more than one
processor I obtain the following error :
An error occurred in line <1593> of file
</home/aadi/dealii-9.2.0/include/deal.II/lac/trilinos_vector.h> in
function void
dealii::TrilinosWrappers::MPI::Vector::set(dealii::TrilinosWrappers::MPI::Vector::size_type,
const size_type*, const TrilinosScalar*) The violated
condition was:
!has_ghost_elements()
Additional information:
You are trying an operation on a vector that is
only allowed if the vector has no ghost elements, but the vector you are
operating on does have ghost elements. Specifically, vectors with ghost
elements are read-only and cannot appear in operations that write into
these vectors.
The above error shows up in the section of the code where I equate the old
locally relevant solution with the current locally relevant solution after
the solve step. I have included specific details below :
1) The solution variables are defined in the following manner :
In the class definition -
*LA::MPI::Vector locally_relevant_solution_u, locally_relevant_solution_v
, locally_relevant_old_solution_u,
locally_relevant_old_solution_v ;*
In setup_system() -
*locally_relevant_solution_u.reinit(locally_owned_dofs,*
* locally_relevant_dofs,*
*
mpi_communicator);*
* locally_relevant_old_solution_u.reinit(locally_owned_dofs,*
*
locally_relevant_dofs,*
*
mpi_communicator);*
* locally_relevant_solution_v.reinit(locally_owned_dofs,*
*
locally_relevant_dofs, *
*
mpi_communicator);*
*locally_relevant_old_solution_v.reinit(locally_owned_dofs,*
* locally_relevant_dofs,*
*
mpi_communicator);*
2) Since this is a time-dependent problem, in the *run()* method of the
class the old solution variables (after the *solve()* step) are updated as :
locally_relevant_old_solution_u = locally_relevant_solution_u;
locally_relevant_old_solution_v = locally_relevant_solution_v;
Since the old and current solution variables are defined as ghost vectors
the above assignment is invalid and that's where the error shows up. The
reaction-diffusion system contains a field-dependent forcing term because
of which when the *cell_rhs* is constructed, the values in
*locally_relevant_old_solution_u* are interpolated to the Gauss points
using *get_function_values()*, and then the source term contribution is
constructed from there. So the old solution vector must itself contain
values associated with the ghost elements so that it must be a ghost
vector, and hence the issue with the assignment statement. Is there any way
to handle this? Thank you.
Best,
Aaditya
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