Hello everyone,
I am having problem with applying static condensation as explained in
step-44 in parallel. The objective is to employ a parallel solver. Any
guidance on the issue would be much helpful.
As of now, the code works when run on single MPI process, but fails when np
> 1. The error originates from the following part of the code where it
tries to read the elements of the tangent_matrix, which is a
PETScWrapper::MPI::BlockSparseMatrix. The issue arises trying to access the
dofs not owned by the MPI process at the boundary partition.
//-----------------------------------------------------------------------------
for (unsigned int i=0; i<dofs_per_cell; ++i)
for (unsigned int j=0; j<dofs_per_cell; ++j)
data.k_orig(i,j) = tangent_matrix.el(data.local_dof_indices[i],
data.local_dof_indices[j]);
//-----------------------------------------------------------------------------
In the case of PETScWrapper::MPI::BlockVector I can circumvent such a
problem defining a locally_relevant BlockVector as below. I am able to
print out all the elements in this way (I am not sure if this is the most
efficient way!).
//-----------------------------------------------------------------------------
// Access ghost elements in system_rhs
LA::MPI::BlockVector system_rhs_local (locally_owned_partitioning,
locally_relevant_partitioning,
mpi_communicator);
system_rhs_local = system_rhs;
// printing out all the system_rhs values for all dofs in the cell
for (unsigned int i=0; i<dofs_per_cell; ++i)
if (this_mpi_process == 1)
std::cout << " \n Cell:"
<< cell
<< ";system_rhs("<< i <<"):"
<<system_rhs_local(data.local_dof_indices[i])
<< " ; this_mpi_process: "
<< this_mpi_process << std::flush;
//-----------------------------------------------------------------------------
Below is the initialization of the tangent_matrix BlockSparseMatrix for
reference.
//-----------------------------------------------------------------------------
BlockDynamicSparsityPattern dsp(locally_relevant_partitioning);
DoFTools::make_sparsity_pattern(dof_handler, coupling, dsp, constraints,
false);
SparsityTools::distribute_sparsity_pattern(
dsp,
dof_handler.locally_owned_dofs(),
mpi_communicator,
locally_relevant_dofs);
tangent_matrix.reinit(locally_owned_partitioning,dsp, mpi_communicator);
//-----------------------------------------------------------------------------
Please let me know if any more details are needed.
Looking forward to your input.
Thank you and Regards,
Rahul G R
Post Doc - MPI PKS, Dresden
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