message: use updated operator
diff: @@ -43,6 +43,7 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  #include <ginkgo/core/matrix/dense.hpp>
  #include <ginkgo/core/matrix/identity.hpp>
  #include <ginkgo/core/matrix/row_gatherer.hpp>
  +#include <ginkgo/core/matrix/sparsity_csr.hpp>
  #include "core/base/utils.hpp"
  @@ -161,6 +162,16 @@ void AmgxPgm<ValueType, IndexType>::generate()
  one<ValueType>()));
  // TODO: implement the restrict_op from aggregation.
  auto restrict_op = gko::as<csr_type>(share(prolong_csr->transpose()));
  + auto restrict_sparsity =
  + share(matrix::SparsityCsr<ValueType, IndexType>::create(
  + exec, restrict_op->get_size(),
  + restrict_op->get_num_stored_elements()));
  + exec->copy_from(exec.get(), static_cast<size_type>(num_agg + 1),
  + restrict_op->get_const_row_ptrs(),
  + restrict_sparsity->get_row_ptrs());
  + exec->copy_from(exec.get(), restrict_op->get_num_stored_elements(),
  + restrict_op->get_const_col_idxs(),
  + restrict_sparsity->get_col_idxs());
  // Construct the coarse matrix
  // TODO: use less memory footprint to improve it
  @@ -170,7 +181,8 @@ void AmgxPgm<ValueType, IndexType>::generate()
  amgxpgm_op->apply(prolong_csr.get(), tmp.get());
  restrict_op->apply(tmp.get(), coarse_matrix.get());
  - this->set_multigrid_level(prolong_row_gather, coarse_matrix, restrict_op);
  + this->set_multigrid_level(prolong_row_gather, coarse_matrix,
  + restrict_sparsity);
  }
  