Method SplitDataSet

Filters/ParallelDIY2/vtkRedistributeDataSetFilter.cxx:929–1006

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//------------------------------------------------------------------------------
vtkSmartPointer<vtkPartitionedDataSet> vtkRedistributeDataSetFilter::SplitDataSet(
  vtkDataSet* dataset, const vtkPartitioningStrategy::PartitionInformation& info)
{
  if (!dataset || info.NumberOfPartitions == 0 || dataset->GetNumberOfCells() == 0)
  {
    vtkNew<vtkPartitionedDataSet> result;
    result->SetNumberOfPartitions(static_cast<unsigned int>(info.NumberOfPartitions));
    return result;
  }

  const auto numCells = dataset->GetNumberOfCells();
  const bool duplicate_cells =
    this->GetBoundaryMode() != vtkRedistributeDataSetFilter::ASSIGN_TO_ONE_REGION;

  // cell_ownership value should be set to -1 is the cell doesn't belong to any cut
  // else it's set to the index of the correct partition.
  vtkSmartPointer<vtkIdTypeArray> cell_ownership;
  if (duplicate_cells)
  {
    // unless duplicating cells along boundary, no need to set the
    // cell_ownership array. cell_ownership array is used to mark ghost cells
    // later on which don't exist if boundary cells are not duplicated.
    cell_ownership = info.TargetPartitions;
    cell_ownership->SetName(CELL_OWNERSHIP_ARRAYNAME);
  }

  // convert cell_regions to a collection of cell-ids for each region so that we
  // can use `vtkExtractCells` to extract cells for each region.
  std::vector<std::vector<vtkIdType>> region_cell_ids(info.NumberOfPartitions);
  for (vtkIdType cellId = 0; cellId < numCells; ++cellId)
  {
    auto part = info.TargetPartitions->GetValue(cellId);
    if (part == -1)
    {
      continue;
    }
    region_cell_ids[part].emplace_back(cellId);
  }
  if (duplicate_cells)
  {
    for (vtkIdType bId = 0; bId < info.BoundaryNeighborPartitions->GetNumberOfTuples(); ++bId)
    {
      vtkIdType tup[2];
      info.BoundaryNeighborPartitions->GetTypedTuple(bId, tup);
      region_cell_ids[tup[1]].emplace_back(tup[0]);
    }
  }

  vtkNew<vtkPartitionedDataSet> result;
  result->SetNumberOfPartitions(static_cast<unsigned int>(info.NumberOfPartitions));

  // we create a clone of the input and add the
  // cell_ownership cell arrays to it so that they are propagated to each of the
  // extracted subsets and exchanged. It will be used later on to mark
  // ghost cells.
  auto clone = vtkSmartPointer<vtkDataSet>::Take(dataset->NewInstance());
  clone->ShallowCopy(dataset);
  clone->GetCellData()->AddArray(cell_ownership);