VtkHdfPostProcessor.cc

// -*- tab-width: 2; indent-tabs-mode: nil; coding: utf-8-with-signature -*-
//-----------------------------------------------------------------------------
// Copyright 2000-2026 CEA (www.cea.fr) IFPEN (www.ifpenergiesnouvelles.com)
// See the top-level COPYRIGHT file for details.
// SPDX-License-Identifier: Apache-2.0
//-----------------------------------------------------------------------------
/*---------------------------------------------------------------------------*/
/* VtkHdfPostProcessor.cc                                      (C) 2000-2026 */
/*                                                                           */
/* Post-processing in VTK HDF format.                                        */
/*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*/
 
#include "arcane/utils/Collection.h"
#include "arcane/utils/Enumerator.h"
#include "arcane/utils/Iostream.h"
#include "arcane/utils/ScopedPtr.h"
#include "arcane/utils/StringBuilder.h"
#include "arcane/utils/CheckedConvert.h"
#include "arcane/utils/JSONWriter.h"
#include "arcane/utils/IOException.h"
 
#include "arcane/core/PostProcessorWriterBase.h"
#include "arcane/core/Directory.h"
#include "arcane/core/FactoryService.h"
#include "arcane/core/IDataWriter.h"
#include "arcane/core/IData.h"
#include "arcane/core/IItemFamily.h"
#include "arcane/core/VariableCollection.h"
#include "arcane/core/IParallelMng.h"
#include "arcane/core/IMesh.h"
#include "arcane/core/internal/VtkCellTypes.h"
 
#include "arcane/hdf5/Hdf5Utils.h"
#include "arcane/hdf5/VtkHdfPostProcessor_axl.h"
 
// This format is described on the following webpage:
//
// https://kitware.github.io/vtk-examples/site/VTKFileFormats/#hdf-file-formats
 
/*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*/
 
// TODO: Look into saving uniqueId() (via vtkOriginalCellIds)
// TODO: Look into how to avoid saving the mesh in every iteration if it
//       doesn't change. With the concept of HDF5 linking, it should be possible
//       to store this information elsewhere and only save the mesh
//       if it evolves.
// TODO: Look into compression
 
/*
  NOTE on parallel implementation
 
  The current implementation is very basic.
  Only the master rank (rank 0 generally) performs the outputs. For
  each dataset, this rank performs a gather to retrieve the information. This
  therefore assumes that everyone has the same variables and in the same order
  (normally this is always the case because it is sorted by the VariableMng).
 
  This implementation therefore works regardless of the message exchange mode
  used (full MPI, shared memory, or hybrid).
 
  TODO: Decouple the writing from variable management to be able to use
  HDF5 collective operations (if compiled with MPI). In this case, it
  is still necessary to manually manage the message exchange mode in shared memory
  or hybrid.
*/
/*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*/
 
namespace Arcane
{
using namespace Hdf5Utils;
 
/*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*/
 
class VtkHdfDataWriter
: public TraceAccessor
, public IDataWriter
{
 public:
 
  VtkHdfDataWriter(IMesh* mesh, ItemGroupCollection groups);
 
 public:
 
  void beginWrite(const VariableCollection& vars) override;
  void endWrite() override;
  void setMetaData(const String& meta_data) override;
  void write(IVariable* var, IData* data) override;
 
 public:
 
  void setTimes(RealConstArrayView times) { m_times = times; }
  void setDirectoryName(const String& dir_name) { m_directory_name = dir_name; }
 
 private:
 
  IMesh* m_mesh;

  ItemGroupCollection m_groups;

  UniqueArray<Real> m_times;

  String m_full_filename;

  String m_directory_name;

  HFile m_file_id;
 
  HGroup m_cell_data_group;
  HGroup m_node_data_group;
  bool m_is_parallel = false;
  bool m_is_master_io = false;
  bool m_is_collective_io = false;
 
 private:
 
  void _addInt64ArrayAttribute(Hid& hid, const char* name, Span<const Int64> values);
  void _addStringAttribute(Hid& hid, const char* name, const String& value);
 
  template <typename DataType> void
  _writeDataSet1D(HGroup& group, const String& name, Span<const DataType> values);
  template <typename DataType> void
  _writeDataSet1DCollective(HGroup& group, const String& name, Span<const DataType> values);
  template <typename DataType> void
  _writeDataSet2D(HGroup& group, const String& name, Span2<const DataType> values);
  template <typename DataType> void
  _writeDataSet2DCollective(HGroup& group, const String& name, Span2<const DataType> values);
  template <typename DataType> void
  _writeBasicTypeDataset(HGroup& group, IVariable* var, IData* data);
  void _writeReal3Dataset(HGroup& group, IVariable* var, IData* data);
  void _writeReal2Dataset(HGroup& group, IVariable* var, IData* data);
 
  template <typename DataType> void
  _writeDataSet1DCollectiveWithCollectiveIO(HGroup& group, const String& name, Span<const DataType> values);
  template <typename DataType> void
  _writeDataSet2DCollectiveWithCollectiveIO(HGroup& group, const String& name, Span2<const DataType> values);
 
  String _getFileNameForTimeIndex(Int32 index)
  {
    StringBuilder sb(m_mesh->name());
    if (index >= 0) {
      sb += "_";
      sb += index;
    }
    sb += ".hdf";
    return sb.toString();
  }
};
 
/*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*/
 
VtkHdfDataWriter::
VtkHdfDataWriter(IMesh* mesh, ItemGroupCollection groups)
: TraceAccessor(mesh->traceMng())
, m_mesh(mesh)
, m_groups(groups)
{
}
 
/*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*/
 
void VtkHdfDataWriter::
beginWrite(const VariableCollection& vars)
{
  ARCANE_UNUSED(vars);
 
  IParallelMng* pm = m_mesh->parallelMng();
  const Int32 nb_rank = pm->commSize();
  m_is_parallel = nb_rank > 1;
  m_is_master_io = pm->isMasterIO();
 
  Int32 time_index = m_times.size();
  const bool is_first_call = (time_index < 2);
  if (is_first_call)
    pwarning() << "The 'VtkHdf' format implementation is experimental";
 
  String filename = _getFileNameForTimeIndex(time_index);
 
  Directory dir(m_directory_name);
 
  m_full_filename = dir.file(filename);
  info(4) << "VtkHdfDataWriter::beginWrite() file=" << m_full_filename;
 
  HInit();
  HInit::useMutex(pm->isThreadImplementation(), pm);
 
  HGroup top_group;
 
  // TODO: protect concurrent HDF5 calls
  // It is possible to use HDF5 collective mode via MPI-IO in the following cases:
  // - Hdf5 was compiled with MPI
  // - we are in pure MPI mode (neither shared memory mode nor hybrid mode)
  m_is_collective_io = pm->isParallel() && HInit::hasParallelHdf5();
  if (pm->isHybridImplementation() || pm->isThreadImplementation())
    m_is_collective_io = false;
  if (is_first_call)
    info() << "VtkHdfDataWriter: using collective MPI/IO ?=" << m_is_collective_io;
 
  HProperty plist_id;
  if (m_is_collective_io)
    plist_id.createFilePropertyMPIIO(pm);
 
  if (time_index <= 1) {
    if (m_is_master_io) {
      dir.createDirectory();
    }
  }
 
  if (m_is_collective_io)
    pm->barrier();
 
  if (m_is_collective_io || m_is_master_io) {
    m_file_id.openTruncate(m_full_filename, plist_id.id());
 
    top_group.create(m_file_id, "VTKHDF");
 
    m_cell_data_group.create(top_group, "CellData");
    m_node_data_group.create(top_group, "PointData");
 
    std::array<Int64, 2> version = { 1, 0 };
    _addInt64ArrayAttribute(top_group, "Version", version);
    _addStringAttribute(top_group, "Type", "UnstructuredGrid");
  }
 
  CellGroup all_cells = m_mesh->allCells();
  NodeGroup all_nodes = m_mesh->allNodes();
 
  const Int32 nb_cell = all_cells.size();
  const Int32 nb_node = all_nodes.size();
 
  Int32 total_nb_connected_node = 0;
  {
    ENUMERATE_CELL (icell, all_cells) {
      Cell cell = *icell;
      total_nb_connected_node += cell.nodeIds().size();
    }
  }
 
  // For connectivities, the array size is equal
  // to the number of cells plus 1.
  UniqueArray<Int64> cells_connectivity(total_nb_connected_node);
  UniqueArray<Int64> cells_offset(nb_cell + 1);
  UniqueArray<unsigned char> cells_ghost_type(nb_cell);
  UniqueArray<unsigned char> cells_type(nb_cell);
  UniqueArray<Int64> cells_uid(nb_cell);
  cells_offset[0] = 0;
  {
    Int32 connected_node_index = 0;
    ENUMERATE_CELL (icell, all_cells) {
      Int32 index = icell.index();
      Cell cell = *icell;
 
      cells_uid[index] = icell->uniqueId();
 
      Byte ghost_type = 0;
      bool is_ghost = !cell.isOwn();
      if (is_ghost)
        ghost_type = VtkUtils::CellGhostTypes::DUPLICATECELL;
      cells_ghost_type[index] = ghost_type;
 
      unsigned char vtk_type = VtkUtils::arcaneToVtkCellType(cell.type());
      cells_type[index] = vtk_type;
      for (NodeLocalId node : cell.nodeIds()) {
        cells_connectivity[connected_node_index] = node;
        ++connected_node_index;
      }
      cells_offset[index + 1] = connected_node_index;
    }
  }
 
  _writeDataSet1DCollective<Int64>(top_group, "Offsets", cells_offset);
 
  _writeDataSet1DCollective<Int64>(top_group, "Connectivity", cells_connectivity);
  _writeDataSet1DCollective<unsigned char>(top_group, "Types", cells_type);
 
  {
    UniqueArray<Int64> nb_cell_by_ranks(1);
    nb_cell_by_ranks[0] = nb_cell;
    _writeDataSet1DCollective<Int64>(top_group, "NumberOfCells", nb_cell_by_ranks);
 
    UniqueArray<Int64> nb_node_by_ranks(1);
    nb_node_by_ranks[0] = nb_node;
    _writeDataSet1DCollective<Int64>(top_group, "NumberOfPoints", nb_node_by_ranks);
 
    UniqueArray<Int64> number_of_connectivity_ids(1);
    number_of_connectivity_ids[0] = cells_connectivity.size();
    _writeDataSet1DCollective<Int64>(top_group, "NumberOfConnectivityIds", number_of_connectivity_ids);
  }
 
  // Save the uniqueIds, types, and coordinates of the nodes.
  {
    UniqueArray<Int64> nodes_uid(nb_node);
    UniqueArray<unsigned char> nodes_ghost_type(nb_node);
    VariableNodeReal3& nodes_coordinates(m_mesh->nodesCoordinates());
    UniqueArray2<Real> points;
    points.resize(nb_node, 3);
    ENUMERATE_NODE (inode, all_nodes) {
      Int32 index = inode.index();
      Node node = *inode;
 
      nodes_uid[index] = inode->uniqueId();
 
      Byte ghost_type = 0;
      bool is_ghost = !node.isOwn();
      if (is_ghost)
        ghost_type = VtkUtils::PointGhostTypes::DUPLICATEPOINT;
      nodes_ghost_type[index] = ghost_type;
 
      Real3 pos = nodes_coordinates[inode];
      points[index][0] = pos.x;
      points[index][1] = pos.y;
      points[index][2] = pos.z;
    }
 
    // Save the uniqueId of each node in the "GlobalNodeId" dataset.
    _writeDataSet1DCollective<Int64>(m_node_data_group, "GlobalNodeId", nodes_uid);
 
    // Save the information about the node type (real or ghost).
    _writeDataSet1DCollective<unsigned char>(m_node_data_group, "vtkGhostType", nodes_ghost_type);
 
    // Save the coordinates of the nodes.
    _writeDataSet2DCollective<Real>(top_group, "Points", points);
  }
 
  // Save the information about the cell type (real or ghost)
  _writeDataSet1DCollective<Int64>(m_cell_data_group, "GlobalCellId", cells_uid);
 
  // Save the uniqueId of each cell in the "GlobalCellId" dataset.
  // The use of the "vtkOriginalCellIds" dataset does not work in Paraview.
  _writeDataSet1DCollective<unsigned char>(m_cell_data_group, "vtkGhostType", cells_ghost_type);
}
 
/*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*/
 
namespace
{
  template <typename DataType> class HDFTraits;
 
  template <> class HDFTraits<Int64>
  {
   public:
 
    static hid_t hdfType() { return H5T_NATIVE_INT64; }
  };
 
  template <> class HDFTraits<Int32>
  {
   public:
 
    static hid_t hdfType() { return H5T_NATIVE_INT32; }
  };
 
  template <> class HDFTraits<double>
  {
   public:
 
    static hid_t hdfType() { return H5T_NATIVE_DOUBLE; }
  };
 
  template <> class HDFTraits<unsigned char>
  {
   public:
 
    static hid_t hdfType() { return H5T_NATIVE_UINT8; }
  };
 
} // namespace
 
/*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*/
 
template <typename DataType> void VtkHdfDataWriter::
_writeDataSet1DCollectiveWithCollectiveIO(HGroup& group, const String& name, Span<const DataType> values)
{
  IParallelMng* pm = m_mesh->parallelMng();
  Int64 size = values.size();
  Int32 nb_rank = pm->commSize();
  Int32 my_rank = pm->commRank();
  UniqueArray<Int64> all_sizes(nb_rank);
  pm->allGather(ConstArrayView<Int64>(1, &size), all_sizes);
 
  Int64 total_size = 0;
  for (Integer i = 0; i < nb_rank; ++i)
    total_size += all_sizes[i];
  Int64 my_index = 0;
  for (Integer i = 0; i < my_rank; ++i)
    my_index += all_sizes[i];
  //m_variables_offset.insert(std::make_pair(v->fullName(), VarOffset(my_index, total_size, all_sizes)));
  //info() << " ADD OFFSET v=" << v->fullName() << " offset=" << my_index
  //       << "  total_size=" << total_size;
 
  hsize_t offset[1];
  hsize_t count[1];
  offset[0] = my_index;
  count[0] = size;
 
  hsize_t dims[1];
  dims[0] = total_size;
  HSpace filespace_id;
  filespace_id.createSimple(1, dims);
  HSpace memspace_id;
  memspace_id.createSimple(1, count);
 
  HDataset dataset_id;
  const hid_t hdf_type = HDFTraits<DataType>::hdfType();
 
  dataset_id.create(group, name.localstr(), hdf_type, filespace_id, H5P_DEFAULT);
 
  H5Sselect_hyperslab(filespace_id.id(), H5S_SELECT_SET, offset, NULL, count, NULL);
 
  HProperty write_plist_id;
  write_plist_id.createDatasetTransfertCollectiveMPIIO();
 
  herr_t herr = dataset_id.write(hdf_type, values.data(), memspace_id, filespace_id, write_plist_id);
 
  if (herr < 0)
    ARCANE_THROW(IOException, "Can not write dataset '{0}'", name);
}
 
/*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*/
 
template <typename DataType> void VtkHdfDataWriter::
_writeDataSet2DCollectiveWithCollectiveIO(HGroup& group, const String& name, Span2<const DataType> values)
{
  IParallelMng* pm = m_mesh->parallelMng();
  Int64 dim1_size = values.dim1Size();
  Int64 dim2_size = values.dim2Size();
  Int32 nb_rank = pm->commSize();
  Int32 my_rank = pm->commRank();
  UniqueArray<Int64> all_sizes(nb_rank);
  pm->allGather(ConstArrayView<Int64>(1, &dim1_size), all_sizes);
 
  Int64 total_size = 0;
  for (Integer i = 0; i < nb_rank; ++i)
    total_size += all_sizes[i];
  Int64 my_index = 0;
  for (Integer i = 0; i < my_rank; ++i)
    my_index += all_sizes[i];
  //m_variables_offset.insert(std::make_pair(v->fullName(), VarOffset(my_index, total_size, all_sizes)));
  //info() << " ADD OFFSET v=" << v->fullName() << " offset=" << my_index
  //       << "  total_size=" << total_size;
 
  hsize_t offset[2];
  hsize_t count[2];
  offset[0] = my_index;
  offset[1] = 0;
  count[0] = dim1_size;
  count[1] = dim2_size;
 
  hsize_t dims[2];
  dims[0] = total_size;
  dims[1] = dim2_size;
  HSpace filespace_id;
  filespace_id.createSimple(2, dims);
  HSpace memspace_id;
  memspace_id.createSimple(2, count);
 
  HDataset dataset_id;
  const hid_t hdf_type = HDFTraits<DataType>::hdfType();
 
  dataset_id.create(group, name.localstr(), hdf_type, filespace_id, H5P_DEFAULT);
 
  H5Sselect_hyperslab(filespace_id.id(), H5S_SELECT_SET, offset, NULL, count, NULL);
 
  HProperty write_plist_id;
  write_plist_id.createDatasetTransfertCollectiveMPIIO();
 
  herr_t herr = dataset_id.write(hdf_type, values.data(), memspace_id, filespace_id, write_plist_id);
 
  if (herr < 0)
    ARCANE_THROW(IOException, "Can not write dataset '{0}'", name);
}
 
/*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*/
 
template <typename DataType> void VtkHdfDataWriter::
_writeDataSet1D(HGroup& group, const String& name, Span<const DataType> values)
{
  hsize_t dims[1];
  dims[0] = values.size();
  HSpace hspace;
  hspace.createSimple(1, dims);
  HDataset dataset;
  const hid_t hdf_type = HDFTraits<DataType>::hdfType();
  dataset.create(group, name.localstr(), hdf_type, hspace, H5P_DEFAULT);
  dataset.write(hdf_type, values.data());
  if (dataset.isBad())
    ARCANE_THROW(IOException, "Can not write dataset '{0}'", name);
}
 
/*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*/
 
template <typename DataType> void VtkHdfDataWriter::
_writeDataSet1DCollective(HGroup& group, const String& name, Span<const DataType> values)
{
  if (!m_is_parallel) {
    _writeDataSet1D(group, name, values);
    return;
  }
  if (m_is_collective_io) {
    _writeDataSet1DCollectiveWithCollectiveIO(group, name, values);
    return;
  }
  UniqueArray<DataType> all_values;
  IParallelMng* pm = m_mesh->parallelMng();
  pm->gatherVariable(values.smallView(), all_values, pm->masterIORank());
  if (m_is_master_io)
    _writeDataSet1D<DataType>(group, name, all_values);
}
 
/*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*/
 
template <typename DataType> void VtkHdfDataWriter::
_writeDataSet2D(HGroup& group, const String& name, Span2<const DataType> values)
{
  hsize_t dims[2];
  dims[0] = values.dim1Size();
  dims[1] = values.dim2Size();
  HSpace hspace;
  hspace.createSimple(2, dims);
  HDataset dataset;
  const hid_t hdf_type = HDFTraits<DataType>::hdfType();
  dataset.create(group, name.localstr(), hdf_type, hspace, H5P_DEFAULT);
  dataset.write(hdf_type, values.data());
  if (dataset.isBad())
    ARCANE_THROW(IOException, "Can not write dataset '{0}'", name);
}
 
/*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*/
 
template <typename DataType> void VtkHdfDataWriter::
_writeDataSet2DCollective(HGroup& group, const String& name, Span2<const DataType> values)
{
  Int64 dim2_size = values.dim2Size();
 
  if (!m_is_parallel) {
    _writeDataSet2D(group, name, values);
    return;
  }
 
  if (m_is_collective_io) {
    _writeDataSet2DCollectiveWithCollectiveIO(group, name, values);
    return;
  }
 
  UniqueArray<DataType> all_values;
  IParallelMng* pm = m_mesh->parallelMng();
  Span<const DataType> values_1d(values.data(), values.totalNbElement());
  pm->gatherVariable(values_1d.smallView(), all_values, pm->masterIORank());
  if (m_is_master_io) {
    Int64 dim1_size = all_values.size();
    if (dim2_size != 0)
      dim1_size = dim1_size / dim2_size;
    Span2<const DataType> span2(all_values.data(), dim1_size, dim2_size);
    _writeDataSet2D<DataType>(group, name, span2);
  }
}
 
/*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*/
 
void VtkHdfDataWriter::
_addInt64ArrayAttribute(Hid& hid, const char* name, Span<const Int64> values)
{
  hsize_t len = values.size();
  hid_t aid = H5Screate_simple(1, &len, 0);
  hid_t attr = H5Acreate2(hid.id(), name, H5T_NATIVE_INT64, aid, H5P_DEFAULT, H5P_DEFAULT);
  if (attr < 0)
    ARCANE_FATAL("Can not create attribute '{0}'", name);
  int ret = H5Awrite(attr, H5T_NATIVE_INT64, values.data());
  if (ret < 0)
    ARCANE_FATAL("Can not write attribute '{0}'", name);
  H5Aclose(attr);
  H5Sclose(aid);
}
 
/*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*/
 
void VtkHdfDataWriter::
_addStringAttribute(Hid& hid, const char* name, const String& value)
{
  hid_t aid = H5Screate(H5S_SCALAR);
  hid_t attr_type = H5Tcopy(H5T_C_S1);
  H5Tset_size(attr_type, value.length());
  hid_t attr = H5Acreate2(hid.id(), name, attr_type, aid, H5P_DEFAULT, H5P_DEFAULT);
  if (attr < 0)
    ARCANE_FATAL("Can not create attribute {0}", name);
  int ret = H5Awrite(attr, attr_type, value.localstr());
  ret = H5Tclose(attr_type);
  if (ret < 0)
    ARCANE_FATAL("Can not write attribute '{0}'", name);
  H5Aclose(attr);
  H5Sclose(aid);
}
 
/*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*/
 
void VtkHdfDataWriter::
endWrite()
{
  m_cell_data_group.close();
  m_node_data_group.close();
  //top_group.close();
  m_file_id.close();
 
  // Writes the file containing the times (starting from ParaView version 5.5)
  // https://www.paraview.org/Wiki/ParaView_Release_Notes#JSON_based_new_meta_file_format_for_series_added
  //
  // Example:
  // {
  //   "file-series-version" : "1.0",
  //   "files" : [
  //     { "name" : "foo1.vtk", "time" : 0 },
  //     { "name" : "foo2.vtk", "time" : 5.5 },
  //     { "name" : "foo3.vtk", "time" : 11.2 }
  //   ]
  // }
 
  if (!m_is_master_io)
    return;
 
  JSONWriter writer(JSONWriter::FormatFlags::None);
  {
    JSONWriter::Object o(writer);
    writer.write("file-series-version", "1.0");
    writer.writeKey("files");
    writer.beginArray();
    {
      Integer file_index = 1;
      for (Real v : m_times) {
        JSONWriter::Object o(writer);
        String filename = _getFileNameForTimeIndex(file_index);
        writer.write("name", filename);
        writer.write("time", v);
        ++file_index;
      }
      writer.endArray();
    }
  }
  Directory dir(m_directory_name);
  String fname = dir.file(_getFileNameForTimeIndex(-1) + ".series");
  std::ofstream ofile(fname.localstr());
  StringView buf = writer.getBuffer();
  ofile.write(reinterpret_cast<const char*>(buf.bytes().data()), buf.length());
}
 
/*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*/
 
void VtkHdfDataWriter::
setMetaData(const String& meta_data)
{
  ARCANE_UNUSED(meta_data);
}
 
/*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*/
 
void VtkHdfDataWriter::
write(IVariable* var, IData* data)
{
  info(4) << "Write VtkHdf var=" << var->name();
 
  eItemKind item_kind = var->itemKind();
 
  if (var->dimension() != 1)
    ARCANE_FATAL("Only export of scalar item variable is implemented (name={0})", var->name());
 
  HGroup* group = nullptr;
  switch (item_kind) {
  case IK_Cell:
    group = &m_cell_data_group;
    break;
  case IK_Node:
    group = &m_node_data_group;
    break;
  default:
    ARCANE_FATAL("Only export of 'Cell' or 'Node' variable is implemented (name={0})", var->name());
  }
  ARCANE_CHECK_POINTER(group);
 
  eDataType data_type = var->dataType();
  switch (data_type) {
  case DT_Real:
    _writeBasicTypeDataset<Real>(*group, var, data);
    break;
  case DT_Int64:
    _writeBasicTypeDataset<Int64>(*group, var, data);
    break;
  case DT_Int32:
    _writeBasicTypeDataset<Int32>(*group, var, data);
    break;
  case DT_Real3:
    _writeReal3Dataset(*group, var, data);
    break;
  case DT_Real2:
    _writeReal2Dataset(*group, var, data);
    break;
  default:
    warning() << String::format("Export for datatype '{0}' is not supported (var_name={1})", data_type, var->name());
  }
}
 
/*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*/
 
template <typename DataType> void VtkHdfDataWriter::
_writeBasicTypeDataset(HGroup& group, IVariable* var, IData* data)
{
  auto* true_data = dynamic_cast<IArrayDataT<DataType>*>(data);
  ARCANE_CHECK_POINTER(true_data);
  _writeDataSet1DCollective(group, var->name(), Span<const DataType>(true_data->view()));
}
 
/*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*/
 
void VtkHdfDataWriter::
_writeReal3Dataset(HGroup& group, IVariable* var, IData* data)
{
  auto* true_data = dynamic_cast<IArrayDataT<Real3>*>(data);
  ARCANE_CHECK_POINTER(true_data);
  SmallSpan<const Real3> values(true_data->view());
  Int32 nb_value = values.size();
  // TODO: optimize this without passing through a temporary array
  UniqueArray2<Real> scalar_values;
  scalar_values.resize(nb_value, 3);
  for (Int32 i = 0; i < nb_value; ++i) {
    Real3 v = values[i];
    scalar_values[i][0] = v.x;
    scalar_values[i][1] = v.y;
    scalar_values[i][2] = v.z;
  }
  _writeDataSet2DCollective<Real>(group, var->name(), scalar_values);
}
 
/*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*/
 
void VtkHdfDataWriter::
_writeReal2Dataset(HGroup& group, IVariable* var, IData* data)
{
  // Convert to an array of 3 components where the last one will be 0.
  auto* true_data = dynamic_cast<IArrayDataT<Real2>*>(data);
  ARCANE_CHECK_POINTER(true_data);
  SmallSpan<const Real2> values(true_data->view());
  Int32 nb_value = values.size();
  UniqueArray2<Real> scalar_values;
  scalar_values.resize(nb_value, 3);
  for (Int32 i = 0; i < nb_value; ++i) {
    Real2 v = values[i];
    scalar_values[i][0] = v.x;
    scalar_values[i][1] = v.y;
    scalar_values[i][2] = 0.0;
  }
  _writeDataSet2DCollective<Real>(group, var->name(), scalar_values);
}
 
/*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*/
 
/*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*/
class VtkHdfPostProcessor
: public ArcaneVtkHdfPostProcessorObject
{
 public:
 
  explicit VtkHdfPostProcessor(const ServiceBuildInfo& sbi)
  : ArcaneVtkHdfPostProcessorObject(sbi)
  {
  }
 
  IDataWriter* dataWriter() override { return m_writer.get(); }
  void notifyBeginWrite() override
  {
    auto w = std::make_unique<VtkHdfDataWriter>(mesh(), groups());
    w->setTimes(times());
    Directory dir(baseDirectoryName());
    w->setDirectoryName(dir.file("vtkhdf"));
    m_writer = std::move(w);
  }
  void notifyEndWrite() override
  {
    m_writer = nullptr;
  }
  void close() override {}
 
 private:
 
  std::unique_ptr<IDataWriter> m_writer;
};
 
/*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*/
 
ARCANE_REGISTER_SERVICE_VTKHDFPOSTPROCESSOR(VtkHdfPostProcessor,
                                            VtkHdfPostProcessor);
 
/*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*/
 
} // namespace Arcane
 
/*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*/