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When writing an integer array with the XDMF2 writer, e.g.,

import meshzoo
import numpy
import vtk
from vtk.util import numpy_support


points, cells = meshzoo.rectangle(
    xmin=0.0, xmax=1.0,
    ymin=0.0, ymax=1.0,
    nx=4, ny=4
    )

# Generate VTK mesh
mesh = vtk.vtkUnstructuredGrid()

# set points
vtk_points = vtk.vtkPoints()
# Not using a deep copy here results in a segfault.
vtk_array = numpy_support.numpy_to_vtk(points, deep=True)
vtk_points.SetData(vtk_array)
mesh.SetPoints(vtk_points)

# create cell_array. It's a one-dimensional vector with
# (num_points2, p0, p1, ... ,pk, numpoints1, p10, p11, ..., p1k, ...
numcells, num_local_nodes = cells.shape
# add cell types
cell_types = numpy.full(numcells, vtk.VTK_TRIANGLE, dtype=numpy.ubyte)
# add cell offsets
cell_offsets = numpy.arange(
    0,
    numcells * (num_local_nodes + 1),
    num_local_nodes + 1,
    dtype=numpy.int64
    )
cell_connectivity = numpy.c_[
        num_local_nodes * numpy.ones(numcells, dtype=cells.dtype),
        cells
    ].flatten()
connectivity = vtk.util.numpy_support.numpy_to_vtkIdTypeArray(
    cell_connectivity.astype(numpy.int64),
    deep=1
    )

# wrap the data into a vtkCellArray
cell_array = vtk.vtkCellArray()
cell_array.SetCells(len(cell_types), connectivity)

# Add cell data to the mesh
mesh.SetCells(
    numpy_support.numpy_to_vtk(
        cell_types,
        deep=1,
        array_type=vtk.vtkUnsignedCharArray().GetDataType()
        ),
    numpy_support.numpy_to_vtk(
        cell_offsets,
        deep=1,
        array_type=vtk.vtkIdTypeArray().GetDataType()
        ),
    cell_array
    )

# add cell data
cd = mesh.GetCellData()
cell_data = numpy.random.randint(0, 10, len(cells))
array = vtk.util.numpy_support.numpy_to_vtk(cell_data, deep=1)
array.SetName('my_array')
cd.AddArray(array)

writer = vtk.vtkXdmfWriter()
writer.SetFileName('test.xdmf')
writer.SetInputData(mesh)
writer.Write()

one gets errors of the kind

HDF5-DIAG: Error detected in HDF5 (1.10.0-patch1) thread 0:
  #000: ../../../src/H5T.c line 1678 in H5Tcopy(): not a datatype or dataset
    major: Invalid arguments to routine
    minor: Inappropriate type
XDMF Error in /build/vtk7-mPdZCv/vtk7-7.1.1-3cf5df73/ThirdParty/xdmf2/vtkxdmf2/libsrc/XdmfDataDesc.cxx line 492 (Error Creating Data Type)
HDF5-DIAG: Error detected in HDF5 (1.10.0-patch1) thread 0:
  #000: ../../../src/H5T.c line 1846 in H5Tget_class(): not a datatype
    major: Invalid arguments to routine
    minor: Inappropriate type