# Xmlunstructuredgridwriter issue with time.

**URL:** https://discourse.vtk.org/t/xmlunstructuredgridwriter-issue-with-time/3853
**Category:** Support
**Tags:** file-formats
**Created:** [July 26, 2020, 3:07am UTC](https://discourse.vtk.org/t/xmlunstructuredgridwriter-issue-with-time/3853 "2020-07-26T03:07:02Z")
**Posts on this page:** 3
**Page:** 1

<div class="post-metadata">

### Author: ![kayarre](https://discourse.vtk.org/user_avatar/discourse.vtk.org/kayarre/32/808_2.png) [@kayarre](https://discourse.vtk.org/u/kayarre)
#### Post date: [July 26, 2020, 3:07am UTC](https://discourse.vtk.org/t/xmlunstructuredgridwriter-issue-with-time/3853/1 "2020-07-26T03:07:02Z")

</div>

I have used the multi-time step feature successfully before in a python script, now I am trying to do something similar with c++.

I tried it several ways, but something weird is happening that’s causes paraview to choke on the file when I try to change the step. When I write each grid to a separate file it worked fine.

The approach I used in python was to use the vtkappendfilter to add a grid from a reader write the next time step, and then remove the appended grid, (except for the last step or else you get an error about 0 connections but 1 required.

I tried doing this similar approach as well as setting the grid via shallowcopy and deepcopy.

It writes the grids fine and loads but breaks when changing the time step in paraview.

Is there a better example out there or approach?

I will post some code when I am back at a desk computer.

---

<div class="post-metadata">

### Author: ![kayarre](https://discourse.vtk.org/user_avatar/discourse.vtk.org/kayarre/32/808_2.png) [@kayarre](https://discourse.vtk.org/u/kayarre)
#### Post date: [July 27, 2020, 4:35pm UTC](https://discourse.vtk.org/t/xmlunstructuredgridwriter-issue-with-time/3853/2 "2020-07-27T16:35:07Z")

</div>

here is how I am doing things,

```auto
  std::map<double, std::string> filemap; // populated with time and filepaths

  vtkSmartPointer<vtkXMLUnstructuredGridWriter>
    writer = vtkSmartPointer<vtkXMLUnstructuredGridWriter>::New();
  vtkSmartPointer<vtkUnstructuredGrid>
    grid_adapter = vtkSmartPointer<vtkUnstructuredGrid>::New();

  int nfiles = 31;
 
  writer->SetFileName("test.vtu");
  writer->SetNumberOfTimeSteps(filemap.size());
  writer->SetInputData(grid_adapter);
  writer->Start();
  int count = 0;
  for(auto file :: filemap) {
    // time idx input file path string
    std::cout << file.first << " " << file.second << "\n";
    char *szBuffer = new char[file.second.size()+1];
    ReadFileTest(szBuffer, TRUE, FALSE, grid_adapter);
    strcpy(szBuffer, file.second.c_str());
    writer->WriteNextTime(count);
    delete[] szBuffer;
    count += 1;
  }

```

the main part of `ReadFileTest()`

```auto
       vtkSmartPointer<vtkUnstructuredGrid>
          grid = vtkSmartPointer<vtkUnstructuredGrid>::New();
        grid->SetPoints(points);
        grid->SetCells(celltypes, cells);
        for (int k = 0; k < pt_data_arrays.size(); ++k)
        {
          grid->GetPointData()->AddArray(pt_data_arrays.at(k));
        }
        grid->GetCellData()->AddArray(zone_label);
        // grid->BuildLinks(); // this doesn't change anything.
        grid_adapter->ShallowCopy(grid); // does the same for either DeepCopy or ShallowCopy

```

trying to do more than load the initial file in Paraview causes a segfault, here is the truncated error log

```auto
( 24.769s) [paraview]vtkUnstructuredGridGeom:1200 ERR| vtkUnstructuredGridGeometryFilter (0xabe69b0): Cell type UnknownClass(49) is not a 3D cell.
...
( 24.771s) [paraview]vtkHigherOrderWedge.cxx:1240 ERR| vtkBezierWedge (0xbe7b1b0): The degrees are not correctly set in the input file.
...
( 24.772s) [paraview]vtkUnstructuredGridGeom:1200 ERR| vtkUnstructuredGridGeometryFilter (0xabe69b0): Cell type UnknownClass(164) is not a 3D cell.
...
( 24.777s) [paraview]vtkUnstructuredGridGeom:1200 ERR| vtkUnstructuredGridGeometryFilter (0xabe69b0): Cell type vtkHigherOrderWedge(65) is not a 3D cell.
( 24.777s) [paraview]vtkHigherOrderWedge.cxx:1240 ERR| vtkBezierWedge (0xbe7b1b0): The degrees are not correctly set in the input file.
( 24.777s) [paraview]vtkHigherOrderWedge.cxx:1262 ERR| vtkBezierWedge (0xbe7b1b0): The degrees might be direction dependents, and should be set before GetOrder is called. numPts is 8 and Order[3] 6
...
( 24.835s) [paraview]vtkUnstructuredGridGeom:1200 ERR| vtkUnstructuredGridGeometryFilter (0xabe69b0): Cell type UnknownClass(120) is not a 3D cell.

Loguru caught a signal: SIGSEGV
Stack trace:
71 0x407a7d /home/krs/tools/ParaView-5.8.0-MPI-Linux-Python3.7-64bit/bin/paraview() [0x407a7d]
70 0x7fcfc8388b97 __libc_start_main + 231
69 0x40774d /home/krs/tools/ParaView-5.8.0-MPI-Linux-Python3.7-64bit/bin/paraview() [0x40774d]
68 0x7fcfc5eed0b4 QCoreApplication::exec() + 132
67 0x7fcfc5ee44aa QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) + 234
66 0x7fcf96559e96 /media/store/krs/tools/ParaView-5.8.0-MPI-Linux-Python3.7-64bit/plugins/platforms/../../lib/libQt5XcbQpa.so.5(+0xb1e96) [0x7fcf96559e96]
65 0x7fcfc631862b QWindowSystemInterface::sendWindowSystemEvents(QFlags<QEventLoop::ProcessEventsFlag>) + 187
64 0x7fcfc633cc15 QGuiApplicationPrivate::processWindowSystemEvent(QWindowSystemInterfacePrivate::WindowSystemEvent*) + 261
63 0x7fcfc633b1a3 QGuiApplicationPrivate::processMouseEvent(QWindowSystemInterfacePrivate::MouseEvent*) + 1779
62 0x7fcfc5ee5c08 QCoreApplication::notifyInternal2(QObject*, QEvent*) + 264
61 0x7fcfc79dff01 QApplication::notify(QObject*, QEvent*) + 577
60 0x7fcfc79d8c8c QApplicationPrivate::notify_helper(QObject*, QEvent*) + 156
59 0x7fcfc7a31cd3 /media/store/krs/tools/ParaView-5.8.0-MPI-Linux-Python3.7-64bit/bin/../lib/libQt5Widgets.so.5(+0x1b8cd3) [0x7fcfc7a31cd3]
58 0x7fcfc7a2f42d /media/store/krs/tools/ParaView-5.8.0-MPI-Linux-Python3.7-64bit/bin/../lib/libQt5Widgets.so.5(+0x1b642d) [0x7fcfc7a2f42d]
57 0x7fcfc79df4ed QApplicationPrivate::sendMouseEvent(QWidget*, QMouseEvent*, QWidget*, QWidget*, QWidget**, QPointer<QWidget>&, bool) + 461
56 0x7fcfc5ee5c08 QCoreApplication::notifyInternal2(QObject*, QEvent*) + 264
55 0x7fcfc79e0c78 QApplication::notify(QObject*, QEvent*) + 4024
54 0x7fcfc79d8c8c QApplicationPrivate::notify_helper(QObject*, QEvent*) + 156
53 0x7fcfc7a159d8 QWidget::event(QEvent*) + 488
52 0x7fcfc7acc4c5 QAbstractButton::mouseReleaseEvent(QMouseEvent*) + 213
51 0x7fcfc7acc312 /media/store/krs/tools/ParaView-5.8.0-MPI-Linux-Python3.7-64bit/bin/../lib/libQt5Widgets.so.5(+0x253312) [0x7fcfc7acc312]
50 0x7fcfc7acb014 /media/store/krs/tools/ParaView-5.8.0-MPI-Linux-Python3.7-64bit/bin/../lib/libQt5Widgets.so.5(+0x252014) [0x7fcfc7acb014]
49 0x7fcfc7acae02 QAbstractButton::clicked(bool) + 50
48 0x7fcfc5f11c47 QMetaObject::activate(QObject*, int, int, void**) + 1511
47 0x7fcfc7286c93 pqPropertiesPanel::apply() + 627
46 0x7fcfc5f11c47 QMetaObject::activate(QObject*, int, int, void**) + 1511
45 0x7fcfc7f7bc1c pqApplyBehavior::applied(pqPropertiesPanel*) + 892
44 0x7fcfbaee082f vtkSMViewProxy::Update() + 287
43 0x7fcfc51d7b35 vtkPVSessionBase::ExecuteStream(unsigned int, vtkClientServerStream const&, bool) + 53
42 0x7fcfc51d8a7b vtkPVSessionCore::ExecuteStream(unsigned int, vtkClientServerStream const&, bool) + 59
41 0x7fcfc51d8c45 vtkPVSessionCore::ExecuteStreamInternal(vtkClientServerStream const&, bool) + 245
40 0x7fcfc4757dcd vtkClientServerInterpreter::ProcessStream(vtkClientServerStream const&) + 29
39 0x7fcfc4757a9e vtkClientServerInterpreter::ProcessOneMessage(vtkClientServerStream const&, int) + 1198
38 0x7fcfc4756fda vtkClientServerInterpreter::ProcessCommandInvoke(vtkClientServerStream const&, int) + 330
37 0x7fcfc4756ce5 vtkClientServerInterpreter::CallCommandFunction(char const*, vtkObjectBase*, char const*, vtkClientServerStream const&, vtkClientServerStream&) + 325
36 0x7fcfbc2fbec6 vtkPVRenderViewCommand(vtkClientServerInterpreter*, vtkObjectBase*, char const*, vtkClientServerStream const&, vtkClientServerStream&, void*) + 17558
35 0x7fcfbae5898c vtkPVRenderView::Update() + 140
34 0x7fcfbae6cc2b vtkPVView::Update() + 251
33 0x7fcfbae6b092 vtkPVView::CallProcessViewRequest(vtkInformationRequestKey*, vtkInformation*, vtkInformationVector*) + 242
32 0x7fcfbadd4698 vtkGeometryRepresentationWithFaces::ProcessViewRequest(vtkInformationRequestKey*, vtkInformation*, vtkInformation*) + 24
31 0x7fcfbadd2629 vtkGeometryRepresentation::ProcessViewRequest(vtkInformationRequestKey*, vtkInformation*, vtkInformation*) + 25
30 0x7fcfbae1e1a1 vtkPVDataRepresentation::ProcessViewRequest(vtkInformationRequestKey*, vtkInformation*, vtkInformation*) + 225
29 0x7fcfc0880f0f vtkStreamingDemandDrivenPipeline::Update(int, vtkInformationVector*) + 255
28 0x7fcfc0841f8a vtkDemandDrivenPipeline::UpdateData(int) + 138
27 0x7fcfc087f9b1 vtkStreamingDemandDrivenPipeline::ProcessRequest(vtkInformation*, vtkInformationVector**, vtkInformationVector*) + 801
26 0x7fcfc0843457 vtkDemandDrivenPipeline::ProcessRequest(vtkInformation*, vtkInformationVector**, vtkInformationVector*) + 1447
25 0x7fcfc083dab1 vtkCompositeDataPipeline::ExecuteData(vtkInformation*, vtkInformationVector**, vtkInformationVector*) + 257
24 0x7fcfc08408b7 vtkDemandDrivenPipeline::ExecuteData(vtkInformation*, vtkInformationVector**, vtkInformationVector*) + 55
23 0x7fcfc0846320 vtkExecutive::CallAlgorithm(vtkInformation*, int, vtkInformationVector**, vtkInformationVector*) + 64
22 0x7fcfbadd2c1e vtkGeometryRepresentation::RequestData(vtkInformation*, vtkInformationVector**, vtkInformationVector*) + 110
21 0x7fcfc0880f0f vtkStreamingDemandDrivenPipeline::Update(int, vtkInformationVector*) + 255
20 0x7fcfc0841f8a vtkDemandDrivenPipeline::UpdateData(int) + 138
19 0x7fcfc087f9b1 vtkStreamingDemandDrivenPipeline::ProcessRequest(vtkInformation*, vtkInformationVector**, vtkInformationVector*) + 801
18 0x7fcfc0842fb6 vtkDemandDrivenPipeline::ProcessRequest(vtkInformation*, vtkInformationVector**, vtkInformationVector*) + 262
17 0x7fcfc083c82a vtkCompositeDataPipeline::ForwardUpstream(vtkInformation*) + 330
16 0x7fcfc087f9b1 vtkStreamingDemandDrivenPipeline::ProcessRequest(vtkInformation*, vtkInformationVector**, vtkInformationVector*) + 801
15 0x7fcfc0843457 vtkDemandDrivenPipeline::ProcessRequest(vtkInformation*, vtkInformationVector**, vtkInformationVector*) + 1447
14 0x7fcfc083dab1 vtkCompositeDataPipeline::ExecuteData(vtkInformation*, vtkInformationVector**, vtkInformationVector*) + 257
13 0x7fcfc08408b7 vtkDemandDrivenPipeline::ExecuteData(vtkInformation*, vtkInformationVector**, vtkInformationVector*) + 55
12 0x7fcfc0846320 vtkExecutive::CallAlgorithm(vtkInformation*, int, vtkInformationVector**, vtkInformationVector*) + 64
11 0x7fcfbaa2b408 vtkPVGeometryFilter::RequestData(vtkInformation*, vtkInformationVector**, vtkInformationVector*) + 296
10 0x7fcfbaa2a4df vtkPVGeometryFilter::UnstructuredGridExecute(vtkUnstructuredGridBase*, vtkPolyData*, int) + 655
9 0x7fcfc0880f0f vtkStreamingDemandDrivenPipeline::Update(int, vtkInformationVector*) + 255
8 0x7fcfc0841f8a vtkDemandDrivenPipeline::UpdateData(int) + 138
7 0x7fcfc087f9b1 vtkStreamingDemandDrivenPipeline::ProcessRequest(vtkInformation*, vtkInformationVector**, vtkInformationVector*) + 801
6 0x7fcfc0843457 vtkDemandDrivenPipeline::ProcessRequest(vtkInformation*, vtkInformationVector**, vtkInformationVector*) + 1447
5 0x7fcfc083dab1 vtkCompositeDataPipeline::ExecuteData(vtkInformation*, vtkInformationVector**, vtkInformationVector*) + 257
4 0x7fcfc08408b7 vtkDemandDrivenPipeline::ExecuteData(vtkInformation*, vtkInformationVector**, vtkInformationVector*) + 55
3 0x7fcfc0846320 vtkExecutive::CallAlgorithm(vtkInformation*, int, vtkInformationVector**, vtkInformationVector*) + 64
2 0x7fcfb3be4ea2 vtkUnstructuredGridGeometryFilter::RequestData(vtkInformation*, vtkInformationVector**, vtkInformationVector*) + 11026
1 0x7fcfc0508367 vtkUnstructuredGridCellIterator::FetchFaces() + 71
0 0x7fcfc83a5fd0 /lib/x86_64-linux-gnu/libc.so.6(+0x3efd0) [0x7fcfc83a5fd0]
( 24.836s) [paraview] :0 FATL| Signal: SIGSEGV
Segmentation fault (core dumped)

```

---

<div class="post-metadata">

### Author: ![kayarre](https://discourse.vtk.org/user_avatar/discourse.vtk.org/kayarre/32/808_2.png) [@kayarre](https://discourse.vtk.org/u/kayarre)
#### Post date: [July 27, 2020, 7:27pm UTC](https://discourse.vtk.org/t/xmlunstructuredgridwriter-issue-with-time/3853/3 "2020-07-27T19:27:59Z")

</div>

There is a difference between the options  
`writer->SetDataModeToBinary();`  
this gives an error when being read with paraview

```auto
ERROR: In /home/buildslave/dashboards/buildbot/paraview-pvbinsdash-linux-shared-release_superbuild/build/superbuild/paraview/src/VTK/IO/XMLParser/vtkXMLParser.cxx, line 379
vtkXMLDataParser (0x722a7e0): Error parsing XML in stream at line 1669, column 0, byte index 500120070: no element found

ERROR: In /home/buildslave/dashboards/buildbot/paraview-pvbinsdash-linux-shared-release_superbuild/build/superbuild/paraview/src/VTK/IO/XML/vtkXMLReader.cxx, line 510
vtkXMLUnstructuredGridReader (0x6221d50): Error parsing input file. ReadXMLInformation aborting

```

`writer->SetDataModeToAppended();` gives the error above