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//  This code is based on the algorithm presented in the paper:
//  “Parallel Peak Pruning for Scalable SMP Contour Tree Computation.”
//  Hamish Carr, Gunther Weber, Christopher Sewell, and James Ahrens.
//  Proceedings of the IEEE Symposium on Large Data Analysis and Visualization
//  (LDAV), October 2016, Baltimore, Maryland.

#include <vtkm/cont/DataSet.h>
#include <vtkm/cont/DataSetBuilderUniform.h>
#include <vtkm/cont/Initialize.h>

#include <vtkm/filter/scalar_topology/ContourTreeUniform.h>

#include <fstream>
#include <vector>

// Compute and render an isosurface for a uniform grid example
int main(int argc, char* argv[])
{
  std::cout << "ContourTreeMesh2D Example" << std::endl;

  auto opts = vtkm::cont::InitializeOptions::DefaultAnyDevice;
  vtkm::cont::InitializeResult config = vtkm::cont::Initialize(argc, argv, opts);
  if (argc != 2)
  {
    std::cout << "Usage: "
              << "$ " << argv[0] << " [-d device] input_file" << std::endl;
    std::cout << "File is expected to be ASCII with xdim ydim integers " << std::endl;
    std::cout << "followed by vector data last dimension varying fastest" << std::endl;
    return 0;
  }

  // open input file
  std::ifstream inFile(argv[1]);
  if (inFile.bad())
    return 0;

  // read size of mesh
  vtkm::Id2 vdims;
  inFile >> vdims[0];
  inFile >> vdims[1];
  std::size_t numVertices = static_cast<std::size_t>(vdims[0] * vdims[1]);

  // read data
  std::vector<vtkm::Float32> values(numVertices);
  for (std::size_t vertex = 0; vertex < numVertices; vertex++)
  {
    inFile >> values[vertex];
  }
  inFile.close();

  // build the input dataset
  vtkm::cont::DataSetBuilderUniform dsb;
  vtkm::cont::DataSet inDataSet = dsb.Create(vdims);

  inDataSet.AddPointField("values", values);

  // Convert 2D mesh of values into contour tree, pairs of vertex ids
  vtkm::filter::scalar_topology::ContourTreeMesh2D filter;
  filter.SetActiveField("values");
  // Output data set is pairs of saddle and peak vertex IDs
  vtkm::cont::DataSet output = filter.Execute(inDataSet);
  vtkm::cont::Field resultField = output.GetField("saddlePeak");
  ;
  vtkm::cont::ArrayHandle<vtkm::Pair<vtkm::Id, vtkm::Id>> saddlePeak;
  resultField.GetData().AsArrayHandle(saddlePeak);

  return 0;
}
