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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.

#ifndef vtkm_worklet_contourtree_degree_subrange_offset_h
#define vtkm_worklet_contourtree_degree_subrange_offset_h

#include <vtkm/worklet/WorkletMapField.h>
#include <vtkm/worklet/contourtree/Types.h>

namespace vtkm
{
namespace worklet
{
namespace contourtree
{

// Worklet
class DegreeSubrangeOffset : public vtkm::worklet::WorkletMapField
{
public:
  using ControlSignature = void(FieldIn<IdType> sortID,          // (input) index into sort vector
                                WholeArrayIn<IdType> sortVector, // (input)
                                WholeArrayOut<IdType> degree);   // (output)
  using ExecutionSignature = void(_1, _2, _3);
  using InputDomain = _1;

  // Constructor
  VTKM_EXEC_CONT
  DegreeSubrangeOffset() {}

  template <typename InFieldPortalType, typename OutFieldPortalType>
  VTKM_EXEC void operator()(const vtkm::Id& sortID,
                            const InFieldPortalType& sortVector,
                            const OutFieldPortalType& degree) const
  {
    vtkm::Id superID = sortVector.Get(sortID);
    vtkm::Id prevSuper = sortVector.Get(sortID - 1);

    // if they don't match, we've found a boundary
    if (superID != prevSuper)
      degree.Set(superID, sortID);
  }
}; // DegreeSubrangeOffset
}
}
}

#endif
