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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_regular_to_critical_down_h
#define vtkm_worklet_contourtree_regular_to_critical_down_h

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

namespace vtkm
{
namespace worklet
{
namespace contourtree
{

// Worklet for doing regular to critical
class RegularToCriticalDown : public vtkm::worklet::WorkletMapField
{
public:
  using ControlSignature = void(FieldIn vertexID,               // (input) candidate index
                                WholeArrayIn mergeArcs,         // (input) merge arcs
                                WholeArrayIn regularToCritical, // (input)
                                FieldOut sortVector);           // (output)
  using ExecutionSignature = _4(_1, _2, _3);
  using InputDomain = _1;

  // Constructor
  VTKM_EXEC_CONT
  RegularToCriticalDown() {}

  template <typename InFieldPortalType>
  VTKM_EXEC vtkm::Id operator()(const vtkm::Id& vertexID,
                                const InFieldPortalType& mergeArcs,
                                const InFieldPortalType& regularToCritical) const
  {
    vtkm::Id sortVector;

    // copy the mergeArc ID
    vtkm::Id splitNeighbour = mergeArcs.Get(vertexID);
    // if it's the root vertex
    if (splitNeighbour == NO_VERTEX_ASSIGNED)
      // set it to the sentinel value
      sortVector = NO_VERTEX_ASSIGNED;
    else
      // otherwise convert to a candidate ID & save
      sortVector = regularToCritical.Get(splitNeighbour);
    return sortVector;
  }
}; // RegularToCriticalDown
}
}
}

#endif
