DegreeDelta.h

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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_delta_h
#define vtkm_worklet_contourtree_degree_delta_h
 
#include <vtkm/worklet/WorkletMapField.h>
 
namespace vtkm
{
namespace worklet
{
namespace contourtree
{
 
// Worklet for doing regular to candidate
class DegreeDelta : public vtkm::worklet::WorkletMapField
{
public:
  using ControlSignature = void(FieldIn sortID, // (input) index into sorted vertices [1..N]
                                WholeArrayIn sortVector,  // (input) sorted vector of vertices
                                WholeArrayOut candidate); // (output) candidate
  using ExecutionSignature = void(_1, _2, _3);
  using InputDomain = _1;
 
  vtkm::Id nCandidates;
 
  // Constructor
  VTKM_EXEC_CONT
  DegreeDelta(vtkm::Id NCandidates)
    : nCandidates(NCandidates)
  {
  }
 
  template <typename InFieldPortalType, typename OutFieldPortalType>
  VTKM_EXEC void operator()(const vtkm::Id& sortID,
                            const InFieldPortalType& sortVector,
                            const OutFieldPortalType& candidate) const
  {
    vtkm::Id iCandidate = sortVector.Get(sortID);
    // last element needs to be subtracted from vector size
    if (sortID == nCandidates - 1)
    { // final element
      candidate.Set(iCandidate, (nCandidates - candidate.Get(iCandidate)));
    } // final element
    // otherwise, if the next one is different
    else
    { // not the last element
      vtkm::Id nextCandidate = sortVector.Get(sortID + 1);
      if (iCandidate != nextCandidate)
      { // no match
        candidate.Set(iCandidate, (sortID + 1 - candidate.Get(iCandidate)));
      } // no match
    }   // not the last element
  }
}; // DegreeDelta
}
}
}
 
#endif