//============================================================================
//  The contents of this file are covered by the Viskores license. See
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//
//  By contributing to this file, all contributors agree to the Developer
//  Certificate of Origin Version 1.1 (DCO 1.1) as stated in DCO.txt.
//============================================================================

//============================================================================
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//============================================================================
//  Copyright (c) 2016, Los Alamos National Security, LLC
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//
//  Copyright 2016. Los Alamos National Security, LLC.
//  This software was produced under U.S. Government contract DE-AC52-06NA25396
//  for Los Alamos National Laboratory (LANL), which is operated by
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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 viskores_worklet_contourtree_degree_delta_h
#define viskores_worklet_contourtree_degree_delta_h

#include <viskores/worklet/WorkletMapField.h>

namespace viskores
{
namespace worklet
{
namespace contourtree
{

// Worklet for doing regular to candidate
class DegreeDelta : public viskores::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;

  viskores::Id nCandidates;

  // Constructor
  VISKORES_EXEC_CONT
  DegreeDelta(viskores::Id NCandidates)
    : nCandidates(NCandidates)
  {
  }

  template <typename InFieldPortalType, typename OutFieldPortalType>
  VISKORES_EXEC void operator()(const viskores::Id& sortID,
                                const InFieldPortalType& sortVector,
                                const OutFieldPortalType& candidate) const
  {
    viskores::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
      viskores::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
