text: //============================================================================
  //  Copyright (c) Kitware, Inc.
  //  All rights reserved.
  //  See LICENSE.txt for details.
  //
  //  This software is distributed WITHOUT ANY WARRANTY; without even
  //  the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
  //  PURPOSE.  See the above copyright notice for more information.
  //============================================================================
  // Copyright (c) 2018, The Regents of the University of California, through
  // Lawrence Berkeley National Laboratory (subject to receipt of any required approvals
  // from the U.S. Dept. of Energy).  All rights reserved.
  //
  // Redistribution and use in source and binary forms, with or without modification,
  // are permitted provided that the following conditions are met:
  //
  // (1) Redistributions of source code must retain the above copyright notice, this
  //     list of conditions and the following disclaimer.
  //
  // (2) Redistributions in binary form must reproduce the above copyright notice,
  //     this list of conditions and the following disclaimer in the documentation
  //     and/or other materials provided with the distribution.
  //
  // (3) Neither the name of the University of California, Lawrence Berkeley National
  //     Laboratory, U.S. Dept. of Energy nor the names of its contributors may be
  //     used to endorse or promote products derived from this software without
  //     specific prior written permission.
  //
  // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
  // ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  // WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  // IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
  // INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
  // BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
  // LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
  // OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
  // OF THE POSSIBILITY OF SUCH DAMAGE.
  //
  //=============================================================================
  //
  //  This code is an extension of 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.
  //
  //  The PPP2 algorithm and software were jointly developed by
  //  Hamish Carr (University of Leeds), Gunther H. Weber (LBNL), and
  //  Oliver Ruebel (LBNL)
  //==============================================================================
  
  #ifndef vtk_m_worklet_contourtree_augmented_process_contourtree_inc_supernode_branch_comperator_h
  #define vtk_m_worklet_contourtree_augmented_process_contourtree_inc_supernode_branch_comperator_h
  
  #include <vtkm/Pair.h>
  #include <vtkm/Types.h>
  #include <vtkm/cont/ArrayHandle.h>
  #include <vtkm/cont/ExecutionObjectBase.h>
  #include <vtkm/worklet/contourtree_augmented/Types.h>
  
  namespace vtkm
  {
  namespace worklet
  {
  namespace contourtree_augmented
  {
  namespace process_contourtree_inc
  {
  
  template <typename DeviceAdapter>
  class SuperNodeBranchComparatorImpl
  { // SuperNodeBranchComparatorImpl
  public:
    using IdPortalType =
      typename vtkm::cont::ArrayHandle<vtkm::Id>::template ExecutionTypes<DeviceAdapter>::PortalConst;
    IdPortalType WhichBranchPortal;
    IdPortalType SupernodesPortal;
  
    // constructor
    SuperNodeBranchComparatorImpl(const IdArrayType& whichBranch,
                                  const IdArrayType& supernodes,
                                  vtkm::cont::Token& token)
    { // constructor
      this->WhichBranchPortal = whichBranch.PrepareForInput(DeviceAdapter(), token);
      this->SupernodesPortal = supernodes.PrepareForInput(DeviceAdapter(), token);
    } // constructor
  
    // () operator - gets called to do comparison
    VTKM_EXEC
    bool operator()(const vtkm::Id& i, const vtkm::Id& j) const
    { // operator()
      // retrieve which branch the supernodes are on
      vtkm::Id branchI = MaskedIndex(this->WhichBranchPortal.Get(i));
      vtkm::Id branchJ = MaskedIndex(this->WhichBranchPortal.Get(j));
  
      // and test them
      if (branchI < branchJ)
        return true;
      if (branchJ < branchI)
        return false;
  
      // now fall back on regular ID
      vtkm::Id regularI = this->SupernodesPortal.Get(i);
      vtkm::Id regularJ = this->SupernodesPortal.Get(j);
  
      if (regularI < regularJ)
        return true;
      if (regularJ < regularI)
        return false;
  
      // fallback just in case
      return false;
    } // operator()
  };  // SuperNodeBranchComparatorImpl
  
  class SuperNodeBranchComparator : public vtkm::cont::ExecutionObjectBase
  { // SuperNodeBranchComparator
  public:
    // constructor
    SuperNodeBranchComparator(const IdArrayType& whichBranch, const IdArrayType& supernodes)
      : WhichBranch(whichBranch)
      , Supernodes(supernodes)
    {
    }
  
    template <typename DeviceAdapter>
    VTKM_CONT SuperNodeBranchComparatorImpl<DeviceAdapter> PrepareForExecution(
      DeviceAdapter,
      vtkm::cont::Token& token)
    {
      return SuperNodeBranchComparatorImpl<DeviceAdapter>(this->WhichBranch, this->Supernodes, token);
    }
  
  private:
    IdArrayType WhichBranch;
    IdArrayType Supernodes;
  }; // SuperNodeBranchComparator
  
  
  } // namespace process_contourtree_inc
  } // namespace contourtree_augmented
  } // namespace worklet
  } // namespace vtkm
  
  #endif
  