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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 vtk_m_worklet_ContourTreeUniform_h
#define vtk_m_worklet_ContourTreeUniform_h

#include <vtkm/Math.h>
#include <vtkm/cont/ArrayHandle.h>
#include <vtkm/cont/ArrayHandleCounting.h>
#include <vtkm/cont/Field.h>
#include <vtkm/worklet/DispatcherMapField.h>
#include <vtkm/worklet/WorkletMapField.h>

// For numerous functions inside contourTree GCC is able to determine if i is
// always greater than j ( or vice-versa ) and optimizes those call sites.
// But when it does these optimizations is presumes that i and j will not
// overflow and emits a Wstrict-overflow warning
#ifdef VTKM_GCC
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wstrict-overflow"
#endif

#include <vtkm/worklet/contourtree/ChainGraph.h>
#include <vtkm/worklet/contourtree/ContourTree.h>
#include <vtkm/worklet/contourtree/MergeTree.h>
#include <vtkm/worklet/contourtree/Mesh2D_DEM_Triangulation.h>
#include <vtkm/worklet/contourtree/Mesh3D_DEM_Triangulation.h>

const bool JOIN = true;
const bool SPLIT = false;
const bool JOIN_3D = true;
const bool SPLIT_3D = false;

namespace vtkm
{
namespace worklet
{

class ContourTreeMesh2D
{
public:
  template <typename FieldType, typename StorageType>
  void Run(const vtkm::cont::ArrayHandle<FieldType, StorageType> fieldArray,
           const vtkm::Id nRows,
           const vtkm::Id nCols,
           vtkm::cont::ArrayHandle<vtkm::Pair<vtkm::Id, vtkm::Id>>& saddlePeak)
  {
    vtkm::Id nSlices = 1;

    // Build the mesh and fill in the values
    contourtree::Mesh2D_DEM_Triangulation<FieldType, StorageType> mesh(fieldArray, nRows, nCols);

    // Initialize the join tree so that all arcs point to maxima
    contourtree::MergeTree<FieldType, StorageType> joinTree(
      fieldArray, nRows, nCols, nSlices, JOIN);
    mesh.SetStarts(joinTree.extrema, JOIN);
    joinTree.BuildRegularChains();

    // Create the active topology graph from the regular graph
    contourtree::ChainGraph<FieldType, StorageType> joinGraph(fieldArray, joinTree.extrema, JOIN);
    mesh.SetSaddleStarts(joinGraph, JOIN);

    // Call join graph to finish computation
    joinGraph.Compute(joinTree.saddles);

    // Initialize the split tree so that all arcs point to maxima
    contourtree::MergeTree<FieldType, StorageType> splitTree(
      fieldArray, nRows, nCols, nSlices, SPLIT);
    mesh.SetStarts(splitTree.extrema, SPLIT);
    splitTree.BuildRegularChains();

    // Create the active topology graph from the regular graph
    contourtree::ChainGraph<FieldType, StorageType> splitGraph(
      fieldArray, splitTree.extrema, SPLIT);
    mesh.SetSaddleStarts(splitGraph, SPLIT);

    // Call split graph to finish computation
    splitGraph.Compute(splitTree.saddles);

    // Now compute the contour tree
    contourtree::ContourTree<FieldType, StorageType> contourTree(
      fieldArray, joinTree, splitTree, joinGraph, splitGraph);

    contourTree.CollectSaddlePeak(saddlePeak);
  }
};

class ContourTreeMesh3D
{
public:
  template <typename FieldType, typename StorageType>
  void Run(const vtkm::cont::ArrayHandle<FieldType, StorageType> fieldArray,
           const vtkm::Id nRows,
           const vtkm::Id nCols,
           const vtkm::Id nSlices,
           vtkm::cont::ArrayHandle<vtkm::Pair<vtkm::Id, vtkm::Id>>& saddlePeak)
  {
    // Build the mesh and fill in the values
    contourtree::Mesh3D_DEM_Triangulation<FieldType, StorageType> mesh(
      fieldArray, nRows, nCols, nSlices);

    // Initialize the join tree so that all arcs point to maxima
    contourtree::MergeTree<FieldType, StorageType> joinTree(
      fieldArray, nRows, nCols, nSlices, JOIN_3D);
    mesh.SetStarts(joinTree.extrema, JOIN_3D);
    joinTree.BuildRegularChains();

    // Create the active topology graph from the regular graph
    contourtree::ChainGraph<FieldType, StorageType> joinGraph(
      fieldArray, joinTree.extrema, JOIN_3D);
    mesh.SetSaddleStarts(joinGraph, JOIN_3D);

    // Call join graph to finish computation
    joinGraph.Compute(joinTree.saddles);

    // Initialize the split tree so that all arcs point to maxima
    contourtree::MergeTree<FieldType, StorageType> splitTree(
      fieldArray, nRows, nCols, nSlices, SPLIT_3D);
    mesh.SetStarts(splitTree.extrema, SPLIT_3D);
    splitTree.BuildRegularChains();

    // Create the active topology graph from the regular graph
    contourtree::ChainGraph<FieldType, StorageType> splitGraph(
      fieldArray, splitTree.extrema, SPLIT_3D);
    mesh.SetSaddleStarts(splitGraph, SPLIT_3D);

    // Call split graph to finish computation
    splitGraph.Compute(splitTree.saddles);

    // Now compute the contour tree
    contourtree::ContourTree<FieldType, StorageType> contourTree(
      fieldArray, joinTree, splitTree, joinGraph, splitGraph);

    contourTree.CollectSaddlePeak(saddlePeak);
  }
};
}
} // namespace vtkm::worklet

#ifdef VTKM_GCC
#pragma GCC diagnostic pop
#endif

#endif // vtk_m_worklet_ContourTreeUniform_h