SaddleAscentTransferrer.h

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//============================================================================
//  Copyright (c) 2016, Los Alamos National Security, LLC
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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.
 
//=======================================================================================
//
// COMMENTS:
//
// Any vector needed by the functor for lookup purposes will be passed as a parameter to
// the constructor and saved, with the actual function call being the operator ()
//
// Vectors marked I/O are intrinsically risky unless there is an algorithmic guarantee
// that the read/writes are completely independent - which for our case actually occurs
// The I/O vectors should therefore be justified in comments both here & in caller
//
//=======================================================================================
 
#ifndef vtkm_worklet_contourtree_saddle_ascent_transferrer_h
#define vtkm_worklet_contourtree_saddle_ascent_transferrer_h
 
#include <vtkm/worklet/WorkletMapField.h>
 
namespace vtkm
{
namespace worklet
{
namespace contourtree
{
 
// Worklet for setting initial chain maximum value
class SaddleAscentTransferrer : public vtkm::worklet::WorkletMapField
{
public:
  using ControlSignature = void(FieldIn vertexID,          // (input) active vertex
                                FieldIn newOutdegree,      // (input) updated updegree
                                FieldIn newFirstEdge,      // (input) updated first edge of vertex
                                WholeArrayIn activeEdges,  // (input) active edges
                                WholeArrayIn firstEdge,    // (input) first edges
                                WholeArrayOut edgeSorter); // (output) edge sorter
  using ExecutionSignature = void(_1, _2, _3, _4, _5, _6);
  using InputDomain = _1;
 
  // Constructor
  VTKM_EXEC_CONT
  SaddleAscentTransferrer() {}
 
  template <typename InFieldPortalType, typename OutFieldPortalType>
  VTKM_EXEC void operator()(const vtkm::Id& vertexID,
                            const vtkm::Id& newOutdegree,
                            const vtkm::Id& newFirstEdge,
                            const InFieldPortalType& activeEdges,
                            const InFieldPortalType& firstEdge,
                            const OutFieldPortalType& edgeSorter) const
  {
    // loop through the edges from the vertex
    for (vtkm::Id edge = 0; edge < newOutdegree; edge++)
    {
      // compute which index in the new sorting array
      vtkm::Id edgeSorterIndex = newFirstEdge + edge;
      // now retrieve the old edge
      vtkm::Id edgeID = activeEdges.Get(firstEdge.Get(vertexID) + edge);
      // adding them to the edge sort array
      edgeSorter.Set(edgeSorterIndex, edgeID);
    }
  }
 
}; // SaddleAscentTransferrer
}
}
}
 
#endif