JoinTreeTransferrer.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:
//
// This functor identifies for each vertex which edges to keep. For arbitrary meshes,
// this should use reductions. For regular meshes, this way is faster due to low bounded
// updegree.
//
// 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_join_tree_transferrer_h
#define vtkm_worklet_contourtree_join_tree_transferrer_h
 
#include <vtkm/filter/scalar_topology/worklet/contourtree/Types.h>
#include <vtkm/worklet/WorkletMapField.h>
 
namespace vtkm
{
namespace worklet
{
namespace contourtree
{
 
// Worklet for setting initial chain maximum value
class JoinTreeTransferrer : public vtkm::worklet::WorkletMapField
{
public:
  using ControlSignature = void(FieldIn vertex,            // (input) index into active vertices
                                FieldIn prunesTo,          // (input) where vertex is pruned to
                                WholeArrayIn valueIndex,   // (input) indices into main array
                                WholeArrayIn chainExtemum, // (input) chain extemum for vertices
                                WholeArrayOut saddles,     // (output) saddle array for writing
                                WholeArrayOut arcArray);   // (output) arc / max array for writing
  using ExecutionSignature = void(_1, _2, _3, _4, _5, _6);
  using InputDomain = _1;
 
  // Constructor
  VTKM_EXEC_CONT
  JoinTreeTransferrer() {}
 
  template <typename InFieldPortalType, typename OutFieldPortalType>
  VTKM_EXEC void operator()(const vtkm::Id& vertex,
                            const vtkm::Id& prunesTo,
                            const InFieldPortalType& valueIndex,
                            const InFieldPortalType& chainExtremum,
                            const OutFieldPortalType& saddles,
                            const OutFieldPortalType& arcArray) const
  {
    // convert vertex & prunesTo to indices in original data
    // and write to saddle array
    if (prunesTo == NO_VERTEX_ASSIGNED)
      saddles.Set(valueIndex.Get(vertex), NO_VERTEX_ASSIGNED);
    else
      saddles.Set(valueIndex.Get(vertex), valueIndex.Get(prunesTo));
    // and in either event, we need to transfer the chain maximum
    arcArray.Set(valueIndex.Get(vertex), valueIndex.Get(chainExtremum.Get(vertex)));
  }
}; // JoinTreeTransferrer
}
}
}
 
#endif