FindRegularByGlobal.h

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//============================================================================
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//
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//  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:
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// (1) Redistributions of source code must retain the above copyright notice, this
//     list of conditions and the following disclaimer.
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//     this list of conditions and the following disclaimer in the documentation
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// (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
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//=============================================================================
//
//  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_distributed_find_regular_by_global_device_data_h
#define vtk_m_worklet_contourtree_distributed_find_regular_by_global_device_data_h
 
#include <vtkm/Types.h>
#include <vtkm/filter/scalar_topology/worklet/contourtree_augmented/Types.h>
 
 
namespace vtkm
{
namespace worklet
{
namespace contourtree_distributed
{
 
 
class FindRegularByGlobalDeviceData
{
public:
  using IndicesPortalType =
    typename vtkm::worklet::contourtree_augmented::IdArrayType::ReadPortalType;
 
  VTKM_CONT
  FindRegularByGlobalDeviceData(
    vtkm::cont::DeviceAdapterId device,
    vtkm::cont::Token& token,
    const vtkm::worklet::contourtree_augmented::IdArrayType& regularNodeSortOrder,
    const vtkm::worklet::contourtree_augmented::IdArrayType& regularNodeGlobalIds)
  {
    // Prepare the arrays for input and store the array portals
    // so that they can be used inside a workelt
    this->RegularNodeSortOrder = regularNodeSortOrder.PrepareForInput(device, token);
    this->RegularNodeGlobalIds = regularNodeGlobalIds.PrepareForInput(device, token);
  }
 
  VTKM_EXEC
  vtkm::Id operator()(vtkm::Id globalId) const { return this->FindRegularByGlobal(globalId); }
 
  // TODO: This is just a binary search. Does VTKm have an implementation we can use to replace this with?
  VTKM_EXEC
  vtkm::Id FindRegularByGlobal(vtkm::Id globalId) const
  { // FindRegularByGlobal()
    // this is just a binary search, but the C++ STL doesn't seem to implement it . . .
    vtkm::Id left = 0;
    vtkm::Id right = this->RegularNodeSortOrder.GetNumberOfValues() - 1;
 
    // pull LHE into register & check whether target is in range
    vtkm::Id leftId = this->RegularNodeGlobalIds.Get(this->RegularNodeSortOrder.Get(left));
    if (leftId > globalId)
    {
      return vtkm::worklet::contourtree_augmented::NO_SUCH_ELEMENT;
    }
 
    // exact match on the left
    if (leftId == globalId)
    {
      return this->RegularNodeSortOrder.Get(left);
    }
 
    // pull RHE into register & check whether target is in range
    vtkm::Id rightId = this->RegularNodeGlobalIds.Get(this->RegularNodeSortOrder.Get(right));
    // RHE is less than target, so not present
    if (rightId < globalId)
    {
      return vtkm::worklet::contourtree_augmented::NO_SUCH_ELEMENT;
    }
 
    // exact match on the right
    if (rightId == globalId)
    {
      return this->RegularNodeSortOrder.Get(right);
    }
 
    // loop until the two meet
    while (left <= right)
    { // while loop
 
      // compute the midpoint
      vtkm::Id mid = (left + right) / 2;
      vtkm::Id midId = this->RegularNodeGlobalIds.Get(this->RegularNodeSortOrder.Get(mid));
 
      // compare with the value
      if (midId == globalId)
      { // exact match
        return this->RegularNodeSortOrder.Get(mid);
      } // exact match
 
      if (midId < globalId)
      { // mid is lower: global is in right half
        left = mid + 1;
        leftId = this->RegularNodeGlobalIds.Get(this->RegularNodeSortOrder.Get(left));
      } // mid is lower: global is in right half
 
      if (midId > globalId)
      { // mid is higher: global is in left half
        right = mid - 1;
        rightId = this->RegularNodeGlobalIds.Get(this->RegularNodeSortOrder.Get(right));
      } // mid is higher: global is in left half
    }   // while loop
 
    // if we fell through, we didn't find it
    return vtkm::worklet::contourtree_augmented::NO_SUCH_ELEMENT;
  } // FindRegularByGlobal()
 
private:
  // Array portals needed by FindRegularByGlobal
  IndicesPortalType RegularNodeSortOrder;
  IndicesPortalType RegularNodeGlobalIds;
};
 
 
class FindRegularByGlobal : public vtkm::cont::ExecutionObjectBase
{
public:
  VTKM_CONT
  FindRegularByGlobal(const vtkm::worklet::contourtree_augmented::IdArrayType& regularNodeSortOrder,
                      const vtkm::worklet::contourtree_augmented::IdArrayType& regularNodeGlobalIds)
    : RegularNodeSortOrder(regularNodeSortOrder)
    , RegularNodeGlobalIds(regularNodeGlobalIds)
  {
  }
 
  VTKM_CONT FindRegularByGlobalDeviceData PrepareForExecution(vtkm::cont::DeviceAdapterId device,
                                                              vtkm::cont::Token& token) const
  {
    return FindRegularByGlobalDeviceData(
      device, token, this->RegularNodeSortOrder, this->RegularNodeGlobalIds);
  }
 
private:
  // Array portals needed by FindRegularByGlobal
  vtkm::worklet::contourtree_augmented::IdArrayType RegularNodeSortOrder;
  vtkm::worklet::contourtree_augmented::IdArrayType RegularNodeGlobalIds;
};
 
 
} // namespace contourtree_distributed
} // namespace worklet
} // namespace vtkm
 
#endif