PiecewiseLinearFunction.h

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//============================================================================
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//  See LICENSE.txt for details.
//
//  This software is distributed WITHOUT ANY WARRANTY; without even
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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_augmented_process_contourtree_inc_piecewise_linear_function_h
#define vtk_m_worklet_contourtree_augmented_process_contourtree_inc_piecewise_linear_function_h
 
#include <vtkm/Pair.h>
#include <vtkm/cont/ArrayHandle.h>
#include <vtkm/filter/scalar_topology/worklet/contourtree_augmented/ContourTree.h>
 
namespace vtkm
{
namespace worklet
{
namespace contourtree_augmented
{
namespace process_contourtree_inc
{
 
 
template <typename T>
struct PairComparator
{ // PairComparator()
  inline bool operator()(const std::pair<T, T>& s1, const std::pair<T, T>& s2) const
  {
    return s1.second > s2.second;
  }
}; // PairComparator()
 
 
// TODO Need to change the samples to use VTKM data structures instead of std::vector
template <typename T>
class PiecewiseLinearFunction
{
  std::vector<std::pair<T, T>> samples;
 
public:
  void addSample(T sx, T sy)
  {
    auto it = std::find_if_not(
      samples.begin(), samples.end(), [sx](std::pair<T, T> s) { return sx > s.first; });
    samples.insert(it, std::pair<T, T>(sx, sy));
  }
 
  T operator()(T px) const
  {
    if (samples.size() < 2)
      return 0;
    else if (px < samples.front().first || px > samples.back().first)
      return 0;
    else
    {
      auto end = std::find_if_not(
        samples.begin(), samples.end(), [px](std::pair<T, T> s) { return px > s.first; });
      if (end == samples.begin())
      {
        std::cerr << "WARNING!" << std::endl;
        return 0;
      }
      else
      {
        auto begin = end - 1;
        T t = (px - begin->first) / (end->first - begin->first);
        return (1 - t) * begin->second + t * end->second;
      }
    }
  }
 
  PiecewiseLinearFunction& operator+=(const PiecewiseLinearFunction& other)
  {
    std::vector<std::pair<T, T>> new_samples;
    auto it1 = samples.begin();
    auto it2 = other.samples.begin();
 
    while (it1 != samples.end() && it2 != other.samples.end())
    {
      if (it1->first < it2->first)
      {
        new_samples.emplace_back(it1->first, it1->second + other(it1->first));
        ++it1;
      }
      else if (it2->first < it1->first)
      {
        new_samples.emplace_back(it2->first, it2->second + (*this)(it2->first));
        ++it2;
      }
      else
      {
        new_samples.emplace_back(it1->first, it1->second + it2->second);
        ++it1;
        ++it2;
      }
    }
    while (it1 != samples.end())
    {
      new_samples.push_back(*it1);
      ++it1;
    }
    while (it2 != other.samples.end())
    {
      new_samples.push_back(*it2);
      ++it2;
    }
 
    samples.swap(new_samples);
    return *this;
  }
 
  std::vector<T> nLargest(unsigned n)
  {
    std::vector<std::pair<T, T>> sCopy = samples;
    std::sort(sCopy.begin(), sCopy.end(), PairComparator<T>());
    std::vector<T> res;
    for (unsigned i = 0; i < n; ++i)
    {
      res.push_back(sCopy[i].first);
    }
    return res;
  }
 
  void print()
  {
    for (auto sample : samples)
      std::cout << "(" << sample.first << ", " << sample.second << ") ";
    std::cout << std::endl;
  }
};
 
 
 
} // process_contourtree_inc
} // namespace contourtree_augmented
} // namespace worklet
} // namespace vtkm
 
#endif