random_rejection_filter.hpp

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/* Copyright (c) 2025 Otto Link. Distributed under the terms of the GNU General
   Public License. The full license is in the file LICENSE, distributed with
   this software. */
#pragma once
 
#include "point_sampler/internal/nanoflann_adaptator.hpp"
#include "point_sampler/point.hpp"
 
#include <iostream>
 
namespace ps
{
 
template <typename T, std::size_t N>
std::vector<Point<T, N>> random_rejection_filter(const std::vector<Point<T, N>> &points,
                                                 std::size_t target_count)
{
  if (target_count >= points.size())
  {
    return points; // nothing to remove
  }
 
  std::vector<std::size_t> indices(points.size());
  std::iota(indices.begin(), indices.end(), 0);
 
  std::random_device rd;
  std::mt19937       gen(rd());
  std::shuffle(indices.begin(), indices.end(), gen);
 
  // Take the first `target_count` shuffled indices
  std::vector<Point<T, N>> result;
  result.reserve(target_count);
  for (std::size_t i = 0; i < target_count; ++i)
  {
    result.push_back(points[indices[i]]);
  }
 
  return result;
}
 
template <typename T, std::size_t N>
std::vector<Point<T, N>> random_rejection_filter(const std::vector<Point<T, N>> &points,
                                                 float keep_fraction)
{
  assert(keep_fraction >= 0.0 && keep_fraction <= 1.0);
  std::size_t target_count = static_cast<std::size_t>(keep_fraction * points.size());
  return random_rejection_filter(points, target_count);
}
 
} // namespace ps