// Copyright (c) 2022, ETH Zurich and UNC Chapel Hill.
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// Author: Johannes L. Schoenberger (jsch-at-demuc-dot-de)

#ifndef COLMAP_SRC_OPTIM_PROGRESSIVE_SAMPLER_H_
#define COLMAP_SRC_OPTIM_PROGRESSIVE_SAMPLER_H_

#include "optim/sampler.h"

namespace colmap {

// Random sampler for PROSAC (Progressive Sample Consensus), as described in:
//
//    "Matching with PROSAC - Progressive Sample Consensus".
//        Ondrej Chum and Matas, CVPR 2005.
//
// Note that a separate sampler should be instantiated per thread and that the
// data to be sampled from is assumed to be sorted according to the quality
// function in descending order, i.e., higher quality data is closer to the
// front of the list.
class ProgressiveSampler : public Sampler {
 public:
  explicit ProgressiveSampler(const size_t num_samples);

  void Initialize(const size_t total_num_samples) override;

  size_t MaxNumSamples() override;

  std::vector<size_t> Sample() override;

 private:
  const size_t num_samples_;
  size_t total_num_samples_;

  // The number of generated samples, i.e. the number of calls to `Sample`.
  size_t t_;
  size_t n_;

  // Variables defined in equation 3.
  double T_n_;
  double T_n_p_;
};

}  // namespace colmap

#endif  // COLMAP_SRC_OPTIM_PROGRESSIVE_SAMPLER_H_