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

#ifndef COLMAP_SRC_OPTIM_SUPPORT_MEASUREMENT_H_
#define COLMAP_SRC_OPTIM_SUPPORT_MEASUREMENT_H_

#include <cstddef>
#include <limits>
#include <vector>

namespace colmap {

// Measure the support of a model by counting the number of inliers and
// summing all inlier residuals. The support is better if it has more inliers
// and a smaller residual sum.
struct InlierSupportMeasurer {
  struct Support {
    // The number of inliers.
    size_t num_inliers = 0;

    // The sum of all inlier residuals.
    double residual_sum = std::numeric_limits<double>::max();
  };

  // Compute the support of the residuals.
  Support Evaluate(const std::vector<double>& residuals,
                   const double max_residual);

  // Compare the two supports and return the better support.
  bool Compare(const Support& support1, const Support& support2);
};

// Measure the support of a model by its fitness to the data as used in MSAC.
// A support is better if it has a smaller MSAC score.
struct MEstimatorSupportMeasurer {
  struct Support {
    // The number of inliers.
    size_t num_inliers = 0;

    // The MSAC score, defined as the truncated sum of residuals.
    double score = std::numeric_limits<double>::max();
  };

  // Compute the support of the residuals.
  Support Evaluate(const std::vector<double>& residuals,
                   const double max_residual);

  // Compare the two supports and return the better support.
  bool Compare(const Support& support1, const Support& support2);
};

}  // namespace colmap

#endif  // COLMAP_SRC_OPTIM_SUPPORT_MEASUREMENT_H_