sprt.h

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// ----------------------------------------------------------------------------
// -                        CloudViewer: www.cloudViewer.org                  -
// ----------------------------------------------------------------------------
// Copyright (c) 2018-2024 www.cloudViewer.org
// SPDX-License-Identifier: MIT
// ----------------------------------------------------------------------------
 
#pragma once
 
#include <cmath>
#include <cstddef>
#include <vector>
 
namespace colmap {
 
// Sequential Probability Ratio Test as proposed in
//
//   "Randomized RANSAC with Sequential Probability Ratio Test",
//   Matas et al., 2005
class SPRT {
public:
    struct Options {
        // Probability of rejecting a good model.
        double delta = 0.01;
 
        // A priori assumed minimum inlier ratio
        double epsilon = 0.1;
 
        // The ratio of the time it takes to estimate a model from a random
        // sample over the time it takes to decide whether one data sample is an
        // inlier or not. Matas et al. propose 200 for the 7-point algorithm.
        double eval_time_ratio = 200;
 
        // Number of models per random sample, that have to be verified. E.g.
        // 1-3 for the 7-point fundamental matrix algorithm, or 1-10 for the
        // 5-point essential matrix algorithm.
        int num_models_per_sample = 1;
    };
 
    explicit SPRT(const Options& options);
 
    void Update(const Options& options);
 
    bool Evaluate(const std::vector<double>& residuals,
                  const double max_residual,
                  size_t* num_inliers,
                  size_t* num_eval_samples);
 
private:
    void UpdateDecisionThreshold();
 
    Options options_;
    double delta_epsilon_;
    double delta_1_epsilon_1_;
    double decision_threshold_;
};
 
}  // namespace colmap