ransac.hpp

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#ifndef PCL_SAMPLE_CONSENSUS_IMPL_RANSAC_H_
#define PCL_SAMPLE_CONSENSUS_IMPL_RANSAC_H_
 
#include <pcl/sample_consensus/ransac.h>
#ifdef _OPENMP
#include <omp.h>
#endif
 
#if defined _OPENMP && _OPENMP >= 201107 // We need OpenMP 3.1 for the atomic constructs
#define OPENMP_AVAILABLE_RANSAC true
#else
#define OPENMP_AVAILABLE_RANSAC false
#endif
 
//////////////////////////////////////////////////////////////////////////
template <typename PointT> bool
pcl::RandomSampleConsensus<PointT>::computeModel (int)
{
  // Warn and exit if no threshold was set
  if (threshold_ == std::numeric_limits<double>::max())
  {
    PCL_ERROR ("[pcl::RandomSampleConsensus::computeModel] No threshold set!\n");
    return (false);
  }
 
  iterations_ = 0;
  std::size_t n_best_inliers_count = 0;
  double k = std::numeric_limits<double>::max();
 
  Indices selection;
  Eigen::VectorXf model_coefficients (sac_model_->getModelSize ());
 
  const double log_probability  = std::log (1.0 - probability_);
  const double one_over_indices = 1.0 / static_cast<double> (sac_model_->getIndices ()->size ());
 
  unsigned skipped_count = 0;
 
  // suppress infinite loops by just allowing 10 x maximum allowed iterations for invalid model parameters!
  const unsigned max_skip = max_iterations_ * 10;
 
  int threads = threads_;
  if (threads >= 0)
  {
#if OPENMP_AVAILABLE_RANSAC
    if (threads == 0)
    {
      threads = omp_get_num_procs();
      PCL_DEBUG ("[pcl::RandomSampleConsensus::computeModel] Automatic number of threads requested, choosing %i threads.\n", threads);
    }
#else
    // Parallelization desired, but not available
    PCL_WARN ("[pcl::RandomSampleConsensus::computeModel] Parallelization is requested, but OpenMP 3.1 is not available! Continuing without parallelization.\n");
    threads = -1;
#endif
  }
 
#if OPENMP_AVAILABLE_RANSAC
#pragma omp parallel if(threads > 0) num_threads(threads) shared(k, skipped_count, n_best_inliers_count) firstprivate(selection, model_coefficients) // would be nice to have a default(none)-clause here, but then some compilers complain about the shared const variables
#endif
  {
#if OPENMP_AVAILABLE_RANSAC
    if (omp_in_parallel())
#pragma omp master
      PCL_DEBUG ("[pcl::RandomSampleConsensus::computeModel] Computing in parallel with up to %i threads.\n", omp_get_num_threads());
    else
#endif
      PCL_DEBUG ("[pcl::RandomSampleConsensus::computeModel] Computing not parallel.\n");
 
    // Iterate
    while (true) // infinite loop with four possible breaks
    {
      // Get X samples which satisfy the model criteria
#if OPENMP_AVAILABLE_RANSAC
#pragma omp critical(samples)
#endif
      {
        sac_model_->getSamples (iterations_, selection); // The random number generator used when choosing the samples should not be called in parallel
      }
 
      if (selection.empty ())
      {
        PCL_ERROR ("[pcl::RandomSampleConsensus::computeModel] No samples could be selected!\n");
        break;
      }
 
      // Search for inliers in the point cloud for the current plane model M
      if (!sac_model_->computeModelCoefficients (selection, model_coefficients)) // This function has to be thread-safe
      {
        //++iterations_;
        unsigned skipped_count_tmp;
#if OPENMP_AVAILABLE_RANSAC
#pragma omp atomic capture
#endif
        skipped_count_tmp = ++skipped_count;
        if (skipped_count_tmp < max_skip)
          continue;
        else
          break;
      }
 
      // Select the inliers that are within threshold_ from the model
      //sac_model_->selectWithinDistance (model_coefficients, threshold_, inliers);
      //if (inliers.empty () && k > 1.0)
      //  continue;
 
      std::size_t n_inliers_count = sac_model_->countWithinDistance (model_coefficients, threshold_); // This functions has to be thread-safe. Most work is done here
 
      std::size_t n_best_inliers_count_tmp;
#if OPENMP_AVAILABLE_RANSAC
#pragma omp atomic read
#endif
      n_best_inliers_count_tmp = n_best_inliers_count;
 
      if (n_inliers_count > n_best_inliers_count_tmp) // This condition is false most of the time, and the critical region is not entered, hopefully leading to more efficient concurrency
      {
#if OPENMP_AVAILABLE_RANSAC
#pragma omp critical(update) // n_best_inliers_count, model_, model_coefficients_, k are shared and read/write must be protected
#endif
        {
          // Better match ?
          if (n_inliers_count > n_best_inliers_count)
          {
            n_best_inliers_count = n_inliers_count; // This write and the previous read of n_best_inliers_count must be consecutive and must not be interrupted!
            n_best_inliers_count_tmp = n_best_inliers_count;
 
            // Save the current model/inlier/coefficients selection as being the best so far
            model_              = selection;
            model_coefficients_ = model_coefficients;
 
            // Compute the k parameter (k=std::log(z)/std::log(1-w^n))
            const double w = static_cast<double> (n_best_inliers_count) * one_over_indices;
            double p_outliers = 1.0 - std::pow (w, static_cast<double> (selection.size ()));      // Probability that selection is contaminated by at least one outlier
            p_outliers = (std::max) (std::numeric_limits<double>::epsilon (), p_outliers);        // Avoid division by -Inf
            p_outliers = (std::min) (1.0 - std::numeric_limits<double>::epsilon (), p_outliers);  // Avoid division by 0.
            k = log_probability / std::log (p_outliers);
          }
        } // omp critical
      }
 
      int iterations_tmp;
      double k_tmp;
#if OPENMP_AVAILABLE_RANSAC
#pragma omp atomic capture
#endif
      iterations_tmp = ++iterations_;
#if OPENMP_AVAILABLE_RANSAC
#pragma omp atomic read
#endif
      k_tmp = k;
#if OPENMP_AVAILABLE_RANSAC
      PCL_DEBUG ("[pcl::RandomSampleConsensus::computeModel] Trial %d out of %f: %u inliers (best is: %u so far) (thread %d).\n", iterations_tmp, k_tmp, n_inliers_count, n_best_inliers_count_tmp, omp_get_thread_num());
#else
      PCL_DEBUG ("[pcl::RandomSampleConsensus::computeModel] Trial %d out of %f: %u inliers (best is: %u so far).\n", iterations_tmp, k_tmp, n_inliers_count, n_best_inliers_count_tmp);
#endif
      if (iterations_tmp > k_tmp)
        break;
      if (iterations_tmp > max_iterations_)
      {
        PCL_DEBUG ("[pcl::RandomSampleConsensus::computeModel] RANSAC reached the maximum number of trials.\n");
        break;
      }
    } // while
  } // omp parallel
 
  PCL_DEBUG ("[pcl::RandomSampleConsensus::computeModel] Model: %lu size, %u inliers.\n", model_.size (), n_best_inliers_count);
 
  if (model_.empty ())
  {
    PCL_ERROR ("[pcl::RandomSampleConsensus::computeModel] RANSAC found no model.\n");
    inliers_.clear ();
    return (false);
  }
 
  // Get the set of inliers that correspond to the best model found so far
  sac_model_->selectWithinDistance (model_coefficients_, threshold_, inliers_);
  return (true);
}
 
#define PCL_INSTANTIATE_RandomSampleConsensus(T) template class PCL_EXPORTS pcl::RandomSampleConsensus<T>;
 
#endif    // PCL_SAMPLE_CONSENSUS_IMPL_RANSAC_H_