Method Match

src/colmap/feature/sift.cc:1332–1383

  }

  void Match(const Image& image1,
             const Image& image2,
             FeatureMatches* matches) override {
    THROW_CHECK_NOTNULL(matches);
    ThrowCheckFeatureTypesMatch(image1, image2);

    matches->clear();

    // Protect OpenGL operations with global mutex based on runtime backend
    std::unique_lock<std::mutex> lock;
    if (backend_ == SiftBackend::GLSL) {
      lock = std::unique_lock<std::mutex>(
          *sift_opengl_mutexes_.at(sift_match_gpu_.gpu_index));
    }

    if (prev_image_id1_ == kInvalidImageId || prev_is_guided_ ||
        prev_image_id1_ != image1.image_id) {
      WarnIfMaxNumMatchesReachedGPU(image1.descriptors->data);
      sift_match_gpu_.SetDescriptors(
          0, image1.descriptors->data.rows(), image1.descriptors->data.data());
      prev_image_id1_ = image1.image_id;
    }

    if (prev_image_id2_ == kInvalidImageId || prev_is_guided_ ||
        prev_image_id2_ != image2.image_id) {
      WarnIfMaxNumMatchesReachedGPU(image2.descriptors->data);
      sift_match_gpu_.SetDescriptors(
          1, image2.descriptors->data.rows(), image2.descriptors->data.data());
      prev_image_id2_ = image2.image_id;
    }

    prev_is_guided_ = false;

    matches->resize(static_cast<size_t>(options_.max_num_matches));

    const int num_matches = sift_match_gpu_.GetSiftMatch(
        options_.max_num_matches,
        reinterpret_cast<uint32_t (*)[2]>(matches->data()),
        static_cast<float>(options_.sift->max_distance),
        static_cast<float>(options_.sift->max_ratio),
        options_.sift->cross_check);

    if (num_matches < 0) {
      LOG(ERROR) << "Feature matching failed. This is probably caused by "
                    "insufficient GPU memory. Consider reducing the maximum "
                    "number of features and/or matches.";
      matches->clear();
    } else {
      THROW_CHECK_LE(num_matches, matches->size());
      matches->resize(num_matches);
    }
  }

  void MatchGuided(const double max_error,
                   const Image& image1,