Method CalMapAtK

src/metric/map_metric.hpp:80–110

  }

  void CalMapAtK(std::vector<int> ks, data_size_t npos, const label_t* label,
                 const double* score, data_size_t num_data, std::vector<double>* out) const {
    // get sorted indices by score
    std::vector<data_size_t> sorted_idx;
    for (data_size_t i = 0; i < num_data; ++i) {
      sorted_idx.emplace_back(i);
    }
    std::stable_sort(sorted_idx.begin(), sorted_idx.end(),
                     [score](data_size_t a, data_size_t b) {return score[a] > score[b]; });

    int num_hit = 0;
    double sum_ap = 0.0f;
    data_size_t cur_left = 0;
    for (size_t i = 0; i < ks.size(); ++i) {
      data_size_t cur_k = static_cast<data_size_t>(ks[i]);
      if (cur_k > num_data) { cur_k = num_data; }
      for (data_size_t j = cur_left; j < cur_k; ++j) {
        data_size_t idx = sorted_idx[j];
        if (label[idx] > 0.5f) {
          ++num_hit;
          sum_ap += static_cast<double>(num_hit) / (j + 1.0f);
        }
      }
      if (npos > 0) {
        (*out)[i] = sum_ap / std::min(npos, cur_k);
      } else {
        (*out)[i] = 1.0f;
      }
      cur_left = cur_k;
    }
  }
  std::vector<double> Eval(const double* score, const ObjectiveFunction*) const override {
    // some buffers for multi-threading sum up
    std::vector<std::vector<double>> result_buffer_;