Method MergeInput

cpp/src/arrow/util/tdigest.cc:244–272

merge input data with current tdigest

  // merge input data with current tdigest
  void MergeInput(std::vector<double>& input) {
    total_weight_ += input.size();

    std::sort(input.begin(), input.end());
    min_ = std::min(min_, input.front());
    max_ = std::max(max_, input.back());

    // pick next minimal centroid from input and tdigest, feed to merger
    merger_.Reset(total_weight_, &tdigests_[1 - current_]);
    const auto& td = tdigests_[current_];
    uint32_t tdigest_index = 0, input_index = 0;
    while (tdigest_index < td.size() && input_index < input.size()) {
      if (td[tdigest_index].mean < input[input_index]) {
        merger_.Add(td[tdigest_index++]);
      } else {
        merger_.Add(Centroid{input[input_index++], 1});
      }
    }
    while (tdigest_index < td.size()) {
      merger_.Add(td[tdigest_index++]);
    }
    while (input_index < input.size()) {
      merger_.Add(Centroid{input[input_index++], 1});
    }
    merger_.Reset(0, nullptr);

    input.resize(0);
    current_ = 1 - current_;
  }

  double Quantile(double q) const {
    const auto& td = tdigests_[current_];