Function AggregateReferenceColumn

tests/cpp/common/test_quantile.h:424–454

}

inline ReferenceColumn AggregateReferenceColumn(GeneratedColumn const& col) {
  std::vector<std::pair<float, double>> pairs;
  pairs.reserve(col.values.size());
  for (std::size_t i = 0; i < col.values.size(); ++i) {
    if (col.weights[i] == 0.0f) {
      continue;
    }
    pairs.emplace_back(col.values[i], static_cast<double>(col.weights[i]));
  }
  std::sort(pairs.begin(), pairs.end(),
            [](auto const& lhs, auto const& rhs) { return lhs.first < rhs.first; });

  std::vector<WeightedValue> out;
  for (auto const& [value, weight] : pairs) {
    if (!out.empty() && out.back().value == value) {
      out.back().weight += weight;
    } else {
      out.push_back({value, weight});
    }
  }

  ReferenceColumn ref;
  ref.values.reserve(out.size());
  ref.prefix_weights.reserve(out.size() + 1);
  ref.prefix_weights.push_back(0.0);
  for (auto const& v : out) {
    ref.values.push_back(v.value);
    ref.prefix_weights.push_back(ref.prefix_weights.back() + v.weight);
  }
  return ref;
}

inline double TotalWeight(ReferenceColumn const& col) { return col.prefix_weights.back(); }