Method Process

src/predictor/array_tree_layout.h:176–200

* @brief Traverse the top levels of the tree for the entire block_size. * * In the array layout, it is organized to guarantee that if a node at the current level * has index nidx, then the node index for the left child at the next level is always * 2*nidx, and the node index for the right child at the next level is always 2*nidx+1. * This greatly improves data locality. * * @p

   *               to the level next after kNumDeepLevels
   */
  void Process(common::Span<RegTree::FVec> fvec_tloc, std::size_t const block_size,
               bst_node_t* p_nidx) {
    for (int depth = 0; depth < kNumDeepLevels; ++depth) {
      std::size_t first_node = (1u << depth) - 1;

      for (std::size_t i = 0; i < block_size; ++i) {
        bst_node_t idx = p_nidx[i];

        const auto& feat = fvec_tloc[i];
        bst_feature_t split = split_index_[first_node + idx];
        auto fvalue = feat.GetFvalue(split);
        if constexpr (any_missing) {
          bool go_left = feat.IsMissing(split) ? default_left_[first_node + idx]
                                               : GetDecision(fvalue, first_node + idx);
          p_nidx[i] = 2 * idx + !go_left;
        } else {
          p_nidx[i] = 2 * idx + !GetDecision(fvalue, first_node + idx);
        }
      }
    }
    // Remap to the original index.
    for (std::size_t i = 0; i < block_size; ++i) {
      p_nidx[i] = nidx_in_tree_[p_nidx[i]];
    }
  }
};

template <bool has_categorical, bool any_missing, int num_deep_levels = 1, typename TreeView>