Improve docs; add consts

cpp/include/cudf/detail/tdigest/tdigest.hpp

@@ -145,7 +145,7 @@ std::unique_ptr<column> make_tdigest_column(size_type num_rows,
 /**
  * @brief Create an empty tdigest column.
  *
- * An empty tdigest column contains rows of length 0.
+ * An empty tdigest column contains specified number of rows of length 0.
  *
  * @param stream CUDA stream used for device memory operations and kernel launches.
  * @param mr Device memory resource used to allocate the returned column's device memory.

cpp/src/quantiles/tdigest/tdigest_aggregation.cu

@@ -366,8 +366,8 @@ std::unique_ptr<scalar> to_tdigest_scalar(std::unique_ptr<column>&& tdigest,
  * @param group_cluster_wl    Output.  The set of cluster weight limits for each group.
  * @param group_num_clusters  Output.  The number of output clusters for each input group.
  * @param group_cluster_offsets  Offsets per-group to the start of it's clusters
- * @param may_have_empty_clusters Whether or not there could be empty clusters. False if there
- * should be no empty clusters.
+ * @param may_have_empty_clusters Whether or not there could be empty clusters. It should be
+ * set to false only when there is no empty cluster.
  */
 
 template <typename GroupInfo, typename NearestWeightFunc, typename CumulativeWeight>
@@ -502,8 +502,8 @@ CUDF_KERNEL void generate_cluster_limits_kernel(int delta,
  * stream that falls before our current cluster limit
  * @param group_info         A functor which returns the info for the specified group (total weight,
  * size and start offset)
- * @param may_have_empty_clusters Whether or not there could be empty clusters. False if there
- * should be no empty clusters.
+ * @param may_have_empty_clusters Whether or not there could be empty clusters. It should be
+ * set to false only when there is no empty cluster.
  * @param stream CUDA stream used for device memory operations and kernel launches.
  * @param mr Device memory resource used to allocate the returned column's device memory
  *
@@ -720,8 +720,8 @@ struct compute_tdigests_keys_fn {
  * @param group_cluster_wl   Cluster weight limits for each group.
  * @param group_cluster_offsets R-value reference of offsets into the cluster weight limits.
  * @param total_clusters     Total number of clusters in all groups.
- * @param may_have_empty_clusters Whether or not there could be empty clusters. False if there
- * should be no empty clusters.
+ * @param may_have_empty_clusters Whether or not there could be empty clusters. It should be
+ * set to false only when there is no empty cluster.
  * @param stream CUDA stream used for device memory operations and kernel launches.
  * @param mr Device memory resource used to allocate the returned column's device memory
  *

cpp/tests/groupby/tdigest_tests.cu

@@ -514,7 +514,7 @@ std::unique_ptr<cudf::table> do_agg(
 {
   std::vector<cudf::column_view> keys;
   keys.push_back(key);
-  cudf::table_view key_table(keys);
+  cudf::table_view const key_table(keys);
 
   cudf::groupby::groupby gb(key_table);
   std::vector<cudf::groupby::aggregation_request> requests;
@@ -523,7 +523,7 @@ std::unique_ptr<cudf::table> do_agg(
   req.aggregations.push_back(make_agg());
   requests.push_back(std::move(req));
 
-  auto result = gb.aggregate(requests);
+  auto result = gb.aggregate(std::move(requests));
 
   std::vector<std::unique_ptr<cudf::column>> result_columns;
   for (auto&& c : result.first->release()) {
@@ -541,25 +541,26 @@ TEST_F(TDigestMergeTest, AllGroupsHaveEmptyClusters)
 {
   // The input must be sorted by the key.
   // See `aggregate_result_functor::operator()<aggregation::TDIGEST>` for details.
-  auto keys       = cudf::test::fixed_width_column_wrapper<int32_t>{{0, 0, 1, 1, 2}};
+  auto const keys      = cudf::test::fixed_width_column_wrapper<int32_t>{{0, 0, 1, 1, 2}};
+  auto const keys_view = cudf::column_view(keys);
   auto val_elems  = cudf::detail::make_counting_transform_iterator(0, [](auto i) { return i; });
   auto val_valids = cudf::detail::make_counting_transform_iterator(0, [](auto i) {
     // All values are null
     return false;
   });
-  auto vals       = cudf::test::fixed_width_column_wrapper<int32_t>{
-    val_elems, val_elems + cudf::column_view(keys).size(), val_valids};
+  auto const vals = cudf::test::fixed_width_column_wrapper<int32_t>{
+    val_elems, val_elems + keys_view.size(), val_valids};
 
   auto const delta = 10000;
 
   // Compute tdigest. The result should have 3 empty clusters, one per group.
-  auto compute_result = do_agg(cudf::column_view(keys), cudf::column_view(vals), [&delta]() {
+  auto const compute_result = do_agg(keys_view, cudf::column_view(vals), [&delta]() {
     return cudf::make_tdigest_aggregation<cudf::groupby_aggregation>(delta);
   });
 
-  auto expected_computed_keys = cudf::test::fixed_width_column_wrapper<int32_t>{{0, 1, 2}};
-  cudf::column_view expected_computed_keys_view{expected_computed_keys};
-  auto expected_computed_vals = cudf::tdigest::detail::make_tdigest_column_of_empty_clusters(
+  auto const expected_computed_keys = cudf::test::fixed_width_column_wrapper<int32_t>{{0, 1, 2}};
+  cudf::column_view const expected_computed_keys_view{expected_computed_keys};
+  auto const expected_computed_vals = cudf::tdigest::detail::make_tdigest_column_of_empty_clusters(
     expected_computed_keys_view.size(),
     cudf::get_default_stream(),
     rmm::mr::get_current_device_resource());
@@ -569,14 +570,14 @@ TEST_F(TDigestMergeTest, AllGroupsHaveEmptyClusters)
                                  compute_result->get_column(1).view());
 
   // Merge tdigest. The result should have 3 empty clusters, one per group.
-  auto merge_result =
+  auto const merge_result =
     do_agg(compute_result->get_column(0).view(), compute_result->get_column(1).view(), [&delta]() {
       return cudf::make_merge_tdigest_aggregation<cudf::groupby_aggregation>(delta);
     });
 
-  auto expected_merged_keys = cudf::test::fixed_width_column_wrapper<int32_t>{{0, 1, 2}};
-  cudf::column_view expected_merged_keys_view{expected_merged_keys};
-  auto expected_merged_vals = cudf::tdigest::detail::make_tdigest_column_of_empty_clusters(
+  auto const expected_merged_keys = cudf::test::fixed_width_column_wrapper<int32_t>{{0, 1, 2}};
+  cudf::column_view const expected_merged_keys_view{expected_merged_keys};
+  auto const expected_merged_vals = cudf::tdigest::detail::make_tdigest_column_of_empty_clusters(
     expected_merged_keys_view.size(),
     cudf::get_default_stream(),
     rmm::mr::get_current_device_resource());