Centralization of tdigest aggregation code.

cpp/CMakeLists.txt

@@ -265,7 +265,6 @@ add_library(
   src/groupby/sort/group_rank_scan.cu
   src/groupby/sort/group_replace_nulls.cu
   src/groupby/sort/group_sum_scan.cu
-  src/groupby/sort/group_tdigest.cu
   src/groupby/sort/sort_helper.cu
   src/hash/hashing.cu
   src/hash/md5_hash.cu
@@ -357,7 +356,8 @@ add_library(
   src/partitioning/partitioning.cu
   src/partitioning/round_robin.cu
   src/quantiles/tdigest/tdigest.cu
-  src/quantiles/tdigest/tdigest_column_view.cpp
+  src/quantiles/tdigest/tdigest_aggregation.cu
+  src/quantiles/tdigest/tdigest_column_view.cpp  
   src/quantiles/quantile.cu
   src/quantiles/quantiles.cu
   src/reductions/all.cu

cpp/src/groupby/sort/aggregate.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2019-2021, NVIDIA CORPORATION.
+ * Copyright (c) 2019-2022, NVIDIA CORPORATION.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -35,6 +35,8 @@
 #include <cudf/table/table_view.hpp>
 #include <cudf/types.hpp>
 
+#include <quantiles/tdigest/tdigest.hpp>
+
 #include <rmm/cuda_stream_view.hpp>
 
 #include <memory>
@@ -700,7 +702,7 @@ void aggregate_result_functor::operator()<aggregation::TDIGEST>(aggregation cons
 
   cache.add_result(values,
                    agg,
-                   detail::group_tdigest(
+                   cudf::detail::tdigest::group_tdigest(
                      get_sorted_values(),
                      helper.group_offsets(stream),
                      helper.group_labels(stream),
@@ -744,13 +746,13 @@ void aggregate_result_functor::operator()<aggregation::MERGE_TDIGEST>(aggregatio
     dynamic_cast<cudf::detail::merge_tdigest_aggregation const&>(agg).max_centroids;
   cache.add_result(values,
                    agg,
-                   detail::group_merge_tdigest(get_grouped_values(),
-                                               helper.group_offsets(stream),
-                                               helper.group_labels(stream),
-                                               helper.num_groups(stream),
-                                               max_centroids,
-                                               stream,
-                                               mr));
+                   cudf::detail::tdigest::group_merge_tdigest(get_grouped_values(),
+                                                              helper.group_offsets(stream),
+                                                              helper.group_labels(stream),
+                                                              helper.num_groups(stream),
+                                                              max_centroids,
+                                                              stream,
+                                                              mr));
 };
 
 }  // namespace detail

cpp/src/groupby/sort/group_reductions.hpp

@@ -483,94 +483,6 @@ std::unique_ptr<column> group_correlation(column_view const& covariance,
                                           rmm::cuda_stream_view stream,
                                           rmm::mr::device_memory_resource* mr);
 
-/**
- * @brief Generate a tdigest column from a grouped set of numeric input values.
- *
- * The tdigest column produced is of the following structure:
- *
- * struct {
- *   // centroids for the digest
- *   list {
- *    struct {
- *      double    // mean
- *      double    // weight
- *    },
- *    ...
- *   }
- *   // these are from the input stream, not the centroids. they are used
- *   // during the percentile_approx computation near the beginning or
- *   // end of the quantiles
- *   double       // min
- *   double       // max
- * }
- *
- * Each output row is a single tdigest.  The length of the row is the "size" of the
- * tdigest, each element of which represents a weighted centroid (mean, weight).
- *
- * @param values Grouped (and sorted) values to merge.
- * @param group_offsets Offsets of groups' starting points within @p values.
- * @param group_labels 0-based ID of group that the corresponding value belongs to
- * @param group_valid_counts Per-group counts of valid elements.
- * @param num_groups Number of groups.
- * @param max_centroids Parameter controlling the level of compression of the tdigest. Higher
- * values result in a larger, more precise tdigest.
- * @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
- *
- * @returns tdigest column, with 1 tdigest per row
- */
-std::unique_ptr<column> group_tdigest(column_view const& values,
-                                      cudf::device_span<size_type const> group_offsets,
-                                      cudf::device_span<size_type const> group_labels,
-                                      cudf::device_span<size_type const> group_valid_counts,
-                                      size_type num_groups,
-                                      int max_centroids,
-                                      rmm::cuda_stream_view stream,
-                                      rmm::mr::device_memory_resource* mr);
-
-/**
- * @brief Merges tdigests within the same group to generate a new tdigest.
- *
- * The tdigest column produced is of the following structure:
- *
- * struct {
- *   // centroids for the digest
- *   list {
- *    struct {
- *      double    // mean
- *      double    // weight
- *    },
- *    ...
- *   }
- *   // these are from the input stream, not the centroids. they are used
- *   // during the percentile_approx computation near the beginning or
- *   // end of the quantiles
- *   double       // min
- *   double       // max
- * }
- *
- * Each output row is a single tdigest.  The length of the row is the "size" of the
- * tdigest, each element of which represents a weighted centroid (mean, weight).
- *
- * @param values Grouped tdigests to merge.
- * @param group_offsets Offsets of groups' starting points within @p values.
- * @param group_labels 0-based ID of group that the corresponding value belongs to
- * @param num_groups Number of groups.
- * @param max_centroids Parameter controlling the level of compression of the tdigest. Higher
- * values result in a larger, more precise tdigest.
- * @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
- *
- * @returns tdigest column, with 1 tdigest per row
- */
-std::unique_ptr<column> group_merge_tdigest(column_view const& values,
-                                            cudf::device_span<size_type const> group_offsets,
-                                            cudf::device_span<size_type const> group_labels,
-                                            size_type num_groups,
-                                            int max_centroids,
-                                            rmm::cuda_stream_view stream,
-                                            rmm::mr::device_memory_resource* mr);
-
 }  // namespace detail
 }  // namespace groupby
 }  // namespace cudf

cpp/src/quantiles/tdigest/tdigest.hpp

@@ -0,0 +1,113 @@
+/*
+ * Copyright (c) 2022, NVIDIA CORPORATION.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+
+namespace cudf {
+namespace detail {
+namespace tdigest {
+
+/**
+ * @brief Generate a tdigest column from a grouped set of numeric input values.
+ *
+ * The tdigest column produced is of the following structure:
+ *
+ * struct {
+ *   // centroids for the digest
+ *   list {
+ *    struct {
+ *      double    // mean
+ *      double    // weight
+ *    },
+ *    ...
+ *   }
+ *   // these are from the input stream, not the centroids. they are used
+ *   // during the percentile_approx computation near the beginning or
+ *   // end of the quantiles
+ *   double       // min
+ *   double       // max
+ * }
+ *
+ * Each output row is a single tdigest.  The length of the row is the "size" of the
+ * tdigest, each element of which represents a weighted centroid (mean, weight).
+ *
+ * @param values Grouped (and sorted) values to merge.
+ * @param group_offsets Offsets of groups' starting points within @p values.
+ * @param group_labels 0-based ID of group that the corresponding value belongs to
+ * @param group_valid_counts Per-group counts of valid elements.
+ * @param num_groups Number of groups.
+ * @param max_centroids Parameter controlling the level of compression of the tdigest. Higher
+ * values result in a larger, more precise tdigest.
+ * @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
+ *
+ * @returns tdigest column, with 1 tdigest per row
+ */
+std::unique_ptr<column> group_tdigest(column_view const& values,
+                                      cudf::device_span<size_type const> group_offsets,
+                                      cudf::device_span<size_type const> group_labels,
+                                      cudf::device_span<size_type const> group_valid_counts,
+                                      size_type num_groups,
+                                      int max_centroids,
+                                      rmm::cuda_stream_view stream,
+                                      rmm::mr::device_memory_resource* mr);
+
+/**
+ * @brief Merges tdigests within the same group to generate a new tdigest.
+ *
+ * The tdigest column produced is of the following structure:
+ *
+ * struct {
+ *   // centroids for the digest
+ *   list {
+ *    struct {
+ *      double    // mean
+ *      double    // weight
+ *    },
+ *    ...
+ *   }
+ *   // these are from the input stream, not the centroids. they are used
+ *   // during the percentile_approx computation near the beginning or
+ *   // end of the quantiles
+ *   double       // min
+ *   double       // max
+ * }
+ *
+ * Each output row is a single tdigest.  The length of the row is the "size" of the
+ * tdigest, each element of which represents a weighted centroid (mean, weight).
+ *
+ * @param values Grouped tdigests to merge.
+ * @param group_offsets Offsets of groups' starting points within @p values.
+ * @param group_labels 0-based ID of group that the corresponding value belongs to
+ * @param num_groups Number of groups.
+ * @param max_centroids Parameter controlling the level of compression of the tdigest. Higher
+ * values result in a larger, more precise tdigest.
+ * @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
+ *
+ * @returns tdigest column, with 1 tdigest per row
+ */
+std::unique_ptr<column> group_merge_tdigest(column_view const& values,
+                                            cudf::device_span<size_type const> group_offsets,
+                                            cudf::device_span<size_type const> group_labels,
+                                            size_type num_groups,
+                                            int max_centroids,
+                                            rmm::cuda_stream_view stream,
+                                            rmm::mr::device_memory_resource* mr);
+
+}  // namespace tdigest
+}  // namespace detail
+}  // namespace cudf

cpp/src/groupby/sort/group_tdigest.cu → cpp/src/quantiles/tdigest/tdigest_aggregation.cu

@@ -37,8 +37,8 @@
 #include <thrust/iterator/discard_iterator.h>
 
 namespace cudf {
-namespace groupby {
 namespace detail {
+namespace tdigest {
 
 using namespace cudf::tdigest;
 
@@ -1008,6 +1008,6 @@ std::unique_ptr<column> group_merge_tdigest(column_view const& input,
                           mr);
 }
 
+}  // namespace tdigest
 }  // namespace detail
-}  // namespace groupby
 }  // namespace cudf