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Fix edge case in tdigest scalar generation for groups containing all nulls. #9551

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merged 5 commits into from
Nov 3, 2021
Merged

Fix edge case in tdigest scalar generation for groups containing all nulls. #9551

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98508dd
Handle edge case where an empty group of inputs is composed entirely …
nvdbaranec Oct 27, 2021
1dd8512
Tweak a merge test by adding some additional nulls.
nvdbaranec Oct 28, 2021
d0be464
Merge branch 'branch-21.12' into tdigest_null_groups_fix
nvdbaranec Nov 2, 2021
8cee72c
Merge branch 'branch-21.12' into tdigest_null_groups_fix
nvdbaranec Nov 2, 2021
c2efde7
PR review changes.
nvdbaranec Nov 3, 2021
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52 changes: 25 additions & 27 deletions cpp/src/groupby/sort/group_tdigest.cu
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Original file line number Diff line number Diff line change
Expand Up @@ -57,8 +57,10 @@ struct make_centroid {

centroid operator() __device__(size_type index)
{
return {
static_cast<double>(col.element<T>(index)), col.is_valid(index) ? 1 : 0, col.is_valid(index)};
auto const is_valid = col.is_valid(index);
auto const mean = is_valid ? static_cast<double>(col.element<T>(index)) : 0.0;
auto const weight = is_valid ? 1.0 : 0.0;
return {mean, weight, is_valid};
}
};

Expand Down Expand Up @@ -396,7 +398,7 @@ generate_group_cluster_info(int delta,
has_nulls);

// generate group cluster offsets (where the clusters for a given group start and end)
auto group_cluster_offsets = cudf::make_fixed_width_column(
auto group_cluster_offsets = cudf::make_numeric_column(
data_type{type_id::INT32}, num_groups + 1, mask_state::UNALLOCATED, stream, mr);
auto cluster_size = cudf::detail::make_counting_transform_iterator(
0, [group_num_clusters = group_num_clusters.begin(), num_groups] __device__(size_type index) {
Expand Down Expand Up @@ -467,24 +469,20 @@ std::unique_ptr<column> build_output_column(size_type num_rows,
}

// otherwise we need to strip out the stubs.

auto remove_stubs = [&](column_view const& col, size_type num_stubs) {
auto result = cudf::make_numeric_column(
data_type{type_id::FLOAT64}, col.size() - num_stubs, mask_state::UNALLOCATED, stream, mr);
thrust::remove_copy_if(rmm::exec_policy(stream),
col.begin<double>(),
col.end<double>(),
thrust::make_counting_iterator(0),
result->mutable_view().begin<double>(),
is_stub_weight);
return result;
};
// remove from the means and weights column
auto _means = cudf::make_fixed_width_column(
data_type{type_id::FLOAT64}, means->size() - num_stubs, mask_state::UNALLOCATED, stream, mr);
thrust::remove_copy_if(rmm::exec_policy(stream),
means->view().begin<double>(),
means->view().end<double>(),
thrust::make_counting_iterator(0),
_means->mutable_view().begin<double>(),
is_stub_weight);
auto _weights = cudf::make_fixed_width_column(
data_type{type_id::FLOAT64}, weights->size() - num_stubs, mask_state::UNALLOCATED, stream, mr);
thrust::remove_copy_if(rmm::exec_policy(stream),
weights->view().begin<double>(),
weights->view().end<double>(),
thrust::make_counting_iterator(0),
_weights->mutable_view().begin<double>(),
is_stub_weight);
auto _means = remove_stubs(*means, num_stubs);
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auto _weights = remove_stubs(*weights, num_stubs);

// adjust offsets.
rmm::device_uvector<offset_type> sizes(num_rows, stream);
Expand Down Expand Up @@ -609,9 +607,9 @@ std::unique_ptr<column> compute_tdigests(int delta,
});

// mean and weight data
auto centroid_means = cudf::make_fixed_width_column(
auto centroid_means = cudf::make_numeric_column(
data_type{type_id::FLOAT64}, total_clusters, mask_state::UNALLOCATED, stream, mr);
auto centroid_weights = cudf::make_fixed_width_column(
auto centroid_weights = cudf::make_numeric_column(
data_type{type_id::FLOAT64}, total_clusters, mask_state::UNALLOCATED, stream, mr);
// reduce the centroids down by key.
cudf::mutable_column_view mean_col(*centroid_means);
Expand Down Expand Up @@ -697,9 +695,9 @@ struct typed_group_tdigest {
auto d_col = cudf::column_device_view::create(col);

// compute min and max columns
auto min_col = cudf::make_fixed_width_column(
auto min_col = cudf::make_numeric_column(
data_type{type_id::FLOAT64}, num_groups, mask_state::UNALLOCATED, stream, mr);
auto max_col = cudf::make_fixed_width_column(
auto max_col = cudf::make_numeric_column(
data_type{type_id::FLOAT64}, num_groups, mask_state::UNALLOCATED, stream, mr);
thrust::transform(
rmm::exec_policy(stream),
Expand Down Expand Up @@ -841,7 +839,7 @@ std::unique_ptr<column> group_merge_tdigest(column_view const& input,
});

// generate min and max values
auto merged_min_col = cudf::make_fixed_width_column(
auto merged_min_col = cudf::make_numeric_column(
data_type{type_id::FLOAT64}, num_groups, mask_state::UNALLOCATED, stream, mr);
auto min_iter = thrust::make_transform_iterator(
thrust::make_zip_iterator(thrust::make_tuple(tdv.min_begin(), tdv.size_begin())),
Expand All @@ -855,7 +853,7 @@ std::unique_ptr<column> group_merge_tdigest(column_view const& input,
thrust::equal_to<size_type>{}, // key equality check
thrust::minimum<double>{});

auto merged_max_col = cudf::make_fixed_width_column(
auto merged_max_col = cudf::make_numeric_column(
data_type{type_id::FLOAT64}, num_groups, mask_state::UNALLOCATED, stream, mr);
auto max_iter = thrust::make_transform_iterator(
thrust::make_zip_iterator(thrust::make_tuple(tdv.max_begin(), tdv.size_begin())),
Expand Down Expand Up @@ -905,7 +903,7 @@ std::unique_ptr<column> group_merge_tdigest(column_view const& input,

// generate cumulative weights
auto merged_weights = merged->get_column(1).view();
auto cumulative_weights = cudf::make_fixed_width_column(
auto cumulative_weights = cudf::make_numeric_column(
data_type{type_id::FLOAT64}, merged_weights.size(), mask_state::UNALLOCATED);
auto keys = cudf::detail::make_counting_transform_iterator(
0,
Expand Down