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Handle nullptr return value from bitmask_or in distinct_count #13590

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Jun 21, 2023
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Handle nullptr return value from bitmask_or in distinct_count #13590

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af57c7d
Handle nullptr return value from bitmask_or in distinct_count
wence- Jun 20, 2023
ae8bd56
Clarify comment
wence- Jun 20, 2023
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17 changes: 13 additions & 4 deletions cpp/src/stream_compaction/distinct_count.cu
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Original file line number Diff line number Diff line change
Expand Up @@ -150,15 +150,24 @@ cudf::size_type distinct_count(table_view const& keys,
stream.value()};

auto const iter = thrust::counting_iterator<cudf::size_type>(0);
// when nulls are equal, insert non-null rows only to improve efficiency
// when nulls are equal, we skip hashing any row that has a null
// in every column to improve efficiency.
if (nulls_equal == null_equality::EQUAL and has_nulls) {
thrust::counting_iterator<size_type> stencil(0);
// We must consider a row if any of its column entries is valid,
// hence OR together the validities of the columns.
auto const [row_bitmask, null_count] =
cudf::detail::bitmask_or(keys, stream, rmm::mr::get_current_device_resource());
row_validity pred{static_cast<bitmask_type const*>(row_bitmask.data())};

return key_set.insert_if(iter, iter + num_rows, stencil, pred, stream.value()) +
static_cast<cudf::size_type>(null_count > 0);
// Unless all columns have a null mask, row_bitmask will be
// null, and null_count will be zero. Equally, unless there is
// some row which is null in all columns, null_count will be
// zero. So, it is only when null_count is not zero that we need
// to do a filtered insertion.
if (null_count > 0) {
row_validity pred{static_cast<bitmask_type const*>(row_bitmask.data())};
return key_set.insert_if(iter, iter + num_rows, stencil, pred, stream.value()) + 1;
}
}
// otherwise, insert all
return key_set.insert(iter, iter + num_rows, stream.value());
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10 changes: 10 additions & 0 deletions cpp/tests/stream_compaction/distinct_count_tests.cpp
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Expand Up @@ -274,6 +274,16 @@ TEST_F(DistinctCount, TableWithNull)
EXPECT_EQ(10, cudf::distinct_count(input, null_equality::UNEQUAL));
}

TEST_F(DistinctCount, TableWithSomeNull)
{
cudf::test::fixed_width_column_wrapper<int32_t> col1{{1, 2, 3, 4, 5, 6}, {1, 0, 1, 0, 1, 0}};
cudf::test::fixed_width_column_wrapper<int32_t> col2{{1, 1, 1, 1, 1, 1}};
cudf::table_view input{{col1, col2}};

EXPECT_EQ(4, cudf::distinct_count(input, null_equality::EQUAL));
EXPECT_EQ(6, cudf::distinct_count(input, null_equality::UNEQUAL));
}

TEST_F(DistinctCount, EmptyColumnedTable)
{
std::vector<cudf::column_view> cols{};
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