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Fix cudf::strings::is_fixed_point checking of overflow for decimal32 #9093

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Aug 25, 2021
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Fix cudf::strings::is_fixed_point checking of overflow for decimal32 #9093

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c349723
Fix is_fixed_point checking of overflow for decimal32
davidwendt Aug 23, 2021
1a35ab4
remove extra is from doxygen comment wording
davidwendt Aug 24, 2021
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26 changes: 17 additions & 9 deletions cpp/include/cudf/strings/detail/convert/fixed_point.cuh
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Original file line number Diff line number Diff line change
Expand Up @@ -17,6 +17,8 @@
#include <thrust/optional.h>
#include <thrust/pair.h>

#include <type_traits>

namespace cudf {
namespace strings {
namespace detail {
Expand All @@ -27,17 +29,22 @@ namespace detail {
* This is reads everything up to the exponent 'e' notation.
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* The return includes the integer digits and any exponent offset.
*
* @tparam UnsignedDecimalType The unsigned version of the desired decimal type.
* Use the `std::make_unsigned_t` to create the
* unsigned type from the storage type.
*
* @param[in,out] iter Start of characters to parse
* @param[in] end End of characters to parse
* @return Integer component and exponent offset.
*/
__device__ inline thrust::pair<uint64_t, int32_t> parse_integer(char const*& iter,
char const* iter_end,
const char decimal_pt_char = '.')
template <typename UnsignedDecimalType>
__device__ inline thrust::pair<UnsignedDecimalType, int32_t> parse_integer(
char const*& iter, char const* iter_end, const char decimal_pt_char = '.')
{
// highest value where another decimal digit cannot be appended without an overflow;
// this preserves the most digits when scaling the final result
constexpr uint64_t decimal_max = (std::numeric_limits<uint64_t>::max() - 9L) / 10L;
// this preserves the most digits when scaling the final result for this type
constexpr UnsignedDecimalType decimal_max =
(std::numeric_limits<UnsignedDecimalType>::max() - 9L) / 10L;

uint64_t value = 0; // for checking overflow
int32_t exp_offset = 0;
Expand All @@ -56,7 +63,7 @@ __device__ inline thrust::pair<uint64_t, int32_t> parse_integer(char const*& ite
if (value > decimal_max) {
exp_offset += static_cast<int32_t>(!decimal_found);
} else {
value = (value * 10) + static_cast<uint64_t>(ch - '0');
value = (value * 10) + static_cast<UnsignedDecimalType>(ch - '0');
exp_offset -= static_cast<int32_t>(decimal_found);
}
}
Expand Down Expand Up @@ -130,7 +137,8 @@ __device__ DecimalType parse_decimal(char const* iter, char const* iter_end, int
// if string begins with a sign, continue with next character
if (sign != 0) ++iter;

auto [value, exp_offset] = parse_integer(iter, iter_end);
using UnsignedDecimalType = std::make_unsigned_t<DecimalType>;
auto [value, exp_offset] = parse_integer<UnsignedDecimalType>(iter, iter_end);
if (value == 0) { return DecimalType{0}; }

// check for exponent
Expand All @@ -143,9 +151,9 @@ __device__ DecimalType parse_decimal(char const* iter, char const* iter_end, int

// shift the output value based on the exp_ten and the scale values
if (exp_ten < scale) {
value = value / static_cast<uint64_t>(exp10(static_cast<double>(scale - exp_ten)));
value = value / static_cast<UnsignedDecimalType>(exp10(static_cast<double>(scale - exp_ten)));
} else {
value = value * static_cast<uint64_t>(exp10(static_cast<double>(exp_ten - scale)));
value = value * static_cast<UnsignedDecimalType>(exp10(static_cast<double>(exp_ten - scale)));
}

return static_cast<DecimalType>(value) * (sign == 0 ? 1 : sign);
Expand Down
12 changes: 6 additions & 6 deletions cpp/src/strings/convert/convert_fixed_point.cu
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Expand Up @@ -97,7 +97,8 @@ struct string_to_decimal_check_fn {

auto const iter_end = d_str.data() + d_str.size_bytes();

auto [value, exp_offset] = parse_integer(iter, iter_end);
using UnsignedDecimalType = std::make_unsigned_t<DecimalType>;
auto [value, exp_offset] = parse_integer<UnsignedDecimalType>(iter, iter_end);

// only exponent notation is expected here
if ((iter < iter_end) && (*iter != 'e' && *iter != 'E')) { return false; }
Expand All @@ -112,11 +113,10 @@ struct string_to_decimal_check_fn {
exp_ten += exp_offset;

// finally, check for overflow based on the exp_ten and scale values
return (exp_ten < scale)
? true
: value <= static_cast<uint64_t>(
std::numeric_limits<DecimalType>::max() /
static_cast<DecimalType>(exp10(static_cast<double>(exp_ten - scale))));
return (exp_ten < scale) or
value <= static_cast<UnsignedDecimalType>(
std::numeric_limits<DecimalType>::max() /
static_cast<DecimalType>(exp10(static_cast<double>(exp_ten - scale))));
}
};

Expand Down
28 changes: 18 additions & 10 deletions cpp/tests/strings/fixed_point_tests.cpp
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Expand Up @@ -189,31 +189,39 @@ TEST_F(StringsConvertTest, IsFixedPoint)
"9223372036854775807",
"-9223372036854775807",
"9223372036854775808",
"9223372036854775808000",
"100E2147483648",
});
results = cudf::strings::is_fixed_point(cudf::strings_column_view(big_numbers),
results = cudf::strings::is_fixed_point(cudf::strings_column_view(big_numbers),
cudf::data_type{cudf::type_id::DECIMAL32});
auto const expected32 =
cudf::test::fixed_width_column_wrapper<bool>({true, true, false, false, false, false, false});
auto const expected32 = cudf::test::fixed_width_column_wrapper<bool>(
{true, true, false, false, false, false, false, false});
CUDF_TEST_EXPECT_COLUMNS_EQUIVALENT(*results, expected32);

results = cudf::strings::is_fixed_point(cudf::strings_column_view(big_numbers),
results = cudf::strings::is_fixed_point(cudf::strings_column_view(big_numbers),
cudf::data_type{cudf::type_id::DECIMAL64});
auto const expected64 =
cudf::test::fixed_width_column_wrapper<bool>({true, true, true, true, true, false, false});
auto const expected64 = cudf::test::fixed_width_column_wrapper<bool>(
{true, true, true, true, true, false, false, false});
CUDF_TEST_EXPECT_COLUMNS_EQUIVALENT(*results, expected64);

results = cudf::strings::is_fixed_point(
cudf::strings_column_view(big_numbers),
cudf::data_type{cudf::type_id::DECIMAL32, numeric::scale_type{10}});
auto const expected32_scaled =
cudf::test::fixed_width_column_wrapper<bool>({true, true, true, true, true, true, false});
auto const expected32_scaled = cudf::test::fixed_width_column_wrapper<bool>(
{true, true, true, true, true, true, false, false});
CUDF_TEST_EXPECT_COLUMNS_EQUIVALENT(*results, expected32_scaled);

results = cudf::strings::is_fixed_point(
cudf::strings_column_view(big_numbers),
cudf::data_type{cudf::type_id::DECIMAL64, numeric::scale_type{10}});
auto const expected64_scaled_positive =
cudf::test::fixed_width_column_wrapper<bool>({true, true, true, true, true, true, true, false});
CUDF_TEST_EXPECT_COLUMNS_EQUIVALENT(*results, expected64_scaled_positive);

results = cudf::strings::is_fixed_point(
cudf::strings_column_view(big_numbers),
cudf::data_type{cudf::type_id::DECIMAL64, numeric::scale_type{-5}});
auto const expected64_scaled =
cudf::test::fixed_width_column_wrapper<bool>({true, true, true, false, false, false, false});
auto const expected64_scaled = cudf::test::fixed_width_column_wrapper<bool>(
{true, true, true, false, false, false, false, false});
CUDF_TEST_EXPECT_COLUMNS_EQUIVALENT(*results, expected64_scaled);
}