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DX-90291: Gandiva: fix round(double, scale) overflow for large values #148

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Merged
victor6567758 merged 2 commits into from
Oct 17, 2026
Merged

DX-90291: Gandiva: fix round(double, scale) overflow for large values #148

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4cbf105
DX-90291: Gandiva: fix round(double, scale) overflow for large values
victor6567758 Oct 15, 2026
59b548e
DX-90291: Rename round limit constant, document float32 use
victor6567758 Oct 16, 2026
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21 changes: 14 additions & 7 deletions cpp/src/gandiva/precompiled/extended_math_ops.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -304,14 +304,21 @@ gdv_float64 bround_float64(gdv_float64 num) {
return num - diff_num;
}

// limit for abs(number * 10^scale_multiplier), computed in double - works for float32 and float64 versions.
// at or above 2^52 double (scaled) has no fractional part, so there is nothing to round
static const gdv_float64 kMaxRoundableScaledValue = static_cast<gdv_float64>(1LL << 52);
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// rounds the number to the given scale
#define ROUND_DECIMAL_TO_SCALE(TYPE) \
FORCE_INLINE \
gdv_##TYPE round_##TYPE##_int32(gdv_##TYPE number, gdv_int32 out_scale) { \
gdv_float64 scale_multiplier = get_scale_multiplier(out_scale); \
return static_cast<gdv_##TYPE>( \
trunc(number * scale_multiplier + ((number >= 0) ? 0.5 : -0.5)) / \
scale_multiplier); \
// every ordered comparison with NaN is false: <, <=, >, >= and ==
#define ROUND_DECIMAL_TO_SCALE(TYPE) \
FORCE_INLINE \
gdv_##TYPE round_##TYPE##_int32(gdv_##TYPE number, gdv_int32 out_scale) { \
gdv_float64 scale_multiplier = get_scale_multiplier(out_scale); \
if (!(fabs(number) < kMaxRoundableScaledValue / scale_multiplier)) { \
return number; \
} \
gdv_float64 scaled = number * scale_multiplier; \
return static_cast<gdv_##TYPE>(trunc(scaled + ((number >= 0) ? 0.5 : -0.5)) / \
scale_multiplier); \
}

ROUND_DECIMAL_TO_SCALE(float32)
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37 changes: 37 additions & 0 deletions cpp/src/gandiva/precompiled/extended_math_ops_test.cc
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Expand Up @@ -153,6 +153,20 @@ TEST(TestExtendedMathOps, TestRoundDecimal) {
EXPECT_FLOAT_EQ(round_float32_int32(static_cast<float>(9.134123), 2), 9.13f);
EXPECT_FLOAT_EQ(round_float32_int32(static_cast<float>(-1.923), 1), -1.9f);

const float max_float = std::numeric_limits<float>::max();
const float lowest_float = std::numeric_limits<float>::lowest();
EXPECT_EQ(round_float32_int32(max_float, 100), max_float);
EXPECT_EQ(round_float32_int32(lowest_float, 100), lowest_float);
EXPECT_EQ(round_float32_int32(1.0e30f, 2), 1.0e30f);
EXPECT_EQ(round_float32_int32(451.65f, 100), 451.65f);
EXPECT_EQ(round_float32_int32(-451.65f, 100), -451.65f);
EXPECT_EQ(round_float32_int32(16777216.0f, 2), 16777216.0f);

const float limit_float = static_cast<float>(std::ldexp(1.0, 52) / 100.0);
const float just_above_float = std::nextafter(limit_float, max_float);
EXPECT_EQ(round_float32_int32(limit_float, 2), limit_float);
EXPECT_EQ(round_float32_int32(just_above_float, 2), just_above_float);

VerifyFuzzyEquals(round_float64(1234.245), 1234);
VerifyFuzzyEquals(round_float64(-11.7892), -12);
VerifyFuzzyEquals(round_float64(1.4999999), 1);
Expand All @@ -165,6 +179,29 @@ TEST(TestExtendedMathOps, TestRoundDecimal) {
EXPECT_EQ(std::signbit(round_float64_int32(0, -2)), 0);
VerifyFuzzyEquals(round_float64_int32((double)INT_MAX + 1, 0), (double)INT_MAX + 1);
VerifyFuzzyEquals(round_float64_int32((double)INT_MIN - 1, 0), (double)INT_MIN - 1);

const double max_double = std::numeric_limits<double>::max();
const double lowest_double = std::numeric_limits<double>::lowest();
EXPECT_EQ(round_float64_int32(2.29e208, 100), 2.29e208);
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EXPECT_EQ(round_float64_int32(-2.29e208, 100), -2.29e208);
EXPECT_EQ(round_float64_int32(max_double, 100), max_double);
EXPECT_EQ(round_float64_int32(lowest_double, 100), lowest_double);
EXPECT_EQ(round_float64_int32(451.65, 100), 451.65);
EXPECT_EQ(round_float64_int32(-451.65, 100), -451.65);

const double ticket_val = 2.2926114935177252E208;
EXPECT_EQ(round_float64_int32(ticket_val, 100), ticket_val);
EXPECT_EQ(round_float64_int32(-ticket_val, 100), -ticket_val);
for (gdv_int32 scale : {3, 4, 7, 8, 10, -100}) {
EXPECT_EQ(round_float64_int32(ticket_val, scale), ticket_val);
EXPECT_EQ(round_float64_int32(-ticket_val, scale), -ticket_val);
}
EXPECT_EQ(round_float64_int32(1.5, -100), 0);

const double limit_double = std::ldexp(1.0, 52) / 100.0;
const double just_above_double = std::nextafter(limit_double, max_double);
EXPECT_EQ(round_float64_int32(limit_double, 2), limit_double);
EXPECT_EQ(round_float64_int32(just_above_double, 2), just_above_double);
}

TEST(TestExtendedMathOps, TestBRoundDecimal) {
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