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Fix rint for near-halfway cases #137

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Merged
merged 1 commit into from
Aug 29, 2025
Merged

Fix rint for near-halfway cases #137

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11 changes: 10 additions & 1 deletion quaddtype/numpy_quaddtype/src/ops.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -40,7 +40,16 @@ quad_absolute(const Sleef_quad *op)
static inline Sleef_quad
quad_rint(const Sleef_quad *op)
{
return Sleef_rintq1(*op);
Sleef_quad halfway = Sleef_addq1_u05(
Sleef_truncq1(*op),
Sleef_copysignq1(Sleef_cast_from_doubleq1(0.5), *op)
);

// Sleef_rintq1 does not handle some near-halfway cases correctly, so we
// manually round up or down when x is not exactly halfway
return Sleef_icmpeqq1(*op, halfway) ? Sleef_rintq1(*op) : (
Sleef_icmpleq1(*op, halfway) ? Sleef_floorq1(*op) : Sleef_ceilq1(*op)
);
}

static inline Sleef_quad
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6 changes: 6 additions & 0 deletions quaddtype/tests/test_quaddtype.py
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Expand Up @@ -209,6 +209,12 @@ def test_rounding_functions(op, val):
quad_result), f"Zero sign mismatch for {op}({val})"


def test_rint_near_halfway():
assert np.rint(QuadPrecision("7.4999999999999999")) == 7
assert np.rint(QuadPrecision("7.49999999999999999")) == 7
assert np.rint(QuadPrecision("7.5")) == 8


@pytest.mark.parametrize("op", ["exp", "exp2"])
@pytest.mark.parametrize("val", [
# Basic cases
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