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Fix: Making pow compatible with cpython pow signature #251

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Merged
ngoldbaum merged 1 commit into from
Jan 9, 2026
+23 −2
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Fix: Making pow compatible with cpython pow signature #251

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14 changes: 13 additions & 1 deletion quaddtype/numpy_quaddtype/src/scalar_ops.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -228,11 +228,23 @@ QuadPrecision_int(QuadPrecisionObject *self)
}
}

template <binary_op_quad_def sleef_op, binary_op_longdouble_def longdouble_op>
static PyObject *
quad_ternary_power_func(PyObject *op1, PyObject *op2, PyObject *mod)
{
if (mod != Py_None) {
PyErr_SetString(PyExc_TypeError,
"pow() 3rd argument not allowed unless all arguments are integers");
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@ngoldbaum ngoldbaum Jan 9, 2026

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The way the if statement above is written, the bit starting with "unless" is incorrect unless I'm missing something. Not sure if you meant to implement what's in the error or if the error is wrong.

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@SwayamInSync SwayamInSync Jan 9, 2026

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Cpython's pow function take 3 args but the last arg is only valid if the inputs are integers, for float values it passes the py_none there.
quaddtype is floating-point so we anyways don't need that argument and if in case somebody explicitly called pow with a 3rd argument (mod) then it'll be a mistake and error out

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@SwayamInSync SwayamInSync Jan 9, 2026

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This is the standard behaviour so we are in this PR implementing the same

In [5]: pow(2.0, 1,2)
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
Cell In[5], line 1
----> 1 pow(2.0, 1,2)

TypeError: pow() 3rd argument not allowed unless all arguments are integers

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@SwayamInSync SwayamInSync Jan 9, 2026

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In quaddtype it should be as

In [2]: a = QuadPrecision("1")

In [3]: pow(a, 2)
Out[3]: QuadPrecision('1.0e+000', backend='sleef')

In [4]: pow(a, 2, 1)
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
Cell In[4], line 1
----> 1 pow(a, 2, 1)

TypeError: pow() 3rd argument not allowed unless all arguments are integers

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@ngoldbaum ngoldbaum Jan 9, 2026

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Thanks for explaining.

return NULL;
}
return quad_binary_func<sleef_op, longdouble_op>(op1, op2);
}

PyNumberMethods quad_as_scalar = {
.nb_add = (binaryfunc)quad_binary_func<quad_add, ld_add>,
.nb_subtract = (binaryfunc)quad_binary_func<quad_sub, ld_sub>,
.nb_multiply = (binaryfunc)quad_binary_func<quad_mul, ld_mul>,
.nb_power = (ternaryfunc)quad_binary_func<quad_pow, ld_pow>,
.nb_power = (ternaryfunc)quad_ternary_power_func<quad_pow, ld_pow>,
.nb_negative = (unaryfunc)quad_unary_func<quad_negative, ld_negative>,
.nb_positive = (unaryfunc)quad_unary_func<quad_positive, ld_positive>,
.nb_absolute = (unaryfunc)quad_unary_func<quad_absolute, ld_absolute>,
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11 changes: 10 additions & 1 deletion quaddtype/tests/test_quaddtype.py
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Original file line number Diff line number Diff line change
Expand Up @@ -5411,4 +5411,13 @@ def test_float_to_quad_sign_preserve(dtype, val):
if np.isnan(val):
assert np.isnan(result), f"NaN failed for {dtype}"
else:
assert result == val, f"{val} failed for {dtype}"
assert result == val, f"{val} failed for {dtype}"

@pytest.mark.parametrize("val, pow", [(2, 112), (2, -112), (10, 34), (10, -34)])
def test_quadprecision_large_exponents(val, pow):
mp.prec = 113
mp_value = mp.mpf(val) ** pow
value = QuadPrecision(val) ** pow
value_str = mp.nstr(mp.mpf(str(value)), 33)
expected_str = mp.nstr(mp_value, 33)
assert value_str == expected_str, f"QuadPrecision({val}) ** {pow} = {value_str}, expected {expected_str}"