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gh-117999: Fix small integer powers of complex numbers #124243

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gh-117999: Fix small integer powers of complex numbers #124243

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f2280be
gh-117999: Fix small integer powers of complex numbers
serhiy-storchaka Sep 19, 2024
5b5320a
Merge branch 'main' into complex_powi
serhiy-storchaka Nov 26, 2024
1304423
Polish tests.
serhiy-storchaka Nov 26, 2024
bc4adfd
Remove unrelated change.
serhiy-storchaka Nov 26, 2024
4b8535d
Merge branch 'main' into complex_powi
serhiy-storchaka Dec 12, 2024
e876273
Add more tests.
serhiy-storchaka Dec 12, 2024
bb748c7
Merge branch 'main' into complex_powi
serhiy-storchaka Feb 4, 2025
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Merge branch 'main' into complex_powi
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@serhiy-storchaka
serhiy-storchaka committed Nov 26, 2024
commit 5b5320ada8ff8fc4f3ba24018b20a94b429d0456
60 changes: 30 additions & 30 deletions Objects/complexobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -190,18 +190,31 @@ _Py_c_quot(Py_complex a, Py_complex b)

return r;
}

Py_complex
_Py_dc_quot(double a, Py_complex b)
_Py_cr_quot(Py_complex a, double b)
{
/* Divide a real number by a complex number.
* Same as _Py_c_quot(), but without imaginary part.
*/
Py_complex r; /* the result */
const double abs_breal = b.real < 0 ? -b.real : b.real;
const double abs_bimag = b.imag < 0 ? -b.imag : b.imag;
Py_complex r = a;
if (b) {
r.real /= b;
r.imag /= b;
}
else {
errno = EDOM;
r.real = r.imag = 0.0;
}
return r;
}

/* an equivalent of _Py_c_quot() function, when 1st argument is real */
Py_complex
_Py_rc_quot(double a, Py_complex b)
{
Py_complex r;
const double abs_breal = b.real < 0 ? -b.real : b.real;
const double abs_bimag = b.imag < 0 ? -b.imag : b.imag;

if (abs_breal >= abs_bimag) {
/* divide tops and bottom by b.real */
if (abs_breal == 0.0) {
errno = EDOM;
r.real = r.imag = 0.0;
Expand All @@ -210,40 +223,27 @@ _Py_dc_quot(double a, Py_complex b)
const double ratio = b.imag / b.real;
const double denom = b.real + b.imag * ratio;
r.real = a / denom;
r.imag = (- a * ratio) / denom;
r.imag = (-a * ratio) / denom;
}
}
else if (abs_bimag >= abs_breal) {
/* divide tops and bottom by b.imag */
const double ratio = b.real / b.imag;
const double denom = b.real * ratio + b.imag;
assert(b.imag != 0.0);
r.real = (a * ratio) / denom;
r.imag = (-a) / denom;
}
else {
/* At least one of b.real or b.imag is a NaN */
r.real = r.imag = Py_NAN;
}

/* Recover infinities and zeros that computed as nan+nanj. See e.g.
the C11, Annex G.5.2, routine _Cdivd(). */
if (isnan(r.real) && isnan(r.imag)) {
if (isinf(a)
&& isfinite(b.real) && isfinite(b.imag))
{
const double x = copysign(isinf(a) ? 1.0 : 0.0, a);
r.real = Py_INFINITY * (x*b.real);
r.imag = Py_INFINITY * (- x*b.imag);
}
else if ((isinf(abs_breal) || isinf(abs_bimag))
&& isfinite(a))
{
const double x = copysign(isinf(b.real) ? 1.0 : 0.0, b.real);
const double y = copysign(isinf(b.imag) ? 1.0 : 0.0, b.imag);
r.real = 0.0 * (a*x);
r.imag = 0.0 * (-a*y);
}
if (isnan(r.real) && isnan(r.imag) && isfinite(a)
&& (isinf(abs_breal) || isinf(abs_bimag)))
{
const double x = copysign(isinf(b.real) ? 1.0 : 0.0, b.real);
const double y = copysign(isinf(b.imag) ? 1.0 : 0.0, b.imag);
r.real = 0.0 * (a*x);
r.imag = 0.0 * (-a*y);
}

return r;
Expand Down Expand Up @@ -314,7 +314,7 @@ c_powi(Py_complex x, long n)
if (n > 0)
return c_powu(x, n);
else if (n < 0)
return _Py_dc_quot(1.0, c_powu(x, -n));
return _Py_rc_quot(1.0, c_powu(x, -n));
else
return c_1;
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@picnixz picnixz Aug 18, 2025

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Took me a while to remember that this was 1 + 0j (maybe rename that variable in a separate issue, e.g., ONE_AS_COMPLEX).

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@skirpichev skirpichev Aug 19, 2025

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This now used just in one place. If we need this branch - it's better to inline struct value here.

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@picnixz picnixz Aug 19, 2025

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If this is the case, then yes, let's inline it.

}
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