[Python-checkins] r62414 - in python/trunk: Lib/test/test_math.py Modules/mathmodule.c
Benjamin Peterson
musiccomposition at gmail.com
Mon Apr 21 03:03:40 CEST 2008
Mark, can you fix the following compiler warning? (MacOS gcc)
py3k/Modules/mathmodule.c: In function 'math_pow':
py3k/Modules/mathmodule.c:597: warning: 'r' may be used uninitialized
in this function
On Sat, Apr 19, 2008 at 11:13 PM, mark.dickinson
<python-checkins at python.org> wrote:
> Author: mark.dickinson
> Date: Sun Apr 20 06:13:13 2008
> New Revision: 62414
>
> Log:
> Yet more explicit special case handling to make
> math.pow behave on alpha Tru64. All IEEE 754
> special values are now handled directly; only
> the finite**finite case is handled by libm.
>
>
> Modified:
> python/trunk/Lib/test/test_math.py
> python/trunk/Modules/mathmodule.c
>
> Modified: python/trunk/Lib/test/test_math.py
> ==============================================================================
> --- python/trunk/Lib/test/test_math.py (original)
> +++ python/trunk/Lib/test/test_math.py Sun Apr 20 06:13:13 2008
> @@ -498,6 +498,18 @@
> self.assertEqual(math.pow(-1.1, INF), INF)
> self.assertEqual(math.pow(-1.9, INF), INF)
>
> + # pow(x, y) should work for x negative, y an integer
> + self.ftest('(-2.)**3.', math.pow(-2.0, 3.0), -8.0)
> + self.ftest('(-2.)**2.', math.pow(-2.0, 2.0), 4.0)
> + self.ftest('(-2.)**1.', math.pow(-2.0, 1.0), -2.0)
> + self.ftest('(-2.)**0.', math.pow(-2.0, 0.0), 1.0)
> + self.ftest('(-2.)**-0.', math.pow(-2.0, -0.0), 1.0)
> + self.ftest('(-2.)**-1.', math.pow(-2.0, -1.0), -0.5)
> + self.ftest('(-2.)**-2.', math.pow(-2.0, -2.0), 0.25)
> + self.ftest('(-2.)**-3.', math.pow(-2.0, -3.0), -0.125)
> + self.assertRaises(ValueError, math.pow, -2.0, -0.5)
> + self.assertRaises(ValueError, math.pow, -2.0, 0.5)
> +
> # the following tests have been commented out since they don't
> # really belong here: the implementation of ** for floats is
> # independent of the implemention of math.pow
>
> Modified: python/trunk/Modules/mathmodule.c
> ==============================================================================
> --- python/trunk/Modules/mathmodule.c (original)
> +++ python/trunk/Modules/mathmodule.c Sun Apr 20 06:13:13 2008
> @@ -522,7 +522,7 @@
> {
> PyObject *ox, *oy;
> double r, x, y;
> - int y_is_odd;
> + int odd_y;
>
> if (! PyArg_UnpackTuple(args, "pow", 2, 2, &ox, &oy))
> return NULL;
> @@ -531,53 +531,61 @@
> if ((x == -1.0 || y == -1.0) && PyErr_Occurred())
> return NULL;
>
> - /* deal directly with various special cases, to cope with problems on
> - various platforms whose semantics don't exactly match C99 */
> -
> - /* 1**x, x**0, and (-1)**(+-infinity) return 1., even if x is NaN or
> - an infinity. */
> - if (x == 1. || y == 0. || (x == -1. && Py_IS_INFINITY(y)))
> - return PyFloat_FromDouble(1.);
> - /* otherwise, return a NaN if either input was a NaN */
> - if (Py_IS_NAN(x))
> - return PyFloat_FromDouble(x);
> - if (Py_IS_NAN(y))
> - return PyFloat_FromDouble(y);
> - /* inf ** (nonzero, non-NaN) is one of +-0, +-infinity */
> - if (Py_IS_INFINITY(x) && !Py_IS_NAN(y)) {
> - y_is_odd = Py_IS_FINITE(y) && fmod(fabs(y), 2.0) == 1.0;
> - if (y > 0.)
> - r = y_is_odd ? x : fabs(x);
> - else
> - r = y_is_odd ? copysign(0., x) : 0.;
> - return PyFloat_FromDouble(r);
> + /* deal directly with IEEE specials, to cope with problems on various
> + platforms whose semantics don't exactly match C99 */
> + if (!Py_IS_FINITE(x) || !Py_IS_FINITE(y)) {
> + errno = 0;
> + if (Py_IS_NAN(x))
> + r = y == 0. ? 1. : x; /* NaN**0 = 1 */
> + else if (Py_IS_NAN(y))
> + r = x == 1. ? 1. : y; /* 1**NaN = 1 */
> + else if (Py_IS_INFINITY(x)) {
> + odd_y = Py_IS_FINITE(y) && fmod(fabs(y), 2.0) == 1.0;
> + if (y > 0.)
> + r = odd_y ? x : fabs(x);
> + else if (y == 0.)
> + r = 1.;
> + else /* y < 0. */
> + r = odd_y ? copysign(0., x) : 0.;
> + }
> + else if (Py_IS_INFINITY(y)) {
> + if (fabs(x) == 1.0)
> + r = 1.;
> + else if (y > 0. && fabs(x) > 1.0)
> + r = y;
> + else if (y < 0. && fabs(x) < 1.0) {
> + r = -y; /* result is +inf */
> + if (x == 0.) /* 0**-inf: divide-by-zero */
> + errno = EDOM;
> + }
> + else
> + r = 0.;
> + }
> }
> -
> - errno = 0;
> - PyFPE_START_PROTECT("in math_pow", return 0);
> - r = pow(x, y);
> - PyFPE_END_PROTECT(r);
> - if (Py_IS_NAN(r)) {
> - errno = EDOM;
> - }
> - /* an infinite result arises either from:
> -
> - (A) (+/-0.)**negative,
> - (B) overflow of x**y with both x and y finite (and x nonzero)
> - (C) (+/-inf)**positive, or
> - (D) x**inf with |x| > 1, or x**-inf with |x| < 1.
> -
> - In case (A) we want ValueError to be raised. In case (B)
> - OverflowError should be raised. In cases (C) and (D) the infinite
> - result should be returned.
> - */
> - else if (Py_IS_INFINITY(r)) {
> - if (x == 0.)
> - errno = EDOM;
> - else if (Py_IS_FINITE(x) && Py_IS_FINITE(y))
> - errno = ERANGE;
> - else
> - errno = 0;
> + else {
> + /* let libm handle finite**finite */
> + errno = 0;
> + PyFPE_START_PROTECT("in math_pow", return 0);
> + r = pow(x, y);
> + PyFPE_END_PROTECT(r);
> + /* a NaN result should arise only from (-ve)**(finite
> + non-integer); in this case we want to raise ValueError. */
> + if (!Py_IS_FINITE(r)) {
> + if (Py_IS_NAN(r)) {
> + errno = EDOM;
> + }
> + /*
> + an infinite result here arises either from:
> + (A) (+/-0.)**negative (-> divide-by-zero)
> + (B) overflow of x**y with x and y finite
> + */
> + else if (Py_IS_INFINITY(r)) {
> + if (x == 0.)
> + errno = EDOM;
> + else
> + errno = ERANGE;
> + }
> + }
> }
>
> if (errno && is_error(r))
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--
Cheers,
Benjamin Peterson
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