[Python-checkins] r75117 - in python/trunk: Doc/library/math.rst Lib/test/math_testcases.txt Lib/test/test_math.py Misc/NEWS Modules/mathmodule.c
mark.dickinson
python-checkins at python.org
Mon Sep 28 20:54:55 CEST 2009
Author: mark.dickinson
Date: Mon Sep 28 20:54:55 2009
New Revision: 75117
Log:
Issue #3366: Add gamma function to math module.
(lgamma, erf and erfc to follow).
Added:
python/trunk/Lib/test/math_testcases.txt
Modified:
python/trunk/Doc/library/math.rst
python/trunk/Lib/test/test_math.py
python/trunk/Misc/NEWS
python/trunk/Modules/mathmodule.c
Modified: python/trunk/Doc/library/math.rst
==============================================================================
--- python/trunk/Doc/library/math.rst (original)
+++ python/trunk/Doc/library/math.rst Mon Sep 28 20:54:55 2009
@@ -308,6 +308,16 @@
Return the hyperbolic tangent of *x*.
+Special functions
+-----------------
+
+.. function:: gamma(x)
+
+ Return the Gamma function at *x*.
+
+ .. versionadded:: 2.7
+
+
Constants
---------
Added: python/trunk/Lib/test/math_testcases.txt
==============================================================================
--- (empty file)
+++ python/trunk/Lib/test/math_testcases.txt Mon Sep 28 20:54:55 2009
@@ -0,0 +1,146 @@
+-- Testcases for functions in math.
+--
+-- Each line takes the form:
+--
+-- <testid> <function> <input_value> -> <output_value> <flags>
+--
+-- where:
+--
+-- <testid> is a short name identifying the test,
+--
+-- <function> is the function to be tested (exp, cos, asinh, ...),
+--
+-- <input_value> is a string representing a floating-point value
+--
+-- <output_value> is the expected (ideal) output value, again
+-- represented as a string.
+--
+-- <flags> is a list of the floating-point flags required by C99
+--
+-- The possible flags are:
+--
+-- divide-by-zero : raised when a finite input gives a
+-- mathematically infinite result.
+--
+-- overflow : raised when a finite input gives a finite result that
+-- is too large to fit in the usual range of an IEEE 754 double.
+--
+-- invalid : raised for invalid inputs (e.g., sqrt(-1))
+--
+-- ignore-sign : indicates that the sign of the result is
+-- unspecified; e.g., if the result is given as inf,
+-- then both -inf and inf should be accepted as correct.
+--
+-- Flags may appear in any order.
+--
+-- Lines beginning with '--' (like this one) start a comment, and are
+-- ignored. Blank lines, or lines containing only whitespace, are also
+-- ignored.
+
+-- Many of the values below were computed with the help of
+-- version 2.4 of the MPFR library for multiple-precision
+-- floating-point computations with correct rounding. All output
+-- values in this file are (modulo yet-to-be-discovered bugs)
+-- correctly rounded, provided that each input and output decimal
+-- floating-point value below is interpreted as a representation of
+-- the corresponding nearest IEEE 754 double-precision value. See the
+-- MPFR homepage at http://www.mpfr.org for more information about the
+-- MPFR project.
+
+---------------------------
+-- gamma: Gamma function --
+---------------------------
+
+-- special values
+gam0000 gamma 0.0 -> inf divide-by-zero
+gam0001 gamma -0.0 -> -inf divide-by-zero
+gam0002 gamma inf -> inf
+gam0003 gamma -inf -> nan invalid
+gam0004 gamma nan -> nan
+
+-- negative integers inputs are invalid
+gam0010 gamma -1 -> nan invalid
+gam0011 gamma -2 -> nan invalid
+gam0012 gamma -1e16 -> nan invalid
+gam0013 gamma -1e300 -> nan invalid
+
+-- small positive integers give factorials
+gam0020 gamma 1 -> 1
+gam0021 gamma 2 -> 1
+gam0022 gamma 3 -> 2
+gam0023 gamma 4 -> 6
+gam0024 gamma 5 -> 24
+gam0025 gamma 6 -> 120
+
+-- half integers
+gam0030 gamma 0.5 -> 1.7724538509055161
+gam0031 gamma 1.5 -> 0.88622692545275805
+gam0032 gamma 2.5 -> 1.3293403881791370
+gam0033 gamma 3.5 -> 3.3233509704478426
+gam0034 gamma -0.5 -> -3.5449077018110322
+gam0035 gamma -1.5 -> 2.3632718012073548
+gam0036 gamma -2.5 -> -0.94530872048294190
+gam0037 gamma -3.5 -> 0.27008820585226911
+
+-- values near 0
+gam0040 gamma 0.1 -> 9.5135076986687306
+gam0041 gamma 0.01 -> 99.432585119150602
+gam0042 gamma 1e-8 -> 99999999.422784343
+gam0043 gamma 1e-16 -> 10000000000000000
+gam0044 gamma 1e-30 -> 9.9999999999999988e+29
+gam0045 gamma 1e-160 -> 1.0000000000000000e+160
+gam0046 gamma 1e-308 -> 1.0000000000000000e+308
+gam0047 gamma 5.6e-309 -> 1.7857142857142848e+308
+gam0048 gamma 5.5e-309 -> inf overflow
+gam0049 gamma 1e-309 -> inf overflow
+gam0050 gamma 1e-323 -> inf overflow
+gam0051 gamma 5e-324 -> inf overflow
+gam0060 gamma -0.1 -> -10.686287021193193
+gam0061 gamma -0.01 -> -100.58719796441078
+gam0062 gamma -1e-8 -> -100000000.57721567
+gam0063 gamma -1e-16 -> -10000000000000000
+gam0064 gamma -1e-30 -> -9.9999999999999988e+29
+gam0065 gamma -1e-160 -> -1.0000000000000000e+160
+gam0066 gamma -1e-308 -> -1.0000000000000000e+308
+gam0067 gamma -5.6e-309 -> -1.7857142857142848e+308
+gam0068 gamma -5.5e-309 -> -inf overflow
+gam0069 gamma -1e-309 -> -inf overflow
+gam0070 gamma -1e-323 -> -inf overflow
+gam0071 gamma -5e-324 -> -inf overflow
+
+-- values near negative integers
+gam0080 gamma -0.99999999999999989 -> -9007199254740992.0
+gam0081 gamma -1.0000000000000002 -> 4503599627370495.5
+gam0082 gamma -1.9999999999999998 -> 2251799813685248.5
+gam0083 gamma -2.0000000000000004 -> -1125899906842623.5
+gam0084 gamma -100.00000000000001 -> -7.5400833348831090e-145
+gam0085 gamma -99.999999999999986 -> 7.5400833348840962e-145
+
+-- large inputs
+gam0100 gamma 170 -> 4.2690680090047051e+304
+gam0101 gamma 171 -> 7.2574156153079990e+306
+gam0102 gamma 171.624 -> 1.7942117599248104e+308
+gam0103 gamma 171.625 -> inf overflow
+gam0104 gamma 172 -> inf overflow
+gam0105 gamma 2000 -> inf overflow
+gam0106 gamma 1.7e308 -> inf overflow
+
+-- inputs for which gamma(x) is tiny
+gam0120 gamma -100.5 -> -3.3536908198076787e-159
+gam0121 gamma -160.5 -> -5.2555464470078293e-286
+gam0122 gamma -170.5 -> -3.3127395215386074e-308
+gam0123 gamma -171.5 -> 1.9316265431711902e-310
+gam0124 gamma -176.5 -> -1.1956388629358166e-321
+gam0125 gamma -177.5 -> 4.9406564584124654e-324
+gam0126 gamma -178.5 -> -0.0
+gam0127 gamma -179.5 -> 0.0
+gam0128 gamma -201.0001 -> 0.0
+gam0129 gamma -202.9999 -> -0.0
+gam0130 gamma -1000.5 -> -0.0
+gam0131 gamma -1000000000.3 -> -0.0
+gam0132 gamma -4503599627370495.5 -> 0.0
+
+-- inputs that cause problems for the standard reflection formula,
+-- thanks to loss of accuracy in 1-x
+gam0140 gamma -63.349078729022985 -> 4.1777971677761880e-88
+gam0141 gamma -127.45117632943295 -> 1.1831110896236810e-214
Modified: python/trunk/Lib/test/test_math.py
==============================================================================
--- python/trunk/Lib/test/test_math.py (original)
+++ python/trunk/Lib/test/test_math.py Mon Sep 28 20:54:55 2009
@@ -7,6 +7,7 @@
import os
import sys
import random
+import struct
eps = 1E-05
NAN = float('nan')
@@ -29,8 +30,50 @@
else:
file = __file__
test_dir = os.path.dirname(file) or os.curdir
+math_testcases = os.path.join(test_dir, 'math_testcases.txt')
test_file = os.path.join(test_dir, 'cmath_testcases.txt')
+def to_ulps(x):
+ """Convert a non-NaN float x to an integer, in such a way that
+ adjacent floats are converted to adjacent integers. Then
+ abs(ulps(x) - ulps(y)) gives the difference in ulps between two
+ floats.
+
+ The results from this function will only make sense on platforms
+ where C doubles are represented in IEEE 754 binary64 format.
+
+ """
+ n = struct.unpack('q', struct.pack('<d', x))[0]
+ if n < 0:
+ n = ~(n+2**63)
+ return n
+
+
+def parse_mtestfile(fname):
+ """Parse a file with test values
+
+ -- starts a comment
+ blank lines, or lines containing only a comment, are ignored
+ other lines are expected to have the form
+ id fn arg -> expected [flag]*
+
+ """
+ with open(fname) as fp:
+ for line in fp:
+ # strip comments, and skip blank lines
+ if '--' in line:
+ line = line[:line.index('--')]
+ if not line.strip():
+ continue
+
+ lhs, rhs = line.split('->')
+ id, fn, arg = lhs.split()
+ rhs_pieces = rhs.split()
+ exp = rhs_pieces[0]
+ flags = rhs_pieces[1:]
+
+ yield (id, fn, float(arg), float(exp), flags)
+
def parse_testfile(fname):
"""Parse a file with test values
@@ -887,6 +930,51 @@
self.fail(message)
self.ftest("%s:%s(%r)" % (id, fn, ar), result, er)
+ @unittest.skipUnless(float.__getformat__("double").startswith("IEEE"),
+ "test requires IEEE 754 doubles")
+ def test_mtestfile(self):
+ ALLOWED_ERROR = 20 # permitted error, in ulps
+ fail_fmt = "{}:{}({!r}): expected {!r}, got {!r}"
+
+ failures = []
+ for id, fn, arg, expected, flags in parse_mtestfile(math_testcases):
+ func = getattr(math, fn)
+
+ if 'invalid' in flags or 'divide-by-zero' in flags:
+ expected = 'ValueError'
+ elif 'overflow' in flags:
+ expected = 'OverflowError'
+
+ try:
+ got = func(arg)
+ except ValueError:
+ got = 'ValueError'
+ except OverflowError:
+ got = 'OverflowError'
+
+ diff_ulps = None
+ if isinstance(got, float) and isinstance(expected, float):
+ if math.isnan(expected) and math.isnan(got):
+ continue
+ if not math.isnan(expected) and not math.isnan(got):
+ diff_ulps = to_ulps(expected) - to_ulps(got)
+ if diff_ulps <= ALLOWED_ERROR:
+ continue
+
+ if isinstance(got, str) and isinstance(expected, str):
+ if got == expected:
+ continue
+
+ fail_msg = fail_fmt.format(id, fn, arg, expected, got)
+ if diff_ulps is not None:
+ fail_msg += ' ({} ulps)'.format(diff_ulps)
+ failures.append(fail_msg)
+
+ if failures:
+ self.fail('Failures in test_mtestfile:\n ' +
+ '\n '.join(failures))
+
+
def test_main():
from doctest import DocFileSuite
suite = unittest.TestSuite()
Modified: python/trunk/Misc/NEWS
==============================================================================
--- python/trunk/Misc/NEWS (original)
+++ python/trunk/Misc/NEWS Mon Sep 28 20:54:55 2009
@@ -1341,6 +1341,8 @@
Extension Modules
-----------------
+- Issue #3366: Add gamma function to math module.
+
- Issue #6823: Allow time.strftime() to accept a tuple with a isdst field
outside of the range of [-1, 1] by normalizing the value to within that
range.
Modified: python/trunk/Modules/mathmodule.c
==============================================================================
--- python/trunk/Modules/mathmodule.c (original)
+++ python/trunk/Modules/mathmodule.c Mon Sep 28 20:54:55 2009
@@ -60,44 +60,265 @@
extern double copysign(double, double);
#endif
-/* Call is_error when errno != 0, and where x is the result libm
- * returned. is_error will usually set up an exception and return
- * true (1), but may return false (0) without setting up an exception.
- */
-static int
-is_error(double x)
+/*
+ sin(pi*x), giving accurate results for all finite x (especially x
+ integral or close to an integer). This is here for use in the
+ reflection formula for the gamma function. It conforms to IEEE
+ 754-2008 for finite arguments, but not for infinities or nans.
+*/
+
+static const double pi = 3.141592653589793238462643383279502884197;
+
+static double
+sinpi(double x)
{
- int result = 1; /* presumption of guilt */
- assert(errno); /* non-zero errno is a precondition for calling */
- if (errno == EDOM)
- PyErr_SetString(PyExc_ValueError, "math domain error");
+ double y, r;
+ int n;
+ /* this function should only ever be called for finite arguments */
+ assert(Py_IS_FINITE(x));
+ y = fmod(fabs(x), 2.0);
+ n = (int)round(2.0*y);
+ assert(0 <= n && n <= 4);
+ switch (n) {
+ case 0:
+ r = sin(pi*y);
+ break;
+ case 1:
+ r = cos(pi*(y-0.5));
+ break;
+ case 2:
+ /* N.B. -sin(pi*(y-1.0)) is *not* equivalent: it would give
+ -0.0 instead of 0.0 when y == 1.0. */
+ r = sin(pi*(1.0-y));
+ break;
+ case 3:
+ r = -cos(pi*(y-1.5));
+ break;
+ case 4:
+ r = sin(pi*(y-2.0));
+ break;
+ default:
+ assert(0); /* should never get here */
+ r = -1.23e200; /* silence gcc warning */
+ }
+ return copysign(1.0, x)*r;
+}
+
+/* Implementation of the real gamma function. In extensive but non-exhaustive
+ random tests, this function proved accurate to within <= 10 ulps across the
+ entire float domain. Note that accuracy may depend on the quality of the
+ system math functions, the pow function in particular. Special cases
+ follow C99 annex F. The parameters and method are tailored to platforms
+ whose double format is the IEEE 754 binary64 format.
+
+ Method: for x > 0.0 we use the Lanczos approximation with parameters N=13
+ and g=6.024680040776729583740234375; these parameters are amongst those
+ used by the Boost library. Following Boost (again), we re-express the
+ Lanczos sum as a rational function, and compute it that way. The
+ coefficients below were computed independently using MPFR, and have been
+ double-checked against the coefficients in the Boost source code.
+
+ For x < 0.0 we use the reflection formula.
+
+ There's one minor tweak that deserves explanation: Lanczos' formula for
+ Gamma(x) involves computing pow(x+g-0.5, x-0.5) / exp(x+g-0.5). For many x
+ values, x+g-0.5 can be represented exactly. However, in cases where it
+ can't be represented exactly the small error in x+g-0.5 can be magnified
+ significantly by the pow and exp calls, especially for large x. A cheap
+ correction is to multiply by (1 + e*g/(x+g-0.5)), where e is the error
+ involved in the computation of x+g-0.5 (that is, e = computed value of
+ x+g-0.5 - exact value of x+g-0.5). Here's the proof:
+
+ Correction factor
+ -----------------
+ Write x+g-0.5 = y-e, where y is exactly representable as an IEEE 754
+ double, and e is tiny. Then:
+
+ pow(x+g-0.5,x-0.5)/exp(x+g-0.5) = pow(y-e, x-0.5)/exp(y-e)
+ = pow(y, x-0.5)/exp(y) * C,
+
+ where the correction_factor C is given by
+
+ C = pow(1-e/y, x-0.5) * exp(e)
+
+ Since e is tiny, pow(1-e/y, x-0.5) ~ 1-(x-0.5)*e/y, and exp(x) ~ 1+e, so:
+
+ C ~ (1-(x-0.5)*e/y) * (1+e) ~ 1 + e*(y-(x-0.5))/y
+
+ But y-(x-0.5) = g+e, and g+e ~ g. So we get C ~ 1 + e*g/y, and
+
+ pow(x+g-0.5,x-0.5)/exp(x+g-0.5) ~ pow(y, x-0.5)/exp(y) * (1 + e*g/y),
+
+ Note that for accuracy, when computing r*C it's better to do
- else if (errno == ERANGE) {
- /* ANSI C generally requires libm functions to set ERANGE
- * on overflow, but also generally *allows* them to set
- * ERANGE on underflow too. There's no consistency about
- * the latter across platforms.
- * Alas, C99 never requires that errno be set.
- * Here we suppress the underflow errors (libm functions
- * should return a zero on underflow, and +- HUGE_VAL on
- * overflow, so testing the result for zero suffices to
- * distinguish the cases).
- *
- * On some platforms (Ubuntu/ia64) it seems that errno can be
- * set to ERANGE for subnormal results that do *not* underflow
- * to zero. So to be safe, we'll ignore ERANGE whenever the
- * function result is less than one in absolute value.
- */
- if (fabs(x) < 1.0)
- result = 0;
- else
- PyErr_SetString(PyExc_OverflowError,
- "math range error");
+ r + e*g/y*r;
+
+ than
+
+ r * (1 + e*g/y);
+
+ since the addition in the latter throws away most of the bits of
+ information in e*g/y.
+*/
+
+#define LANCZOS_N 13
+static const double lanczos_g = 6.024680040776729583740234375;
+static const double lanczos_g_minus_half = 5.524680040776729583740234375;
+static const double lanczos_num_coeffs[LANCZOS_N] = {
+ 23531376880.410759688572007674451636754734846804940,
+ 42919803642.649098768957899047001988850926355848959,
+ 35711959237.355668049440185451547166705960488635843,
+ 17921034426.037209699919755754458931112671403265390,
+ 6039542586.3520280050642916443072979210699388420708,
+ 1439720407.3117216736632230727949123939715485786772,
+ 248874557.86205415651146038641322942321632125127801,
+ 31426415.585400194380614231628318205362874684987640,
+ 2876370.6289353724412254090516208496135991145378768,
+ 186056.26539522349504029498971604569928220784236328,
+ 8071.6720023658162106380029022722506138218516325024,
+ 210.82427775157934587250973392071336271166969580291,
+ 2.5066282746310002701649081771338373386264310793408
+};
+
+/* denominator is x*(x+1)*...*(x+LANCZOS_N-2) */
+static const double lanczos_den_coeffs[LANCZOS_N] = {
+ 0.0, 39916800.0, 120543840.0, 150917976.0, 105258076.0, 45995730.0,
+ 13339535.0, 2637558.0, 357423.0, 32670.0, 1925.0, 66.0, 1.0};
+
+/* gamma values for small positive integers, 1 though NGAMMA_INTEGRAL */
+#define NGAMMA_INTEGRAL 23
+static const double gamma_integral[NGAMMA_INTEGRAL] = {
+ 1.0, 1.0, 2.0, 6.0, 24.0, 120.0, 720.0, 5040.0, 40320.0, 362880.0,
+ 3628800.0, 39916800.0, 479001600.0, 6227020800.0, 87178291200.0,
+ 1307674368000.0, 20922789888000.0, 355687428096000.0,
+ 6402373705728000.0, 121645100408832000.0, 2432902008176640000.0,
+ 51090942171709440000.0, 1124000727777607680000.0,
+};
+
+/* Lanczos' sum L_g(x), for positive x */
+
+static double
+lanczos_sum(double x)
+{
+ double num = 0.0, den = 0.0;
+ int i;
+ assert(x > 0.0);
+ /* evaluate the rational function lanczos_sum(x). For large
+ x, the obvious algorithm risks overflow, so we instead
+ rescale the denominator and numerator of the rational
+ function by x**(1-LANCZOS_N) and treat this as a
+ rational function in 1/x. This also reduces the error for
+ larger x values. The choice of cutoff point (5.0 below) is
+ somewhat arbitrary; in tests, smaller cutoff values than
+ this resulted in lower accuracy. */
+ if (x < 5.0) {
+ for (i = LANCZOS_N; --i >= 0; ) {
+ num = num * x + lanczos_num_coeffs[i];
+ den = den * x + lanczos_den_coeffs[i];
+ }
}
- else
- /* Unexpected math error */
- PyErr_SetFromErrno(PyExc_ValueError);
- return result;
+ else {
+ for (i = 0; i < LANCZOS_N; i++) {
+ num = num / x + lanczos_num_coeffs[i];
+ den = den / x + lanczos_den_coeffs[i];
+ }
+ }
+ return num/den;
+}
+
+static double
+m_tgamma(double x)
+{
+ double absx, r, y, z, sqrtpow;
+
+ /* special cases */
+ if (!Py_IS_FINITE(x)) {
+ if (Py_IS_NAN(x) || x > 0.0)
+ return x; /* tgamma(nan) = nan, tgamma(inf) = inf */
+ else {
+ errno = EDOM;
+ return Py_NAN; /* tgamma(-inf) = nan, invalid */
+ }
+ }
+ if (x == 0.0) {
+ errno = EDOM;
+ return 1.0/x; /* tgamma(+-0.0) = +-inf, divide-by-zero */
+ }
+
+ /* integer arguments */
+ if (x == floor(x)) {
+ if (x < 0.0) {
+ errno = EDOM; /* tgamma(n) = nan, invalid for */
+ return Py_NAN; /* negative integers n */
+ }
+ if (x <= NGAMMA_INTEGRAL)
+ return gamma_integral[(int)x - 1];
+ }
+ absx = fabs(x);
+
+ /* tiny arguments: tgamma(x) ~ 1/x for x near 0 */
+ if (absx < 1e-20) {
+ r = 1.0/x;
+ if (Py_IS_INFINITY(r))
+ errno = ERANGE;
+ return r;
+ }
+
+ /* large arguments: assuming IEEE 754 doubles, tgamma(x) overflows for
+ x > 200, and underflows to +-0.0 for x < -200, not a negative
+ integer. */
+ if (absx > 200.0) {
+ if (x < 0.0) {
+ return 0.0/sinpi(x);
+ }
+ else {
+ errno = ERANGE;
+ return Py_HUGE_VAL;
+ }
+ }
+
+ y = absx + lanczos_g_minus_half;
+ /* compute error in sum */
+ if (absx > lanczos_g_minus_half) {
+ /* note: the correction can be foiled by an optimizing
+ compiler that (incorrectly) thinks that an expression like
+ a + b - a - b can be optimized to 0.0. This shouldn't
+ happen in a standards-conforming compiler. */
+ double q = y - absx;
+ z = q - lanczos_g_minus_half;
+ }
+ else {
+ double q = y - lanczos_g_minus_half;
+ z = q - absx;
+ }
+ z = z * lanczos_g / y;
+ if (x < 0.0) {
+ r = -pi / sinpi(absx) / absx * exp(y) / lanczos_sum(absx);
+ r -= z * r;
+ if (absx < 140.0) {
+ r /= pow(y, absx - 0.5);
+ }
+ else {
+ sqrtpow = pow(y, absx / 2.0 - 0.25);
+ r /= sqrtpow;
+ r /= sqrtpow;
+ }
+ }
+ else {
+ r = lanczos_sum(absx) / exp(y);
+ r += z * r;
+ if (absx < 140.0) {
+ r *= pow(y, absx - 0.5);
+ }
+ else {
+ sqrtpow = pow(y, absx / 2.0 - 0.25);
+ r *= sqrtpow;
+ r *= sqrtpow;
+ }
+ }
+ if (Py_IS_INFINITY(r))
+ errno = ERANGE;
+ return r;
}
/*
@@ -188,6 +409,46 @@
}
+/* Call is_error when errno != 0, and where x is the result libm
+ * returned. is_error will usually set up an exception and return
+ * true (1), but may return false (0) without setting up an exception.
+ */
+static int
+is_error(double x)
+{
+ int result = 1; /* presumption of guilt */
+ assert(errno); /* non-zero errno is a precondition for calling */
+ if (errno == EDOM)
+ PyErr_SetString(PyExc_ValueError, "math domain error");
+
+ else if (errno == ERANGE) {
+ /* ANSI C generally requires libm functions to set ERANGE
+ * on overflow, but also generally *allows* them to set
+ * ERANGE on underflow too. There's no consistency about
+ * the latter across platforms.
+ * Alas, C99 never requires that errno be set.
+ * Here we suppress the underflow errors (libm functions
+ * should return a zero on underflow, and +- HUGE_VAL on
+ * overflow, so testing the result for zero suffices to
+ * distinguish the cases).
+ *
+ * On some platforms (Ubuntu/ia64) it seems that errno can be
+ * set to ERANGE for subnormal results that do *not* underflow
+ * to zero. So to be safe, we'll ignore ERANGE whenever the
+ * function result is less than one in absolute value.
+ */
+ if (fabs(x) < 1.0)
+ result = 0;
+ else
+ PyErr_SetString(PyExc_OverflowError,
+ "math range error");
+ }
+ else
+ /* Unexpected math error */
+ PyErr_SetFromErrno(PyExc_ValueError);
+ return result;
+}
+
/*
math_1 is used to wrap a libm function f that takes a double
arguments and returns a double.
@@ -247,6 +508,26 @@
return PyFloat_FromDouble(r);
}
+/* variant of math_1, to be used when the function being wrapped is known to
+ set errno properly (that is, errno = EDOM for invalid or divide-by-zero,
+ errno = ERANGE for overflow). */
+
+static PyObject *
+math_1a(PyObject *arg, double (*func) (double))
+{
+ double x, r;
+ x = PyFloat_AsDouble(arg);
+ if (x == -1.0 && PyErr_Occurred())
+ return NULL;
+ errno = 0;
+ PyFPE_START_PROTECT("in math_1a", return 0);
+ r = (*func)(x);
+ PyFPE_END_PROTECT(r);
+ if (errno && is_error(r))
+ return NULL;
+ return PyFloat_FromDouble(r);
+}
+
/*
math_2 is used to wrap a libm function f that takes two double
arguments and returns a double.
@@ -313,6 +594,12 @@
}\
PyDoc_STRVAR(math_##funcname##_doc, docstring);
+#define FUNC1A(funcname, func, docstring) \
+ static PyObject * math_##funcname(PyObject *self, PyObject *args) { \
+ return math_1a(args, func); \
+ }\
+ PyDoc_STRVAR(math_##funcname##_doc, docstring);
+
#define FUNC2(funcname, func, docstring) \
static PyObject * math_##funcname(PyObject *self, PyObject *args) { \
return math_2(args, func, #funcname); \
@@ -350,6 +637,8 @@
FUNC1(floor, floor, 0,
"floor(x)\n\nReturn the floor of x as a float.\n"
"This is the largest integral value <= x.")
+FUNC1A(gamma, m_tgamma,
+ "gamma(x)\n\nGamma function at x.")
FUNC1(log1p, log1p, 1,
"log1p(x)\n\nReturn the natural logarithm of 1+x (base e).\n\
The result is computed in a way which is accurate for x near zero.")
@@ -1077,6 +1366,7 @@
{"fmod", math_fmod, METH_VARARGS, math_fmod_doc},
{"frexp", math_frexp, METH_O, math_frexp_doc},
{"fsum", math_fsum, METH_O, math_fsum_doc},
+ {"gamma", math_gamma, METH_O, math_gamma_doc},
{"hypot", math_hypot, METH_VARARGS, math_hypot_doc},
{"isinf", math_isinf, METH_O, math_isinf_doc},
{"isnan", math_isnan, METH_O, math_isnan_doc},
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