mirror of
https://github.com/python/cpython.git
synced 2024-12-18 22:34:08 +08:00
8f9f8d612a
I expect the system libc to use more accurate functions than Python. The GNU libc uses for example FYL2X and FYL2XP1 hardware instructions on Intel FPU.
2007 lines
64 KiB
C
2007 lines
64 KiB
C
/* Math module -- standard C math library functions, pi and e */
|
|
|
|
/* Here are some comments from Tim Peters, extracted from the
|
|
discussion attached to http://bugs.python.org/issue1640. They
|
|
describe the general aims of the math module with respect to
|
|
special values, IEEE-754 floating-point exceptions, and Python
|
|
exceptions.
|
|
|
|
These are the "spirit of 754" rules:
|
|
|
|
1. If the mathematical result is a real number, but of magnitude too
|
|
large to approximate by a machine float, overflow is signaled and the
|
|
result is an infinity (with the appropriate sign).
|
|
|
|
2. If the mathematical result is a real number, but of magnitude too
|
|
small to approximate by a machine float, underflow is signaled and the
|
|
result is a zero (with the appropriate sign).
|
|
|
|
3. At a singularity (a value x such that the limit of f(y) as y
|
|
approaches x exists and is an infinity), "divide by zero" is signaled
|
|
and the result is an infinity (with the appropriate sign). This is
|
|
complicated a little by that the left-side and right-side limits may
|
|
not be the same; e.g., 1/x approaches +inf or -inf as x approaches 0
|
|
from the positive or negative directions. In that specific case, the
|
|
sign of the zero determines the result of 1/0.
|
|
|
|
4. At a point where a function has no defined result in the extended
|
|
reals (i.e., the reals plus an infinity or two), invalid operation is
|
|
signaled and a NaN is returned.
|
|
|
|
And these are what Python has historically /tried/ to do (but not
|
|
always successfully, as platform libm behavior varies a lot):
|
|
|
|
For #1, raise OverflowError.
|
|
|
|
For #2, return a zero (with the appropriate sign if that happens by
|
|
accident ;-)).
|
|
|
|
For #3 and #4, raise ValueError. It may have made sense to raise
|
|
Python's ZeroDivisionError in #3, but historically that's only been
|
|
raised for division by zero and mod by zero.
|
|
|
|
*/
|
|
|
|
/*
|
|
In general, on an IEEE-754 platform the aim is to follow the C99
|
|
standard, including Annex 'F', whenever possible. Where the
|
|
standard recommends raising the 'divide-by-zero' or 'invalid'
|
|
floating-point exceptions, Python should raise a ValueError. Where
|
|
the standard recommends raising 'overflow', Python should raise an
|
|
OverflowError. In all other circumstances a value should be
|
|
returned.
|
|
*/
|
|
|
|
#include "Python.h"
|
|
#include "_math.h"
|
|
|
|
/*
|
|
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 const double sqrtpi = 1.772453850905516027298167483341145182798;
|
|
static const double logpi = 1.144729885849400174143427351353058711647;
|
|
|
|
static double
|
|
sinpi(double x)
|
|
{
|
|
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
|
|
|
|
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 {
|
|
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;
|
|
}
|
|
|
|
/*
|
|
lgamma: natural log of the absolute value of the Gamma function.
|
|
For large arguments, Lanczos' formula works extremely well here.
|
|
*/
|
|
|
|
static double
|
|
m_lgamma(double x)
|
|
{
|
|
double r, absx;
|
|
|
|
/* special cases */
|
|
if (!Py_IS_FINITE(x)) {
|
|
if (Py_IS_NAN(x))
|
|
return x; /* lgamma(nan) = nan */
|
|
else
|
|
return Py_HUGE_VAL; /* lgamma(+-inf) = +inf */
|
|
}
|
|
|
|
/* integer arguments */
|
|
if (x == floor(x) && x <= 2.0) {
|
|
if (x <= 0.0) {
|
|
errno = EDOM; /* lgamma(n) = inf, divide-by-zero for */
|
|
return Py_HUGE_VAL; /* integers n <= 0 */
|
|
}
|
|
else {
|
|
return 0.0; /* lgamma(1) = lgamma(2) = 0.0 */
|
|
}
|
|
}
|
|
|
|
absx = fabs(x);
|
|
/* tiny arguments: lgamma(x) ~ -log(fabs(x)) for small x */
|
|
if (absx < 1e-20)
|
|
return -log(absx);
|
|
|
|
/* Lanczos' formula. We could save a fraction of a ulp in accuracy by
|
|
having a second set of numerator coefficients for lanczos_sum that
|
|
absorbed the exp(-lanczos_g) term, and throwing out the lanczos_g
|
|
subtraction below; it's probably not worth it. */
|
|
r = log(lanczos_sum(absx)) - lanczos_g;
|
|
r += (absx - 0.5) * (log(absx + lanczos_g - 0.5) - 1);
|
|
if (x < 0.0)
|
|
/* Use reflection formula to get value for negative x. */
|
|
r = logpi - log(fabs(sinpi(absx))) - log(absx) - r;
|
|
if (Py_IS_INFINITY(r))
|
|
errno = ERANGE;
|
|
return r;
|
|
}
|
|
|
|
/*
|
|
Implementations of the error function erf(x) and the complementary error
|
|
function erfc(x).
|
|
|
|
Method: following 'Numerical Recipes' by Flannery, Press et. al. (2nd ed.,
|
|
Cambridge University Press), we use a series approximation for erf for
|
|
small x, and a continued fraction approximation for erfc(x) for larger x;
|
|
combined with the relations erf(-x) = -erf(x) and erfc(x) = 1.0 - erf(x),
|
|
this gives us erf(x) and erfc(x) for all x.
|
|
|
|
The series expansion used is:
|
|
|
|
erf(x) = x*exp(-x*x)/sqrt(pi) * [
|
|
2/1 + 4/3 x**2 + 8/15 x**4 + 16/105 x**6 + ...]
|
|
|
|
The coefficient of x**(2k-2) here is 4**k*factorial(k)/factorial(2*k).
|
|
This series converges well for smallish x, but slowly for larger x.
|
|
|
|
The continued fraction expansion used is:
|
|
|
|
erfc(x) = x*exp(-x*x)/sqrt(pi) * [1/(0.5 + x**2 -) 0.5/(2.5 + x**2 - )
|
|
3.0/(4.5 + x**2 - ) 7.5/(6.5 + x**2 - ) ...]
|
|
|
|
after the first term, the general term has the form:
|
|
|
|
k*(k-0.5)/(2*k+0.5 + x**2 - ...).
|
|
|
|
This expansion converges fast for larger x, but convergence becomes
|
|
infinitely slow as x approaches 0.0. The (somewhat naive) continued
|
|
fraction evaluation algorithm used below also risks overflow for large x;
|
|
but for large x, erfc(x) == 0.0 to within machine precision. (For
|
|
example, erfc(30.0) is approximately 2.56e-393).
|
|
|
|
Parameters: use series expansion for abs(x) < ERF_SERIES_CUTOFF and
|
|
continued fraction expansion for ERF_SERIES_CUTOFF <= abs(x) <
|
|
ERFC_CONTFRAC_CUTOFF. ERFC_SERIES_TERMS and ERFC_CONTFRAC_TERMS are the
|
|
numbers of terms to use for the relevant expansions. */
|
|
|
|
#define ERF_SERIES_CUTOFF 1.5
|
|
#define ERF_SERIES_TERMS 25
|
|
#define ERFC_CONTFRAC_CUTOFF 30.0
|
|
#define ERFC_CONTFRAC_TERMS 50
|
|
|
|
/*
|
|
Error function, via power series.
|
|
|
|
Given a finite float x, return an approximation to erf(x).
|
|
Converges reasonably fast for small x.
|
|
*/
|
|
|
|
static double
|
|
m_erf_series(double x)
|
|
{
|
|
double x2, acc, fk, result;
|
|
int i, saved_errno;
|
|
|
|
x2 = x * x;
|
|
acc = 0.0;
|
|
fk = (double)ERF_SERIES_TERMS + 0.5;
|
|
for (i = 0; i < ERF_SERIES_TERMS; i++) {
|
|
acc = 2.0 + x2 * acc / fk;
|
|
fk -= 1.0;
|
|
}
|
|
/* Make sure the exp call doesn't affect errno;
|
|
see m_erfc_contfrac for more. */
|
|
saved_errno = errno;
|
|
result = acc * x * exp(-x2) / sqrtpi;
|
|
errno = saved_errno;
|
|
return result;
|
|
}
|
|
|
|
/*
|
|
Complementary error function, via continued fraction expansion.
|
|
|
|
Given a positive float x, return an approximation to erfc(x). Converges
|
|
reasonably fast for x large (say, x > 2.0), and should be safe from
|
|
overflow if x and nterms are not too large. On an IEEE 754 machine, with x
|
|
<= 30.0, we're safe up to nterms = 100. For x >= 30.0, erfc(x) is smaller
|
|
than the smallest representable nonzero float. */
|
|
|
|
static double
|
|
m_erfc_contfrac(double x)
|
|
{
|
|
double x2, a, da, p, p_last, q, q_last, b, result;
|
|
int i, saved_errno;
|
|
|
|
if (x >= ERFC_CONTFRAC_CUTOFF)
|
|
return 0.0;
|
|
|
|
x2 = x*x;
|
|
a = 0.0;
|
|
da = 0.5;
|
|
p = 1.0; p_last = 0.0;
|
|
q = da + x2; q_last = 1.0;
|
|
for (i = 0; i < ERFC_CONTFRAC_TERMS; i++) {
|
|
double temp;
|
|
a += da;
|
|
da += 2.0;
|
|
b = da + x2;
|
|
temp = p; p = b*p - a*p_last; p_last = temp;
|
|
temp = q; q = b*q - a*q_last; q_last = temp;
|
|
}
|
|
/* Issue #8986: On some platforms, exp sets errno on underflow to zero;
|
|
save the current errno value so that we can restore it later. */
|
|
saved_errno = errno;
|
|
result = p / q * x * exp(-x2) / sqrtpi;
|
|
errno = saved_errno;
|
|
return result;
|
|
}
|
|
|
|
/* Error function erf(x), for general x */
|
|
|
|
static double
|
|
m_erf(double x)
|
|
{
|
|
double absx, cf;
|
|
|
|
if (Py_IS_NAN(x))
|
|
return x;
|
|
absx = fabs(x);
|
|
if (absx < ERF_SERIES_CUTOFF)
|
|
return m_erf_series(x);
|
|
else {
|
|
cf = m_erfc_contfrac(absx);
|
|
return x > 0.0 ? 1.0 - cf : cf - 1.0;
|
|
}
|
|
}
|
|
|
|
/* Complementary error function erfc(x), for general x. */
|
|
|
|
static double
|
|
m_erfc(double x)
|
|
{
|
|
double absx, cf;
|
|
|
|
if (Py_IS_NAN(x))
|
|
return x;
|
|
absx = fabs(x);
|
|
if (absx < ERF_SERIES_CUTOFF)
|
|
return 1.0 - m_erf_series(x);
|
|
else {
|
|
cf = m_erfc_contfrac(absx);
|
|
return x > 0.0 ? cf : 2.0 - cf;
|
|
}
|
|
}
|
|
|
|
/*
|
|
wrapper for atan2 that deals directly with special cases before
|
|
delegating to the platform libm for the remaining cases. This
|
|
is necessary to get consistent behaviour across platforms.
|
|
Windows, FreeBSD and alpha Tru64 are amongst platforms that don't
|
|
always follow C99.
|
|
*/
|
|
|
|
static double
|
|
m_atan2(double y, double x)
|
|
{
|
|
if (Py_IS_NAN(x) || Py_IS_NAN(y))
|
|
return Py_NAN;
|
|
if (Py_IS_INFINITY(y)) {
|
|
if (Py_IS_INFINITY(x)) {
|
|
if (copysign(1., x) == 1.)
|
|
/* atan2(+-inf, +inf) == +-pi/4 */
|
|
return copysign(0.25*Py_MATH_PI, y);
|
|
else
|
|
/* atan2(+-inf, -inf) == +-pi*3/4 */
|
|
return copysign(0.75*Py_MATH_PI, y);
|
|
}
|
|
/* atan2(+-inf, x) == +-pi/2 for finite x */
|
|
return copysign(0.5*Py_MATH_PI, y);
|
|
}
|
|
if (Py_IS_INFINITY(x) || y == 0.) {
|
|
if (copysign(1., x) == 1.)
|
|
/* atan2(+-y, +inf) = atan2(+-0, +x) = +-0. */
|
|
return copysign(0., y);
|
|
else
|
|
/* atan2(+-y, -inf) = atan2(+-0., -x) = +-pi. */
|
|
return copysign(Py_MATH_PI, y);
|
|
}
|
|
return atan2(y, x);
|
|
}
|
|
|
|
/*
|
|
Various platforms (Solaris, OpenBSD) do nonstandard things for log(0),
|
|
log(-ve), log(NaN). Here are wrappers for log and log10 that deal with
|
|
special values directly, passing positive non-special values through to
|
|
the system log/log10.
|
|
*/
|
|
|
|
static double
|
|
m_log(double x)
|
|
{
|
|
if (Py_IS_FINITE(x)) {
|
|
if (x > 0.0)
|
|
return log(x);
|
|
errno = EDOM;
|
|
if (x == 0.0)
|
|
return -Py_HUGE_VAL; /* log(0) = -inf */
|
|
else
|
|
return Py_NAN; /* log(-ve) = nan */
|
|
}
|
|
else if (Py_IS_NAN(x))
|
|
return x; /* log(nan) = nan */
|
|
else if (x > 0.0)
|
|
return x; /* log(inf) = inf */
|
|
else {
|
|
errno = EDOM;
|
|
return Py_NAN; /* log(-inf) = nan */
|
|
}
|
|
}
|
|
|
|
/*
|
|
log2: log to base 2.
|
|
|
|
Uses an algorithm that should:
|
|
|
|
(a) produce exact results for powers of 2, and
|
|
(b) give a monotonic log2 (for positive finite floats),
|
|
assuming that the system log is monotonic.
|
|
*/
|
|
|
|
static double
|
|
m_log2(double x)
|
|
{
|
|
if (!Py_IS_FINITE(x)) {
|
|
if (Py_IS_NAN(x))
|
|
return x; /* log2(nan) = nan */
|
|
else if (x > 0.0)
|
|
return x; /* log2(+inf) = +inf */
|
|
else {
|
|
errno = EDOM;
|
|
return Py_NAN; /* log2(-inf) = nan, invalid-operation */
|
|
}
|
|
}
|
|
|
|
if (x > 0.0) {
|
|
#ifdef HAVE_LOG2
|
|
return log2(x);
|
|
#else
|
|
double m;
|
|
int e;
|
|
m = frexp(x, &e);
|
|
/* We want log2(m * 2**e) == log(m) / log(2) + e. Care is needed when
|
|
* x is just greater than 1.0: in that case e is 1, log(m) is negative,
|
|
* and we get significant cancellation error from the addition of
|
|
* log(m) / log(2) to e. The slight rewrite of the expression below
|
|
* avoids this problem.
|
|
*/
|
|
if (x >= 1.0) {
|
|
return log(2.0 * m) / log(2.0) + (e - 1);
|
|
}
|
|
else {
|
|
return log(m) / log(2.0) + e;
|
|
}
|
|
#endif
|
|
}
|
|
else if (x == 0.0) {
|
|
errno = EDOM;
|
|
return -Py_HUGE_VAL; /* log2(0) = -inf, divide-by-zero */
|
|
}
|
|
else {
|
|
errno = EDOM;
|
|
return Py_NAN; /* log2(-inf) = nan, invalid-operation */
|
|
}
|
|
}
|
|
|
|
static double
|
|
m_log10(double x)
|
|
{
|
|
if (Py_IS_FINITE(x)) {
|
|
if (x > 0.0)
|
|
return log10(x);
|
|
errno = EDOM;
|
|
if (x == 0.0)
|
|
return -Py_HUGE_VAL; /* log10(0) = -inf */
|
|
else
|
|
return Py_NAN; /* log10(-ve) = nan */
|
|
}
|
|
else if (Py_IS_NAN(x))
|
|
return x; /* log10(nan) = nan */
|
|
else if (x > 0.0)
|
|
return x; /* log10(inf) = inf */
|
|
else {
|
|
errno = EDOM;
|
|
return Py_NAN; /* log10(-inf) = nan */
|
|
}
|
|
}
|
|
|
|
|
|
/* 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.
|
|
|
|
The error reporting follows these rules, which are designed to do
|
|
the right thing on C89/C99 platforms and IEEE 754/non IEEE 754
|
|
platforms.
|
|
|
|
- a NaN result from non-NaN inputs causes ValueError to be raised
|
|
- an infinite result from finite inputs causes OverflowError to be
|
|
raised if can_overflow is 1, or raises ValueError if can_overflow
|
|
is 0.
|
|
- if the result is finite and errno == EDOM then ValueError is
|
|
raised
|
|
- if the result is finite and nonzero and errno == ERANGE then
|
|
OverflowError is raised
|
|
|
|
The last rule is used to catch overflow on platforms which follow
|
|
C89 but for which HUGE_VAL is not an infinity.
|
|
|
|
For the majority of one-argument functions these rules are enough
|
|
to ensure that Python's functions behave as specified in 'Annex F'
|
|
of the C99 standard, with the 'invalid' and 'divide-by-zero'
|
|
floating-point exceptions mapping to Python's ValueError and the
|
|
'overflow' floating-point exception mapping to OverflowError.
|
|
math_1 only works for functions that don't have singularities *and*
|
|
the possibility of overflow; fortunately, that covers everything we
|
|
care about right now.
|
|
*/
|
|
|
|
static PyObject *
|
|
math_1_to_whatever(PyObject *arg, double (*func) (double),
|
|
PyObject *(*from_double_func) (double),
|
|
int can_overflow)
|
|
{
|
|
double x, r;
|
|
x = PyFloat_AsDouble(arg);
|
|
if (x == -1.0 && PyErr_Occurred())
|
|
return NULL;
|
|
errno = 0;
|
|
PyFPE_START_PROTECT("in math_1", return 0);
|
|
r = (*func)(x);
|
|
PyFPE_END_PROTECT(r);
|
|
if (Py_IS_NAN(r) && !Py_IS_NAN(x)) {
|
|
PyErr_SetString(PyExc_ValueError,
|
|
"math domain error"); /* invalid arg */
|
|
return NULL;
|
|
}
|
|
if (Py_IS_INFINITY(r) && Py_IS_FINITE(x)) {
|
|
if (can_overflow)
|
|
PyErr_SetString(PyExc_OverflowError,
|
|
"math range error"); /* overflow */
|
|
else
|
|
PyErr_SetString(PyExc_ValueError,
|
|
"math domain error"); /* singularity */
|
|
return NULL;
|
|
}
|
|
if (Py_IS_FINITE(r) && errno && is_error(r))
|
|
/* this branch unnecessary on most platforms */
|
|
return NULL;
|
|
|
|
return (*from_double_func)(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.
|
|
|
|
The error reporting follows these rules, which are designed to do
|
|
the right thing on C89/C99 platforms and IEEE 754/non IEEE 754
|
|
platforms.
|
|
|
|
- a NaN result from non-NaN inputs causes ValueError to be raised
|
|
- an infinite result from finite inputs causes OverflowError to be
|
|
raised.
|
|
- if the result is finite and errno == EDOM then ValueError is
|
|
raised
|
|
- if the result is finite and nonzero and errno == ERANGE then
|
|
OverflowError is raised
|
|
|
|
The last rule is used to catch overflow on platforms which follow
|
|
C89 but for which HUGE_VAL is not an infinity.
|
|
|
|
For most two-argument functions (copysign, fmod, hypot, atan2)
|
|
these rules are enough to ensure that Python's functions behave as
|
|
specified in 'Annex F' of the C99 standard, with the 'invalid' and
|
|
'divide-by-zero' floating-point exceptions mapping to Python's
|
|
ValueError and the 'overflow' floating-point exception mapping to
|
|
OverflowError.
|
|
*/
|
|
|
|
static PyObject *
|
|
math_1(PyObject *arg, double (*func) (double), int can_overflow)
|
|
{
|
|
return math_1_to_whatever(arg, func, PyFloat_FromDouble, can_overflow);
|
|
}
|
|
|
|
static PyObject *
|
|
math_1_to_int(PyObject *arg, double (*func) (double), int can_overflow)
|
|
{
|
|
return math_1_to_whatever(arg, func, PyLong_FromDouble, can_overflow);
|
|
}
|
|
|
|
static PyObject *
|
|
math_2(PyObject *args, double (*func) (double, double), char *funcname)
|
|
{
|
|
PyObject *ox, *oy;
|
|
double x, y, r;
|
|
if (! PyArg_UnpackTuple(args, funcname, 2, 2, &ox, &oy))
|
|
return NULL;
|
|
x = PyFloat_AsDouble(ox);
|
|
y = PyFloat_AsDouble(oy);
|
|
if ((x == -1.0 || y == -1.0) && PyErr_Occurred())
|
|
return NULL;
|
|
errno = 0;
|
|
PyFPE_START_PROTECT("in math_2", return 0);
|
|
r = (*func)(x, y);
|
|
PyFPE_END_PROTECT(r);
|
|
if (Py_IS_NAN(r)) {
|
|
if (!Py_IS_NAN(x) && !Py_IS_NAN(y))
|
|
errno = EDOM;
|
|
else
|
|
errno = 0;
|
|
}
|
|
else if (Py_IS_INFINITY(r)) {
|
|
if (Py_IS_FINITE(x) && Py_IS_FINITE(y))
|
|
errno = ERANGE;
|
|
else
|
|
errno = 0;
|
|
}
|
|
if (errno && is_error(r))
|
|
return NULL;
|
|
else
|
|
return PyFloat_FromDouble(r);
|
|
}
|
|
|
|
#define FUNC1(funcname, func, can_overflow, docstring) \
|
|
static PyObject * math_##funcname(PyObject *self, PyObject *args) { \
|
|
return math_1(args, func, can_overflow); \
|
|
}\
|
|
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); \
|
|
}\
|
|
PyDoc_STRVAR(math_##funcname##_doc, docstring);
|
|
|
|
FUNC1(acos, acos, 0,
|
|
"acos(x)\n\nReturn the arc cosine (measured in radians) of x.")
|
|
FUNC1(acosh, m_acosh, 0,
|
|
"acosh(x)\n\nReturn the hyperbolic arc cosine (measured in radians) of x.")
|
|
FUNC1(asin, asin, 0,
|
|
"asin(x)\n\nReturn the arc sine (measured in radians) of x.")
|
|
FUNC1(asinh, m_asinh, 0,
|
|
"asinh(x)\n\nReturn the hyperbolic arc sine (measured in radians) of x.")
|
|
FUNC1(atan, atan, 0,
|
|
"atan(x)\n\nReturn the arc tangent (measured in radians) of x.")
|
|
FUNC2(atan2, m_atan2,
|
|
"atan2(y, x)\n\nReturn the arc tangent (measured in radians) of y/x.\n"
|
|
"Unlike atan(y/x), the signs of both x and y are considered.")
|
|
FUNC1(atanh, m_atanh, 0,
|
|
"atanh(x)\n\nReturn the hyperbolic arc tangent (measured in radians) of x.")
|
|
|
|
static PyObject * math_ceil(PyObject *self, PyObject *number) {
|
|
static PyObject *ceil_str = NULL;
|
|
PyObject *method, *result;
|
|
|
|
method = _PyObject_LookupSpecial(number, "__ceil__", &ceil_str);
|
|
if (method == NULL) {
|
|
if (PyErr_Occurred())
|
|
return NULL;
|
|
return math_1_to_int(number, ceil, 0);
|
|
}
|
|
result = PyObject_CallFunctionObjArgs(method, NULL);
|
|
Py_DECREF(method);
|
|
return result;
|
|
}
|
|
|
|
PyDoc_STRVAR(math_ceil_doc,
|
|
"ceil(x)\n\nReturn the ceiling of x as an int.\n"
|
|
"This is the smallest integral value >= x.");
|
|
|
|
FUNC2(copysign, copysign,
|
|
"copysign(x, y)\n\nReturn x with the sign of y.")
|
|
FUNC1(cos, cos, 0,
|
|
"cos(x)\n\nReturn the cosine of x (measured in radians).")
|
|
FUNC1(cosh, cosh, 1,
|
|
"cosh(x)\n\nReturn the hyperbolic cosine of x.")
|
|
FUNC1A(erf, m_erf,
|
|
"erf(x)\n\nError function at x.")
|
|
FUNC1A(erfc, m_erfc,
|
|
"erfc(x)\n\nComplementary error function at x.")
|
|
FUNC1(exp, exp, 1,
|
|
"exp(x)\n\nReturn e raised to the power of x.")
|
|
FUNC1(expm1, m_expm1, 1,
|
|
"expm1(x)\n\nReturn exp(x)-1.\n"
|
|
"This function avoids the loss of precision involved in the direct "
|
|
"evaluation of exp(x)-1 for small x.")
|
|
FUNC1(fabs, fabs, 0,
|
|
"fabs(x)\n\nReturn the absolute value of the float x.")
|
|
|
|
static PyObject * math_floor(PyObject *self, PyObject *number) {
|
|
static PyObject *floor_str = NULL;
|
|
PyObject *method, *result;
|
|
|
|
method = _PyObject_LookupSpecial(number, "__floor__", &floor_str);
|
|
if (method == NULL) {
|
|
if (PyErr_Occurred())
|
|
return NULL;
|
|
return math_1_to_int(number, floor, 0);
|
|
}
|
|
result = PyObject_CallFunctionObjArgs(method, NULL);
|
|
Py_DECREF(method);
|
|
return result;
|
|
}
|
|
|
|
PyDoc_STRVAR(math_floor_doc,
|
|
"floor(x)\n\nReturn the floor of x as an int.\n"
|
|
"This is the largest integral value <= x.");
|
|
|
|
FUNC1A(gamma, m_tgamma,
|
|
"gamma(x)\n\nGamma function at x.")
|
|
FUNC1A(lgamma, m_lgamma,
|
|
"lgamma(x)\n\nNatural logarithm of absolute value of Gamma function at x.")
|
|
FUNC1(log1p, m_log1p, 0,
|
|
"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.")
|
|
FUNC1(sin, sin, 0,
|
|
"sin(x)\n\nReturn the sine of x (measured in radians).")
|
|
FUNC1(sinh, sinh, 1,
|
|
"sinh(x)\n\nReturn the hyperbolic sine of x.")
|
|
FUNC1(sqrt, sqrt, 0,
|
|
"sqrt(x)\n\nReturn the square root of x.")
|
|
FUNC1(tan, tan, 0,
|
|
"tan(x)\n\nReturn the tangent of x (measured in radians).")
|
|
FUNC1(tanh, tanh, 0,
|
|
"tanh(x)\n\nReturn the hyperbolic tangent of x.")
|
|
|
|
/* Precision summation function as msum() by Raymond Hettinger in
|
|
<http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/393090>,
|
|
enhanced with the exact partials sum and roundoff from Mark
|
|
Dickinson's post at <http://bugs.python.org/file10357/msum4.py>.
|
|
See those links for more details, proofs and other references.
|
|
|
|
Note 1: IEEE 754R floating point semantics are assumed,
|
|
but the current implementation does not re-establish special
|
|
value semantics across iterations (i.e. handling -Inf + Inf).
|
|
|
|
Note 2: No provision is made for intermediate overflow handling;
|
|
therefore, sum([1e+308, 1e-308, 1e+308]) returns 1e+308 while
|
|
sum([1e+308, 1e+308, 1e-308]) raises an OverflowError due to the
|
|
overflow of the first partial sum.
|
|
|
|
Note 3: The intermediate values lo, yr, and hi are declared volatile so
|
|
aggressive compilers won't algebraically reduce lo to always be exactly 0.0.
|
|
Also, the volatile declaration forces the values to be stored in memory as
|
|
regular doubles instead of extended long precision (80-bit) values. This
|
|
prevents double rounding because any addition or subtraction of two doubles
|
|
can be resolved exactly into double-sized hi and lo values. As long as the
|
|
hi value gets forced into a double before yr and lo are computed, the extra
|
|
bits in downstream extended precision operations (x87 for example) will be
|
|
exactly zero and therefore can be losslessly stored back into a double,
|
|
thereby preventing double rounding.
|
|
|
|
Note 4: A similar implementation is in Modules/cmathmodule.c.
|
|
Be sure to update both when making changes.
|
|
|
|
Note 5: The signature of math.fsum() differs from __builtin__.sum()
|
|
because the start argument doesn't make sense in the context of
|
|
accurate summation. Since the partials table is collapsed before
|
|
returning a result, sum(seq2, start=sum(seq1)) may not equal the
|
|
accurate result returned by sum(itertools.chain(seq1, seq2)).
|
|
*/
|
|
|
|
#define NUM_PARTIALS 32 /* initial partials array size, on stack */
|
|
|
|
/* Extend the partials array p[] by doubling its size. */
|
|
static int /* non-zero on error */
|
|
_fsum_realloc(double **p_ptr, Py_ssize_t n,
|
|
double *ps, Py_ssize_t *m_ptr)
|
|
{
|
|
void *v = NULL;
|
|
Py_ssize_t m = *m_ptr;
|
|
|
|
m += m; /* double */
|
|
if (n < m && m < (PY_SSIZE_T_MAX / sizeof(double))) {
|
|
double *p = *p_ptr;
|
|
if (p == ps) {
|
|
v = PyMem_Malloc(sizeof(double) * m);
|
|
if (v != NULL)
|
|
memcpy(v, ps, sizeof(double) * n);
|
|
}
|
|
else
|
|
v = PyMem_Realloc(p, sizeof(double) * m);
|
|
}
|
|
if (v == NULL) { /* size overflow or no memory */
|
|
PyErr_SetString(PyExc_MemoryError, "math.fsum partials");
|
|
return 1;
|
|
}
|
|
*p_ptr = (double*) v;
|
|
*m_ptr = m;
|
|
return 0;
|
|
}
|
|
|
|
/* Full precision summation of a sequence of floats.
|
|
|
|
def msum(iterable):
|
|
partials = [] # sorted, non-overlapping partial sums
|
|
for x in iterable:
|
|
i = 0
|
|
for y in partials:
|
|
if abs(x) < abs(y):
|
|
x, y = y, x
|
|
hi = x + y
|
|
lo = y - (hi - x)
|
|
if lo:
|
|
partials[i] = lo
|
|
i += 1
|
|
x = hi
|
|
partials[i:] = [x]
|
|
return sum_exact(partials)
|
|
|
|
Rounded x+y stored in hi with the roundoff stored in lo. Together hi+lo
|
|
are exactly equal to x+y. The inner loop applies hi/lo summation to each
|
|
partial so that the list of partial sums remains exact.
|
|
|
|
Sum_exact() adds the partial sums exactly and correctly rounds the final
|
|
result (using the round-half-to-even rule). The items in partials remain
|
|
non-zero, non-special, non-overlapping and strictly increasing in
|
|
magnitude, but possibly not all having the same sign.
|
|
|
|
Depends on IEEE 754 arithmetic guarantees and half-even rounding.
|
|
*/
|
|
|
|
static PyObject*
|
|
math_fsum(PyObject *self, PyObject *seq)
|
|
{
|
|
PyObject *item, *iter, *sum = NULL;
|
|
Py_ssize_t i, j, n = 0, m = NUM_PARTIALS;
|
|
double x, y, t, ps[NUM_PARTIALS], *p = ps;
|
|
double xsave, special_sum = 0.0, inf_sum = 0.0;
|
|
volatile double hi, yr, lo;
|
|
|
|
iter = PyObject_GetIter(seq);
|
|
if (iter == NULL)
|
|
return NULL;
|
|
|
|
PyFPE_START_PROTECT("fsum", Py_DECREF(iter); return NULL)
|
|
|
|
for(;;) { /* for x in iterable */
|
|
assert(0 <= n && n <= m);
|
|
assert((m == NUM_PARTIALS && p == ps) ||
|
|
(m > NUM_PARTIALS && p != NULL));
|
|
|
|
item = PyIter_Next(iter);
|
|
if (item == NULL) {
|
|
if (PyErr_Occurred())
|
|
goto _fsum_error;
|
|
break;
|
|
}
|
|
x = PyFloat_AsDouble(item);
|
|
Py_DECREF(item);
|
|
if (PyErr_Occurred())
|
|
goto _fsum_error;
|
|
|
|
xsave = x;
|
|
for (i = j = 0; j < n; j++) { /* for y in partials */
|
|
y = p[j];
|
|
if (fabs(x) < fabs(y)) {
|
|
t = x; x = y; y = t;
|
|
}
|
|
hi = x + y;
|
|
yr = hi - x;
|
|
lo = y - yr;
|
|
if (lo != 0.0)
|
|
p[i++] = lo;
|
|
x = hi;
|
|
}
|
|
|
|
n = i; /* ps[i:] = [x] */
|
|
if (x != 0.0) {
|
|
if (! Py_IS_FINITE(x)) {
|
|
/* a nonfinite x could arise either as
|
|
a result of intermediate overflow, or
|
|
as a result of a nan or inf in the
|
|
summands */
|
|
if (Py_IS_FINITE(xsave)) {
|
|
PyErr_SetString(PyExc_OverflowError,
|
|
"intermediate overflow in fsum");
|
|
goto _fsum_error;
|
|
}
|
|
if (Py_IS_INFINITY(xsave))
|
|
inf_sum += xsave;
|
|
special_sum += xsave;
|
|
/* reset partials */
|
|
n = 0;
|
|
}
|
|
else if (n >= m && _fsum_realloc(&p, n, ps, &m))
|
|
goto _fsum_error;
|
|
else
|
|
p[n++] = x;
|
|
}
|
|
}
|
|
|
|
if (special_sum != 0.0) {
|
|
if (Py_IS_NAN(inf_sum))
|
|
PyErr_SetString(PyExc_ValueError,
|
|
"-inf + inf in fsum");
|
|
else
|
|
sum = PyFloat_FromDouble(special_sum);
|
|
goto _fsum_error;
|
|
}
|
|
|
|
hi = 0.0;
|
|
if (n > 0) {
|
|
hi = p[--n];
|
|
/* sum_exact(ps, hi) from the top, stop when the sum becomes
|
|
inexact. */
|
|
while (n > 0) {
|
|
x = hi;
|
|
y = p[--n];
|
|
assert(fabs(y) < fabs(x));
|
|
hi = x + y;
|
|
yr = hi - x;
|
|
lo = y - yr;
|
|
if (lo != 0.0)
|
|
break;
|
|
}
|
|
/* Make half-even rounding work across multiple partials.
|
|
Needed so that sum([1e-16, 1, 1e16]) will round-up the last
|
|
digit to two instead of down to zero (the 1e-16 makes the 1
|
|
slightly closer to two). With a potential 1 ULP rounding
|
|
error fixed-up, math.fsum() can guarantee commutativity. */
|
|
if (n > 0 && ((lo < 0.0 && p[n-1] < 0.0) ||
|
|
(lo > 0.0 && p[n-1] > 0.0))) {
|
|
y = lo * 2.0;
|
|
x = hi + y;
|
|
yr = x - hi;
|
|
if (y == yr)
|
|
hi = x;
|
|
}
|
|
}
|
|
sum = PyFloat_FromDouble(hi);
|
|
|
|
_fsum_error:
|
|
PyFPE_END_PROTECT(hi)
|
|
Py_DECREF(iter);
|
|
if (p != ps)
|
|
PyMem_Free(p);
|
|
return sum;
|
|
}
|
|
|
|
#undef NUM_PARTIALS
|
|
|
|
PyDoc_STRVAR(math_fsum_doc,
|
|
"fsum(iterable)\n\n\
|
|
Return an accurate floating point sum of values in the iterable.\n\
|
|
Assumes IEEE-754 floating point arithmetic.");
|
|
|
|
/* Return the smallest integer k such that n < 2**k, or 0 if n == 0.
|
|
* Equivalent to floor(lg(x))+1. Also equivalent to: bitwidth_of_type -
|
|
* count_leading_zero_bits(x)
|
|
*/
|
|
|
|
/* XXX: This routine does more or less the same thing as
|
|
* bits_in_digit() in Objects/longobject.c. Someday it would be nice to
|
|
* consolidate them. On BSD, there's a library function called fls()
|
|
* that we could use, and GCC provides __builtin_clz().
|
|
*/
|
|
|
|
static unsigned long
|
|
bit_length(unsigned long n)
|
|
{
|
|
unsigned long len = 0;
|
|
while (n != 0) {
|
|
++len;
|
|
n >>= 1;
|
|
}
|
|
return len;
|
|
}
|
|
|
|
static unsigned long
|
|
count_set_bits(unsigned long n)
|
|
{
|
|
unsigned long count = 0;
|
|
while (n != 0) {
|
|
++count;
|
|
n &= n - 1; /* clear least significant bit */
|
|
}
|
|
return count;
|
|
}
|
|
|
|
/* Divide-and-conquer factorial algorithm
|
|
*
|
|
* Based on the formula and psuedo-code provided at:
|
|
* http://www.luschny.de/math/factorial/binarysplitfact.html
|
|
*
|
|
* Faster algorithms exist, but they're more complicated and depend on
|
|
* a fast prime factorization algorithm.
|
|
*
|
|
* Notes on the algorithm
|
|
* ----------------------
|
|
*
|
|
* factorial(n) is written in the form 2**k * m, with m odd. k and m are
|
|
* computed separately, and then combined using a left shift.
|
|
*
|
|
* The function factorial_odd_part computes the odd part m (i.e., the greatest
|
|
* odd divisor) of factorial(n), using the formula:
|
|
*
|
|
* factorial_odd_part(n) =
|
|
*
|
|
* product_{i >= 0} product_{0 < j <= n / 2**i, j odd} j
|
|
*
|
|
* Example: factorial_odd_part(20) =
|
|
*
|
|
* (1) *
|
|
* (1) *
|
|
* (1 * 3 * 5) *
|
|
* (1 * 3 * 5 * 7 * 9)
|
|
* (1 * 3 * 5 * 7 * 9 * 11 * 13 * 15 * 17 * 19)
|
|
*
|
|
* Here i goes from large to small: the first term corresponds to i=4 (any
|
|
* larger i gives an empty product), and the last term corresponds to i=0.
|
|
* Each term can be computed from the last by multiplying by the extra odd
|
|
* numbers required: e.g., to get from the penultimate term to the last one,
|
|
* we multiply by (11 * 13 * 15 * 17 * 19).
|
|
*
|
|
* To see a hint of why this formula works, here are the same numbers as above
|
|
* but with the even parts (i.e., the appropriate powers of 2) included. For
|
|
* each subterm in the product for i, we multiply that subterm by 2**i:
|
|
*
|
|
* factorial(20) =
|
|
*
|
|
* (16) *
|
|
* (8) *
|
|
* (4 * 12 * 20) *
|
|
* (2 * 6 * 10 * 14 * 18) *
|
|
* (1 * 3 * 5 * 7 * 9 * 11 * 13 * 15 * 17 * 19)
|
|
*
|
|
* The factorial_partial_product function computes the product of all odd j in
|
|
* range(start, stop) for given start and stop. It's used to compute the
|
|
* partial products like (11 * 13 * 15 * 17 * 19) in the example above. It
|
|
* operates recursively, repeatedly splitting the range into two roughly equal
|
|
* pieces until the subranges are small enough to be computed using only C
|
|
* integer arithmetic.
|
|
*
|
|
* The two-valuation k (i.e., the exponent of the largest power of 2 dividing
|
|
* the factorial) is computed independently in the main math_factorial
|
|
* function. By standard results, its value is:
|
|
*
|
|
* two_valuation = n//2 + n//4 + n//8 + ....
|
|
*
|
|
* It can be shown (e.g., by complete induction on n) that two_valuation is
|
|
* equal to n - count_set_bits(n), where count_set_bits(n) gives the number of
|
|
* '1'-bits in the binary expansion of n.
|
|
*/
|
|
|
|
/* factorial_partial_product: Compute product(range(start, stop, 2)) using
|
|
* divide and conquer. Assumes start and stop are odd and stop > start.
|
|
* max_bits must be >= bit_length(stop - 2). */
|
|
|
|
static PyObject *
|
|
factorial_partial_product(unsigned long start, unsigned long stop,
|
|
unsigned long max_bits)
|
|
{
|
|
unsigned long midpoint, num_operands;
|
|
PyObject *left = NULL, *right = NULL, *result = NULL;
|
|
|
|
/* If the return value will fit an unsigned long, then we can
|
|
* multiply in a tight, fast loop where each multiply is O(1).
|
|
* Compute an upper bound on the number of bits required to store
|
|
* the answer.
|
|
*
|
|
* Storing some integer z requires floor(lg(z))+1 bits, which is
|
|
* conveniently the value returned by bit_length(z). The
|
|
* product x*y will require at most
|
|
* bit_length(x) + bit_length(y) bits to store, based
|
|
* on the idea that lg product = lg x + lg y.
|
|
*
|
|
* We know that stop - 2 is the largest number to be multiplied. From
|
|
* there, we have: bit_length(answer) <= num_operands *
|
|
* bit_length(stop - 2)
|
|
*/
|
|
|
|
num_operands = (stop - start) / 2;
|
|
/* The "num_operands <= 8 * SIZEOF_LONG" check guards against the
|
|
* unlikely case of an overflow in num_operands * max_bits. */
|
|
if (num_operands <= 8 * SIZEOF_LONG &&
|
|
num_operands * max_bits <= 8 * SIZEOF_LONG) {
|
|
unsigned long j, total;
|
|
for (total = start, j = start + 2; j < stop; j += 2)
|
|
total *= j;
|
|
return PyLong_FromUnsignedLong(total);
|
|
}
|
|
|
|
/* find midpoint of range(start, stop), rounded up to next odd number. */
|
|
midpoint = (start + num_operands) | 1;
|
|
left = factorial_partial_product(start, midpoint,
|
|
bit_length(midpoint - 2));
|
|
if (left == NULL)
|
|
goto error;
|
|
right = factorial_partial_product(midpoint, stop, max_bits);
|
|
if (right == NULL)
|
|
goto error;
|
|
result = PyNumber_Multiply(left, right);
|
|
|
|
error:
|
|
Py_XDECREF(left);
|
|
Py_XDECREF(right);
|
|
return result;
|
|
}
|
|
|
|
/* factorial_odd_part: compute the odd part of factorial(n). */
|
|
|
|
static PyObject *
|
|
factorial_odd_part(unsigned long n)
|
|
{
|
|
long i;
|
|
unsigned long v, lower, upper;
|
|
PyObject *partial, *tmp, *inner, *outer;
|
|
|
|
inner = PyLong_FromLong(1);
|
|
if (inner == NULL)
|
|
return NULL;
|
|
outer = inner;
|
|
Py_INCREF(outer);
|
|
|
|
upper = 3;
|
|
for (i = bit_length(n) - 2; i >= 0; i--) {
|
|
v = n >> i;
|
|
if (v <= 2)
|
|
continue;
|
|
lower = upper;
|
|
/* (v + 1) | 1 = least odd integer strictly larger than n / 2**i */
|
|
upper = (v + 1) | 1;
|
|
/* Here inner is the product of all odd integers j in the range (0,
|
|
n/2**(i+1)]. The factorial_partial_product call below gives the
|
|
product of all odd integers j in the range (n/2**(i+1), n/2**i]. */
|
|
partial = factorial_partial_product(lower, upper, bit_length(upper-2));
|
|
/* inner *= partial */
|
|
if (partial == NULL)
|
|
goto error;
|
|
tmp = PyNumber_Multiply(inner, partial);
|
|
Py_DECREF(partial);
|
|
if (tmp == NULL)
|
|
goto error;
|
|
Py_DECREF(inner);
|
|
inner = tmp;
|
|
/* Now inner is the product of all odd integers j in the range (0,
|
|
n/2**i], giving the inner product in the formula above. */
|
|
|
|
/* outer *= inner; */
|
|
tmp = PyNumber_Multiply(outer, inner);
|
|
if (tmp == NULL)
|
|
goto error;
|
|
Py_DECREF(outer);
|
|
outer = tmp;
|
|
}
|
|
|
|
goto done;
|
|
|
|
error:
|
|
Py_DECREF(outer);
|
|
done:
|
|
Py_DECREF(inner);
|
|
return outer;
|
|
}
|
|
|
|
/* Lookup table for small factorial values */
|
|
|
|
static const unsigned long SmallFactorials[] = {
|
|
1, 1, 2, 6, 24, 120, 720, 5040, 40320,
|
|
362880, 3628800, 39916800, 479001600,
|
|
#if SIZEOF_LONG >= 8
|
|
6227020800, 87178291200, 1307674368000,
|
|
20922789888000, 355687428096000, 6402373705728000,
|
|
121645100408832000, 2432902008176640000
|
|
#endif
|
|
};
|
|
|
|
static PyObject *
|
|
math_factorial(PyObject *self, PyObject *arg)
|
|
{
|
|
long x;
|
|
PyObject *result, *odd_part, *two_valuation;
|
|
|
|
if (PyFloat_Check(arg)) {
|
|
PyObject *lx;
|
|
double dx = PyFloat_AS_DOUBLE((PyFloatObject *)arg);
|
|
if (!(Py_IS_FINITE(dx) && dx == floor(dx))) {
|
|
PyErr_SetString(PyExc_ValueError,
|
|
"factorial() only accepts integral values");
|
|
return NULL;
|
|
}
|
|
lx = PyLong_FromDouble(dx);
|
|
if (lx == NULL)
|
|
return NULL;
|
|
x = PyLong_AsLong(lx);
|
|
Py_DECREF(lx);
|
|
}
|
|
else
|
|
x = PyLong_AsLong(arg);
|
|
|
|
if (x == -1 && PyErr_Occurred())
|
|
return NULL;
|
|
if (x < 0) {
|
|
PyErr_SetString(PyExc_ValueError,
|
|
"factorial() not defined for negative values");
|
|
return NULL;
|
|
}
|
|
|
|
/* use lookup table if x is small */
|
|
if (x < (long)(sizeof(SmallFactorials)/sizeof(SmallFactorials[0])))
|
|
return PyLong_FromUnsignedLong(SmallFactorials[x]);
|
|
|
|
/* else express in the form odd_part * 2**two_valuation, and compute as
|
|
odd_part << two_valuation. */
|
|
odd_part = factorial_odd_part(x);
|
|
if (odd_part == NULL)
|
|
return NULL;
|
|
two_valuation = PyLong_FromLong(x - count_set_bits(x));
|
|
if (two_valuation == NULL) {
|
|
Py_DECREF(odd_part);
|
|
return NULL;
|
|
}
|
|
result = PyNumber_Lshift(odd_part, two_valuation);
|
|
Py_DECREF(two_valuation);
|
|
Py_DECREF(odd_part);
|
|
return result;
|
|
}
|
|
|
|
PyDoc_STRVAR(math_factorial_doc,
|
|
"factorial(x) -> Integral\n"
|
|
"\n"
|
|
"Find x!. Raise a ValueError if x is negative or non-integral.");
|
|
|
|
static PyObject *
|
|
math_trunc(PyObject *self, PyObject *number)
|
|
{
|
|
static PyObject *trunc_str = NULL;
|
|
PyObject *trunc, *result;
|
|
|
|
if (Py_TYPE(number)->tp_dict == NULL) {
|
|
if (PyType_Ready(Py_TYPE(number)) < 0)
|
|
return NULL;
|
|
}
|
|
|
|
trunc = _PyObject_LookupSpecial(number, "__trunc__", &trunc_str);
|
|
if (trunc == NULL) {
|
|
if (!PyErr_Occurred())
|
|
PyErr_Format(PyExc_TypeError,
|
|
"type %.100s doesn't define __trunc__ method",
|
|
Py_TYPE(number)->tp_name);
|
|
return NULL;
|
|
}
|
|
result = PyObject_CallFunctionObjArgs(trunc, NULL);
|
|
Py_DECREF(trunc);
|
|
return result;
|
|
}
|
|
|
|
PyDoc_STRVAR(math_trunc_doc,
|
|
"trunc(x:Real) -> Integral\n"
|
|
"\n"
|
|
"Truncates x to the nearest Integral toward 0. Uses the __trunc__ magic method.");
|
|
|
|
static PyObject *
|
|
math_frexp(PyObject *self, PyObject *arg)
|
|
{
|
|
int i;
|
|
double x = PyFloat_AsDouble(arg);
|
|
if (x == -1.0 && PyErr_Occurred())
|
|
return NULL;
|
|
/* deal with special cases directly, to sidestep platform
|
|
differences */
|
|
if (Py_IS_NAN(x) || Py_IS_INFINITY(x) || !x) {
|
|
i = 0;
|
|
}
|
|
else {
|
|
PyFPE_START_PROTECT("in math_frexp", return 0);
|
|
x = frexp(x, &i);
|
|
PyFPE_END_PROTECT(x);
|
|
}
|
|
return Py_BuildValue("(di)", x, i);
|
|
}
|
|
|
|
PyDoc_STRVAR(math_frexp_doc,
|
|
"frexp(x)\n"
|
|
"\n"
|
|
"Return the mantissa and exponent of x, as pair (m, e).\n"
|
|
"m is a float and e is an int, such that x = m * 2.**e.\n"
|
|
"If x is 0, m and e are both 0. Else 0.5 <= abs(m) < 1.0.");
|
|
|
|
static PyObject *
|
|
math_ldexp(PyObject *self, PyObject *args)
|
|
{
|
|
double x, r;
|
|
PyObject *oexp;
|
|
long exp;
|
|
int overflow;
|
|
if (! PyArg_ParseTuple(args, "dO:ldexp", &x, &oexp))
|
|
return NULL;
|
|
|
|
if (PyLong_Check(oexp)) {
|
|
/* on overflow, replace exponent with either LONG_MAX
|
|
or LONG_MIN, depending on the sign. */
|
|
exp = PyLong_AsLongAndOverflow(oexp, &overflow);
|
|
if (exp == -1 && PyErr_Occurred())
|
|
return NULL;
|
|
if (overflow)
|
|
exp = overflow < 0 ? LONG_MIN : LONG_MAX;
|
|
}
|
|
else {
|
|
PyErr_SetString(PyExc_TypeError,
|
|
"Expected an int or long as second argument "
|
|
"to ldexp.");
|
|
return NULL;
|
|
}
|
|
|
|
if (x == 0. || !Py_IS_FINITE(x)) {
|
|
/* NaNs, zeros and infinities are returned unchanged */
|
|
r = x;
|
|
errno = 0;
|
|
} else if (exp > INT_MAX) {
|
|
/* overflow */
|
|
r = copysign(Py_HUGE_VAL, x);
|
|
errno = ERANGE;
|
|
} else if (exp < INT_MIN) {
|
|
/* underflow to +-0 */
|
|
r = copysign(0., x);
|
|
errno = 0;
|
|
} else {
|
|
errno = 0;
|
|
PyFPE_START_PROTECT("in math_ldexp", return 0);
|
|
r = ldexp(x, (int)exp);
|
|
PyFPE_END_PROTECT(r);
|
|
if (Py_IS_INFINITY(r))
|
|
errno = ERANGE;
|
|
}
|
|
|
|
if (errno && is_error(r))
|
|
return NULL;
|
|
return PyFloat_FromDouble(r);
|
|
}
|
|
|
|
PyDoc_STRVAR(math_ldexp_doc,
|
|
"ldexp(x, i)\n\n\
|
|
Return x * (2**i).");
|
|
|
|
static PyObject *
|
|
math_modf(PyObject *self, PyObject *arg)
|
|
{
|
|
double y, x = PyFloat_AsDouble(arg);
|
|
if (x == -1.0 && PyErr_Occurred())
|
|
return NULL;
|
|
/* some platforms don't do the right thing for NaNs and
|
|
infinities, so we take care of special cases directly. */
|
|
if (!Py_IS_FINITE(x)) {
|
|
if (Py_IS_INFINITY(x))
|
|
return Py_BuildValue("(dd)", copysign(0., x), x);
|
|
else if (Py_IS_NAN(x))
|
|
return Py_BuildValue("(dd)", x, x);
|
|
}
|
|
|
|
errno = 0;
|
|
PyFPE_START_PROTECT("in math_modf", return 0);
|
|
x = modf(x, &y);
|
|
PyFPE_END_PROTECT(x);
|
|
return Py_BuildValue("(dd)", x, y);
|
|
}
|
|
|
|
PyDoc_STRVAR(math_modf_doc,
|
|
"modf(x)\n"
|
|
"\n"
|
|
"Return the fractional and integer parts of x. Both results carry the sign\n"
|
|
"of x and are floats.");
|
|
|
|
/* A decent logarithm is easy to compute even for huge longs, but libm can't
|
|
do that by itself -- loghelper can. func is log or log10, and name is
|
|
"log" or "log10". Note that overflow of the result isn't possible: a long
|
|
can contain no more than INT_MAX * SHIFT bits, so has value certainly less
|
|
than 2**(2**64 * 2**16) == 2**2**80, and log2 of that is 2**80, which is
|
|
small enough to fit in an IEEE single. log and log10 are even smaller.
|
|
However, intermediate overflow is possible for a long if the number of bits
|
|
in that long is larger than PY_SSIZE_T_MAX. */
|
|
|
|
static PyObject*
|
|
loghelper(PyObject* arg, double (*func)(double), char *funcname)
|
|
{
|
|
/* If it is long, do it ourselves. */
|
|
if (PyLong_Check(arg)) {
|
|
double x, result;
|
|
Py_ssize_t e;
|
|
|
|
/* Negative or zero inputs give a ValueError. */
|
|
if (Py_SIZE(arg) <= 0) {
|
|
PyErr_SetString(PyExc_ValueError,
|
|
"math domain error");
|
|
return NULL;
|
|
}
|
|
|
|
x = PyLong_AsDouble(arg);
|
|
if (x == -1.0 && PyErr_Occurred()) {
|
|
if (!PyErr_ExceptionMatches(PyExc_OverflowError))
|
|
return NULL;
|
|
/* Here the conversion to double overflowed, but it's possible
|
|
to compute the log anyway. Clear the exception and continue. */
|
|
PyErr_Clear();
|
|
x = _PyLong_Frexp((PyLongObject *)arg, &e);
|
|
if (x == -1.0 && PyErr_Occurred())
|
|
return NULL;
|
|
/* Value is ~= x * 2**e, so the log ~= log(x) + log(2) * e. */
|
|
result = func(x) + func(2.0) * e;
|
|
}
|
|
else
|
|
/* Successfully converted x to a double. */
|
|
result = func(x);
|
|
return PyFloat_FromDouble(result);
|
|
}
|
|
|
|
/* Else let libm handle it by itself. */
|
|
return math_1(arg, func, 0);
|
|
}
|
|
|
|
static PyObject *
|
|
math_log(PyObject *self, PyObject *args)
|
|
{
|
|
PyObject *arg;
|
|
PyObject *base = NULL;
|
|
PyObject *num, *den;
|
|
PyObject *ans;
|
|
|
|
if (!PyArg_UnpackTuple(args, "log", 1, 2, &arg, &base))
|
|
return NULL;
|
|
|
|
num = loghelper(arg, m_log, "log");
|
|
if (num == NULL || base == NULL)
|
|
return num;
|
|
|
|
den = loghelper(base, m_log, "log");
|
|
if (den == NULL) {
|
|
Py_DECREF(num);
|
|
return NULL;
|
|
}
|
|
|
|
ans = PyNumber_TrueDivide(num, den);
|
|
Py_DECREF(num);
|
|
Py_DECREF(den);
|
|
return ans;
|
|
}
|
|
|
|
PyDoc_STRVAR(math_log_doc,
|
|
"log(x[, base])\n\n\
|
|
Return the logarithm of x to the given base.\n\
|
|
If the base not specified, returns the natural logarithm (base e) of x.");
|
|
|
|
static PyObject *
|
|
math_log2(PyObject *self, PyObject *arg)
|
|
{
|
|
return loghelper(arg, m_log2, "log2");
|
|
}
|
|
|
|
PyDoc_STRVAR(math_log2_doc,
|
|
"log2(x)\n\nReturn the base 2 logarithm of x.");
|
|
|
|
static PyObject *
|
|
math_log10(PyObject *self, PyObject *arg)
|
|
{
|
|
return loghelper(arg, m_log10, "log10");
|
|
}
|
|
|
|
PyDoc_STRVAR(math_log10_doc,
|
|
"log10(x)\n\nReturn the base 10 logarithm of x.");
|
|
|
|
static PyObject *
|
|
math_fmod(PyObject *self, PyObject *args)
|
|
{
|
|
PyObject *ox, *oy;
|
|
double r, x, y;
|
|
if (! PyArg_UnpackTuple(args, "fmod", 2, 2, &ox, &oy))
|
|
return NULL;
|
|
x = PyFloat_AsDouble(ox);
|
|
y = PyFloat_AsDouble(oy);
|
|
if ((x == -1.0 || y == -1.0) && PyErr_Occurred())
|
|
return NULL;
|
|
/* fmod(x, +/-Inf) returns x for finite x. */
|
|
if (Py_IS_INFINITY(y) && Py_IS_FINITE(x))
|
|
return PyFloat_FromDouble(x);
|
|
errno = 0;
|
|
PyFPE_START_PROTECT("in math_fmod", return 0);
|
|
r = fmod(x, y);
|
|
PyFPE_END_PROTECT(r);
|
|
if (Py_IS_NAN(r)) {
|
|
if (!Py_IS_NAN(x) && !Py_IS_NAN(y))
|
|
errno = EDOM;
|
|
else
|
|
errno = 0;
|
|
}
|
|
if (errno && is_error(r))
|
|
return NULL;
|
|
else
|
|
return PyFloat_FromDouble(r);
|
|
}
|
|
|
|
PyDoc_STRVAR(math_fmod_doc,
|
|
"fmod(x, y)\n\nReturn fmod(x, y), according to platform C."
|
|
" x % y may differ.");
|
|
|
|
static PyObject *
|
|
math_hypot(PyObject *self, PyObject *args)
|
|
{
|
|
PyObject *ox, *oy;
|
|
double r, x, y;
|
|
if (! PyArg_UnpackTuple(args, "hypot", 2, 2, &ox, &oy))
|
|
return NULL;
|
|
x = PyFloat_AsDouble(ox);
|
|
y = PyFloat_AsDouble(oy);
|
|
if ((x == -1.0 || y == -1.0) && PyErr_Occurred())
|
|
return NULL;
|
|
/* hypot(x, +/-Inf) returns Inf, even if x is a NaN. */
|
|
if (Py_IS_INFINITY(x))
|
|
return PyFloat_FromDouble(fabs(x));
|
|
if (Py_IS_INFINITY(y))
|
|
return PyFloat_FromDouble(fabs(y));
|
|
errno = 0;
|
|
PyFPE_START_PROTECT("in math_hypot", return 0);
|
|
r = hypot(x, y);
|
|
PyFPE_END_PROTECT(r);
|
|
if (Py_IS_NAN(r)) {
|
|
if (!Py_IS_NAN(x) && !Py_IS_NAN(y))
|
|
errno = EDOM;
|
|
else
|
|
errno = 0;
|
|
}
|
|
else if (Py_IS_INFINITY(r)) {
|
|
if (Py_IS_FINITE(x) && Py_IS_FINITE(y))
|
|
errno = ERANGE;
|
|
else
|
|
errno = 0;
|
|
}
|
|
if (errno && is_error(r))
|
|
return NULL;
|
|
else
|
|
return PyFloat_FromDouble(r);
|
|
}
|
|
|
|
PyDoc_STRVAR(math_hypot_doc,
|
|
"hypot(x, y)\n\nReturn the Euclidean distance, sqrt(x*x + y*y).");
|
|
|
|
/* pow can't use math_2, but needs its own wrapper: the problem is
|
|
that an infinite result can arise either as a result of overflow
|
|
(in which case OverflowError should be raised) or as a result of
|
|
e.g. 0.**-5. (for which ValueError needs to be raised.)
|
|
*/
|
|
|
|
static PyObject *
|
|
math_pow(PyObject *self, PyObject *args)
|
|
{
|
|
PyObject *ox, *oy;
|
|
double r, x, y;
|
|
int odd_y;
|
|
|
|
if (! PyArg_UnpackTuple(args, "pow", 2, 2, &ox, &oy))
|
|
return NULL;
|
|
x = PyFloat_AsDouble(ox);
|
|
y = PyFloat_AsDouble(oy);
|
|
if ((x == -1.0 || y == -1.0) && PyErr_Occurred())
|
|
return NULL;
|
|
|
|
/* deal directly with IEEE specials, to cope with problems on various
|
|
platforms whose semantics don't exactly match C99 */
|
|
r = 0.; /* silence compiler warning */
|
|
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.;
|
|
}
|
|
}
|
|
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))
|
|
return NULL;
|
|
else
|
|
return PyFloat_FromDouble(r);
|
|
}
|
|
|
|
PyDoc_STRVAR(math_pow_doc,
|
|
"pow(x, y)\n\nReturn x**y (x to the power of y).");
|
|
|
|
static const double degToRad = Py_MATH_PI / 180.0;
|
|
static const double radToDeg = 180.0 / Py_MATH_PI;
|
|
|
|
static PyObject *
|
|
math_degrees(PyObject *self, PyObject *arg)
|
|
{
|
|
double x = PyFloat_AsDouble(arg);
|
|
if (x == -1.0 && PyErr_Occurred())
|
|
return NULL;
|
|
return PyFloat_FromDouble(x * radToDeg);
|
|
}
|
|
|
|
PyDoc_STRVAR(math_degrees_doc,
|
|
"degrees(x)\n\n\
|
|
Convert angle x from radians to degrees.");
|
|
|
|
static PyObject *
|
|
math_radians(PyObject *self, PyObject *arg)
|
|
{
|
|
double x = PyFloat_AsDouble(arg);
|
|
if (x == -1.0 && PyErr_Occurred())
|
|
return NULL;
|
|
return PyFloat_FromDouble(x * degToRad);
|
|
}
|
|
|
|
PyDoc_STRVAR(math_radians_doc,
|
|
"radians(x)\n\n\
|
|
Convert angle x from degrees to radians.");
|
|
|
|
static PyObject *
|
|
math_isfinite(PyObject *self, PyObject *arg)
|
|
{
|
|
double x = PyFloat_AsDouble(arg);
|
|
if (x == -1.0 && PyErr_Occurred())
|
|
return NULL;
|
|
return PyBool_FromLong((long)Py_IS_FINITE(x));
|
|
}
|
|
|
|
PyDoc_STRVAR(math_isfinite_doc,
|
|
"isfinite(x) -> bool\n\n\
|
|
Return True if x is neither an infinity nor a NaN, and False otherwise.");
|
|
|
|
static PyObject *
|
|
math_isnan(PyObject *self, PyObject *arg)
|
|
{
|
|
double x = PyFloat_AsDouble(arg);
|
|
if (x == -1.0 && PyErr_Occurred())
|
|
return NULL;
|
|
return PyBool_FromLong((long)Py_IS_NAN(x));
|
|
}
|
|
|
|
PyDoc_STRVAR(math_isnan_doc,
|
|
"isnan(x) -> bool\n\n\
|
|
Return True if x is a NaN (not a number), and False otherwise.");
|
|
|
|
static PyObject *
|
|
math_isinf(PyObject *self, PyObject *arg)
|
|
{
|
|
double x = PyFloat_AsDouble(arg);
|
|
if (x == -1.0 && PyErr_Occurred())
|
|
return NULL;
|
|
return PyBool_FromLong((long)Py_IS_INFINITY(x));
|
|
}
|
|
|
|
PyDoc_STRVAR(math_isinf_doc,
|
|
"isinf(x) -> bool\n\n\
|
|
Return True if x is a positive or negative infinity, and False otherwise.");
|
|
|
|
static PyMethodDef math_methods[] = {
|
|
{"acos", math_acos, METH_O, math_acos_doc},
|
|
{"acosh", math_acosh, METH_O, math_acosh_doc},
|
|
{"asin", math_asin, METH_O, math_asin_doc},
|
|
{"asinh", math_asinh, METH_O, math_asinh_doc},
|
|
{"atan", math_atan, METH_O, math_atan_doc},
|
|
{"atan2", math_atan2, METH_VARARGS, math_atan2_doc},
|
|
{"atanh", math_atanh, METH_O, math_atanh_doc},
|
|
{"ceil", math_ceil, METH_O, math_ceil_doc},
|
|
{"copysign", math_copysign, METH_VARARGS, math_copysign_doc},
|
|
{"cos", math_cos, METH_O, math_cos_doc},
|
|
{"cosh", math_cosh, METH_O, math_cosh_doc},
|
|
{"degrees", math_degrees, METH_O, math_degrees_doc},
|
|
{"erf", math_erf, METH_O, math_erf_doc},
|
|
{"erfc", math_erfc, METH_O, math_erfc_doc},
|
|
{"exp", math_exp, METH_O, math_exp_doc},
|
|
{"expm1", math_expm1, METH_O, math_expm1_doc},
|
|
{"fabs", math_fabs, METH_O, math_fabs_doc},
|
|
{"factorial", math_factorial, METH_O, math_factorial_doc},
|
|
{"floor", math_floor, METH_O, math_floor_doc},
|
|
{"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},
|
|
{"isfinite", math_isfinite, METH_O, math_isfinite_doc},
|
|
{"isinf", math_isinf, METH_O, math_isinf_doc},
|
|
{"isnan", math_isnan, METH_O, math_isnan_doc},
|
|
{"ldexp", math_ldexp, METH_VARARGS, math_ldexp_doc},
|
|
{"lgamma", math_lgamma, METH_O, math_lgamma_doc},
|
|
{"log", math_log, METH_VARARGS, math_log_doc},
|
|
{"log1p", math_log1p, METH_O, math_log1p_doc},
|
|
{"log10", math_log10, METH_O, math_log10_doc},
|
|
{"log2", math_log2, METH_O, math_log2_doc},
|
|
{"modf", math_modf, METH_O, math_modf_doc},
|
|
{"pow", math_pow, METH_VARARGS, math_pow_doc},
|
|
{"radians", math_radians, METH_O, math_radians_doc},
|
|
{"sin", math_sin, METH_O, math_sin_doc},
|
|
{"sinh", math_sinh, METH_O, math_sinh_doc},
|
|
{"sqrt", math_sqrt, METH_O, math_sqrt_doc},
|
|
{"tan", math_tan, METH_O, math_tan_doc},
|
|
{"tanh", math_tanh, METH_O, math_tanh_doc},
|
|
{"trunc", math_trunc, METH_O, math_trunc_doc},
|
|
{NULL, NULL} /* sentinel */
|
|
};
|
|
|
|
|
|
PyDoc_STRVAR(module_doc,
|
|
"This module is always available. It provides access to the\n"
|
|
"mathematical functions defined by the C standard.");
|
|
|
|
|
|
static struct PyModuleDef mathmodule = {
|
|
PyModuleDef_HEAD_INIT,
|
|
"math",
|
|
module_doc,
|
|
-1,
|
|
math_methods,
|
|
NULL,
|
|
NULL,
|
|
NULL,
|
|
NULL
|
|
};
|
|
|
|
PyMODINIT_FUNC
|
|
PyInit_math(void)
|
|
{
|
|
PyObject *m;
|
|
|
|
m = PyModule_Create(&mathmodule);
|
|
if (m == NULL)
|
|
goto finally;
|
|
|
|
PyModule_AddObject(m, "pi", PyFloat_FromDouble(Py_MATH_PI));
|
|
PyModule_AddObject(m, "e", PyFloat_FromDouble(Py_MATH_E));
|
|
|
|
finally:
|
|
return m;
|
|
}
|