bpo-26121: Use C library implementation for math functions: (#515)
* bpo-26121: Use C library implementation for math functions: tgamma(), lgamma(), erf() and erfc(). * Don't use tgamma() and lgamma() from libc on OS X.
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@ -133,6 +133,11 @@ Optimizations
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in method calls being faster up to 20%.
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(Contributed by Yury Selivanov and INADA Naoki in :issue:`26110`.)
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* Fast implementation from standard C library is now used for functions
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:func:`~math.tgamma`, :func:`~math.lgamma`, :func:`~math.erf` and
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:func:`~math.erfc` in the :mod:`math` module.
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(Contributed by Serhiy Storchaka in :issue:`26121`.)
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Build and C API Changes
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=======================
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@ -270,6 +270,9 @@ Extension Modules
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Library
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-------
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- bpo-26121: Use C library implementation for math functions:
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tgamma(), lgamma(), erf() and erfc().
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- bpo-29619: os.stat() and os.DirEntry.inode() now convert inode (st_ino) using
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unsigned integers.
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@ -74,6 +74,17 @@ static const double pi = 3.141592653589793238462643383279502884197;
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static const double sqrtpi = 1.772453850905516027298167483341145182798;
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static const double logpi = 1.144729885849400174143427351353058711647;
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#ifndef __APPLE__
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# ifdef HAVE_TGAMMA
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# define USE_TGAMMA
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# endif
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# ifdef HAVE_LGAMMA
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# define USE_LGAMMA
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# endif
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#endif
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#if !defined(USE_TGAMMA) || !defined(USE_LGAMMA)
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static double
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sinpi(double x)
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{
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@ -230,6 +241,7 @@ lanczos_sum(double x)
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}
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return num/den;
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}
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#endif /* !defined(USE_TGAMMA) || !defined(USE_LGAMMA) */
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/* Constant for +infinity, generated in the same way as float('inf'). */
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@ -263,6 +275,14 @@ m_nan(void)
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static double
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m_tgamma(double x)
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{
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#ifdef USE_TGAMMA
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if (x == 0.0) {
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errno = EDOM;
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/* tgamma(+-0.0) = +-inf, divide-by-zero */
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return copysign(Py_HUGE_VAL, x);
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}
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return tgamma(x);
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#else
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double absx, r, y, z, sqrtpow;
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/* special cases */
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@ -354,6 +374,7 @@ m_tgamma(double x)
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if (Py_IS_INFINITY(r))
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errno = ERANGE;
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return r;
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#endif
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}
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/*
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@ -364,7 +385,17 @@ m_tgamma(double x)
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static double
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m_lgamma(double x)
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{
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double r, absx;
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double r;
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#ifdef USE_LGAMMA
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r = lgamma(x);
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if (errno == ERANGE && x == floor(x) && x <= 0.0) {
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errno = EDOM; /* lgamma(n) = inf, divide-by-zero for */
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return Py_HUGE_VAL; /* integers n <= 0 */
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}
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return r;
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#else
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double absx;
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/* special cases */
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if (!Py_IS_FINITE(x)) {
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@ -402,8 +433,11 @@ m_lgamma(double x)
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if (Py_IS_INFINITY(r))
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errno = ERANGE;
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return r;
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#endif
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}
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#if !defined(HAVE_ERF) || !defined(HAVE_ERFC)
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/*
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Implementations of the error function erf(x) and the complementary error
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function erfc(x).
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@ -513,11 +547,16 @@ m_erfc_contfrac(double x)
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return result;
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}
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#endif /* !defined(HAVE_ERF) || !defined(HAVE_ERFC) */
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/* Error function erf(x), for general x */
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static double
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m_erf(double x)
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{
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#ifdef HAVE_ERF
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return erf(x);
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#else
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double absx, cf;
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if (Py_IS_NAN(x))
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@ -529,6 +568,7 @@ m_erf(double x)
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cf = m_erfc_contfrac(absx);
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return x > 0.0 ? 1.0 - cf : cf - 1.0;
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}
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#endif
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}
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/* Complementary error function erfc(x), for general x. */
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@ -536,6 +576,9 @@ m_erf(double x)
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static double
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m_erfc(double x)
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{
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#ifdef HAVE_ERFC
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return erfc(x);
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#else
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double absx, cf;
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if (Py_IS_NAN(x))
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@ -547,6 +590,7 @@ m_erfc(double x)
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cf = m_erfc_contfrac(absx);
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return x > 0.0 ? cf : 2.0 - cf;
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}
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#endif
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}
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/*
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