long double
__exp2l (long double x) /* wrapper exp2l */
{
#ifdef _IEEE_LIBM
return __ieee754_exp2l (x);
#else
long double z;
z = __ieee754_exp2l (x);
if (_LIB_VERSION != _IEEE_ && __finitel (x))
{
if (x > o_threshold)
return __kernel_standard (x, x, 244); /* exp2l overflow */
else if (x <= u_threshold)
return __kernel_standard (x, x, 245); /* exp2l underflow */
}
return z;
#endif
}
static long double
gammal_positive (long double x, int *exp2_adj)
{
int local_signgam;
if (x < 0.5L)
{
*exp2_adj = 0;
return __ieee754_expl (__ieee754_lgammal_r (x + 1, &local_signgam)) / x;
}
else if (x <= 1.5L)
{
*exp2_adj = 0;
return __ieee754_expl (__ieee754_lgammal_r (x, &local_signgam));
}
else if (x < 12.5L)
{
/* Adjust into the range for using exp (lgamma). */
*exp2_adj = 0;
long double n = __ceill (x - 1.5L);
long double x_adj = x - n;
long double eps;
long double prod = __gamma_productl (x_adj, 0, n, &eps);
return (__ieee754_expl (__ieee754_lgammal_r (x_adj, &local_signgam))
* prod * (1.0L + eps));
}
else
{
long double eps = 0;
long double x_eps = 0;
long double x_adj = x;
long double prod = 1;
if (x < 24.0L)
{
/* Adjust into the range for applying Stirling's
approximation. */
long double n = __ceill (24.0L - x);
x_adj = x + n;
x_eps = (x - (x_adj - n));
prod = __gamma_productl (x_adj - n, x_eps, n, &eps);
}
/* The result is now gamma (X_ADJ + X_EPS) / (PROD * (1 + EPS)).
Compute gamma (X_ADJ + X_EPS) using Stirling's approximation,
starting by computing pow (X_ADJ, X_ADJ) with a power of 2
factored out. */
long double exp_adj = -eps;
long double x_adj_int = __roundl (x_adj);
long double x_adj_frac = x_adj - x_adj_int;
int x_adj_log2;
long double x_adj_mant = __frexpl (x_adj, &x_adj_log2);
if (x_adj_mant < M_SQRT1_2l)
{
x_adj_log2--;
x_adj_mant *= 2.0L;
}
*exp2_adj = x_adj_log2 * (int) x_adj_int;
long double ret = (__ieee754_powl (x_adj_mant, x_adj)
* __ieee754_exp2l (x_adj_log2 * x_adj_frac)
* __ieee754_expl (-x_adj)
* __ieee754_sqrtl (2 * M_PIl / x_adj)
/ prod);
exp_adj += x_eps * __ieee754_logl (x_adj);
long double bsum = gamma_coeff[NCOEFF - 1];
long double x_adj2 = x_adj * x_adj;
for (size_t i = 1; i <= NCOEFF - 1; i++)
bsum = bsum / x_adj2 + gamma_coeff[NCOEFF - 1 - i];
exp_adj += bsum / x_adj;
return ret + ret * __expm1l (exp_adj);
}
}
