mirror of
https://sourceware.org/git/glibc.git
synced 2024-12-27 21:20:18 +00:00
39 lines
1.4 KiB
C
39 lines
1.4 KiB
C
/* Compute a product of 1 + (T/X), 1 + (T/(X+1)), ....
|
|
Copyright (C) 2015-2016 Free Software Foundation, Inc.
|
|
This file is part of the GNU C Library.
|
|
|
|
The GNU C Library is free software; you can redistribute it and/or
|
|
modify it under the terms of the GNU Lesser General Public
|
|
License as published by the Free Software Foundation; either
|
|
version 2.1 of the License, or (at your option) any later version.
|
|
|
|
The GNU C Library is distributed in the hope that it will be useful,
|
|
but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
|
|
Lesser General Public License for more details.
|
|
|
|
You should have received a copy of the GNU Lesser General Public
|
|
License along with the GNU C Library; if not, see
|
|
<http://www.gnu.org/licenses/>. */
|
|
|
|
#include <math.h>
|
|
#include <math_private.h>
|
|
#include <float.h>
|
|
|
|
/* Compute the product of 1 + (T / (X + X_EPS)), 1 + (T / (X + X_EPS +
|
|
1)), ..., 1 + (T / (X + X_EPS + N - 1)), minus 1. X is such that
|
|
all the values X + 1, ..., X + N - 1 are exactly representable, and
|
|
X_EPS / X is small enough that factors quadratic in it can be
|
|
neglected. */
|
|
|
|
long double
|
|
__lgamma_productl (long double t, long double x, long double x_eps, int n)
|
|
{
|
|
long double x_full = x + x_eps;
|
|
long double ret = 0;
|
|
for (int i = 0; i < n; i++)
|
|
/* FIXME: no extra precision used. */
|
|
ret += (t / (x_full + i)) * (1 + ret);
|
|
return ret;
|
|
}
|