diff options
Diffstat (limited to 'sysdeps/ieee754/ldbl-128ibm/lgamma_productl.c')
-rw-r--r-- | sysdeps/ieee754/ldbl-128ibm/lgamma_productl.c | 38 |
1 files changed, 38 insertions, 0 deletions
diff --git a/sysdeps/ieee754/ldbl-128ibm/lgamma_productl.c b/sysdeps/ieee754/ldbl-128ibm/lgamma_productl.c new file mode 100644 index 0000000000..c5fa81be8e --- /dev/null +++ b/sysdeps/ieee754/ldbl-128ibm/lgamma_productl.c @@ -0,0 +1,38 @@ +/* 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; +} |