1 1.1 mrg /* Compute a product of 1 + (T/X), 1 + (T/(X+1)), .... 2 1.1 mrg Copyright (C) 2015-2018 Free Software Foundation, Inc. 3 1.1 mrg This file is part of the GNU C Library. 4 1.1 mrg 5 1.1 mrg The GNU C Library is free software; you can redistribute it and/or 6 1.1 mrg modify it under the terms of the GNU Lesser General Public 7 1.1 mrg License as published by the Free Software Foundation; either 8 1.1 mrg version 2.1 of the License, or (at your option) any later version. 9 1.1 mrg 10 1.1 mrg The GNU C Library is distributed in the hope that it will be useful, 11 1.1 mrg but WITHOUT ANY WARRANTY; without even the implied warranty of 12 1.1 mrg MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 13 1.1 mrg Lesser General Public License for more details. 14 1.1 mrg 15 1.1 mrg You should have received a copy of the GNU Lesser General Public 16 1.1 mrg License along with the GNU C Library; if not, see 17 1.1 mrg <http://www.gnu.org/licenses/>. */ 18 1.1 mrg 19 1.1 mrg #include "quadmath-imp.h" 20 1.1 mrg 21 1.1 mrg /* Compute the product of 1 + (T / (X + X_EPS)), 1 + (T / (X + X_EPS + 22 1.1 mrg 1)), ..., 1 + (T / (X + X_EPS + N - 1)), minus 1. X is such that 23 1.1 mrg all the values X + 1, ..., X + N - 1 are exactly representable, and 24 1.1 mrg X_EPS / X is small enough that factors quadratic in it can be 25 1.1 mrg neglected. */ 26 1.1 mrg 27 1.1 mrg __float128 28 1.1 mrg __quadmath_lgamma_productq (__float128 t, __float128 x, __float128 x_eps, int n) 29 1.1 mrg { 30 1.1 mrg __float128 ret = 0, ret_eps = 0; 31 1.1 mrg for (int i = 0; i < n; i++) 32 1.1 mrg { 33 1.1 mrg __float128 xi = x + i; 34 1.1 mrg __float128 quot = t / xi; 35 1.1 mrg __float128 mhi, mlo; 36 1.1 mrg mul_splitq (&mhi, &mlo, quot, xi); 37 1.1 mrg __float128 quot_lo = (t - mhi - mlo) / xi - t * x_eps / (xi * xi); 38 1.1 mrg /* We want (1 + RET + RET_EPS) * (1 + QUOT + QUOT_LO) - 1. */ 39 1.1 mrg __float128 rhi, rlo; 40 1.1 mrg mul_splitq (&rhi, &rlo, ret, quot); 41 1.1 mrg __float128 rpq = ret + quot; 42 1.1 mrg __float128 rpq_eps = (ret - rpq) + quot; 43 1.1 mrg __float128 nret = rpq + rhi; 44 1.1 mrg __float128 nret_eps = (rpq - nret) + rhi; 45 1.1 mrg ret_eps += (rpq_eps + nret_eps + rlo + ret_eps * quot 46 1.1 mrg + quot_lo + quot_lo * (ret + ret_eps)); 47 1.1 mrg ret = nret; 48 1.1 mrg } 49 1.1 mrg return ret + ret_eps; 50 1.1 mrg } 51
Indexes created Sun Mar 01 05:31:48 UTC 2026