projects / thirdparty / glibc.git / blame
| Commit | Line | Data |
|---|---|---|
| 04277e02 | 1 | /* Copyright (C) 2011-2019 Free Software Foundation, Inc. |
| 0ac5ae23 UD |
2 | This file is part of the GNU C Library. |
| 3 | Contributed by Ulrich Drepper <drepper@gmail.com>, 2011. | |
| f7eac6eb | 4 | |
| 0ac5ae23 UD |
5 | The GNU C Library is free software; you can redistribute it and/or |
| 6 | modify it under the terms of the GNU Lesser General Public | |
| 7 | License as published by the Free Software Foundation; either | |
| 8 | version 2.1 of the License, or (at your option) any later version. | |
| 9 | ||
| 10 | The GNU C Library is distributed in the hope that it will be useful, | |
| 11 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
| 12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
| 13 | Lesser General Public License for more details. | |
| 14 | ||
| 15 | You should have received a copy of the GNU Lesser General Public | |
| 59ba27a6 PE |
16 | License along with the GNU C Library; if not, see |
| 17 | <http://www.gnu.org/licenses/>. */ | |
| 0ac5ae23 UD |
18 | |
| 19 | ||
| 20 | /* __ieee754_atanh(x) | |
| 21 | Method : | |
| 22 | 1.Reduced x to positive by atanh(-x) = -atanh(x) | |
| 23 | 2.For x>=0.5 | |
| 24 | 1 2x x | |
| 25 | atanh(x) = --- * log(1 + -------) = 0.5 * log1p(2 * --------) | |
| 26 | 2 1 - x 1 - x | |
| 27 | ||
| 28 | For x<0.5 | |
| 29 | atanh(x) = 0.5*log1p(2x+2x*x/(1-x)) | |
| f7eac6eb | 30 | |
| 0ac5ae23 UD |
31 | Special cases: |
| 32 | atanh(x) is NaN if |x| > 1 with signal; | |
| 33 | atanh(NaN) is that NaN with no signal; | |
| 34 | atanh(+-1) is +-INF with signal. | |
| f7eac6eb | 35 | |
| 0ac5ae23 UD |
36 | */ |
| 37 | ||
| 8020a808 | 38 | #include <float.h> |
| 0ac5ae23 | 39 | #include <inttypes.h> |
| 1ed0291c | 40 | #include <math.h> |
| b4d5b8b0 | 41 | #include <math-barriers.h> |
| 1ed0291c | 42 | #include <math_private.h> |
| 8f5b00d3 | 43 | #include <math-underflow.h> |
| f7eac6eb | 44 | |
| 0ac5ae23 UD |
45 | static const float huge = 1e30; |
| 46 | ||
| 47 | float | |
| 48 | __ieee754_atanhf (float x) | |
| f7eac6eb | 49 | { |
| 0ac5ae23 UD |
50 | float xa = fabsf (x); |
| 51 | float t; | |
| 92221550 | 52 | if (isless (xa, 0.5f)) |
| 0ac5ae23 | 53 | { |
| a1ffb40e | 54 | if (__glibc_unlikely (xa < 0x1.0p-28f)) |
| d7826aa1 UD |
55 | { |
| 56 | math_force_eval (huge + x); | |
| d96164c3 | 57 | math_check_force_underflow (x); |
| d7826aa1 UD |
58 | return x; |
| 59 | } | |
| 0ac5ae23 UD |
60 | |
| 61 | t = xa + xa; | |
| 62 | t = 0.5f * __log1pf (t + t * xa / (1.0f - xa)); | |
| 63 | } | |
| a1ffb40e | 64 | else if (__glibc_likely (isless (xa, 1.0f))) |
| 0ac5ae23 UD |
65 | t = 0.5f * __log1pf ((xa + xa) / (1.0f - xa)); |
| 66 | else | |
| 67 | { | |
| 92221550 | 68 | if (isgreater (xa, 1.0f)) |
| 0ac5ae23 UD |
69 | return (x - x) / (x - x); |
| 70 | ||
| 71 | return x / 0.0f; | |
| 72 | } | |
| 73 | ||
| 81dca813 | 74 | return copysignf (t, x); |
| f7eac6eb | 75 | } |
| 0ac5ae23 | 76 | strong_alias (__ieee754_atanhf, __atanhf_finite) |