ReactOS 0.4.15-dev-8349-g6f277e9
tanhf.c
Go to the documentation of this file.
1
2/*******************************************************************************
3MIT License
4-----------
5
6Copyright (c) 2002-2019 Advanced Micro Devices, Inc.
7
8Permission is hereby granted, free of charge, to any person obtaining a copy
9of this Software and associated documentaon files (the "Software"), to deal
10in the Software without restriction, including without limitation the rights
11to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
12copies of the Software, and to permit persons to whom the Software is
13furnished to do so, subject to the following conditions:
14
15The above copyright notice and this permission notice shall be included in
16all copies or substantial portions of the Software.
17
18THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
19IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
20FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
21AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
22LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
23OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
24THE SOFTWARE.
25*******************************************************************************/
26
27#include "libm.h"
28#include "libm_util.h"
29
30#define USE_HANDLE_ERRORF
31#define USE_SPLITEXPF
32#define USE_SCALEFLOAT_2
33#define USE_VALF_WITH_FLAGS
34#include "libm_inlines.h"
35#undef USE_SPLITEXPF
36#undef USE_SCALEFLOAT_2
37#undef USE_VALF_WITH_FLAGS
38#undef USE_HANDLE_ERRORF
39
40#include "libm_errno.h"
41
42#ifdef _MSC_VER
43// Disable "C4163: not available as intrinsic function" warning that older
44// compilers may issue here.
45#pragma warning(disable:4163)
46#pragma function(tanhf)
47#endif
48
49float tanhf(float x)
50{
51 /*
52 The definition of tanh(x) is sinh(x)/cosh(x), which is also equivalent
53 to the following three formulae:
54 1. (exp(x) - exp(-x))/(exp(x) + exp(-x))
55 2. (1 - (2/(exp(2*x) + 1 )))
56 3. (exp(2*x) - 1)/(exp(2*x) + 1)
57 but computationally, some formulae are better on some ranges.
58 */
59 static const float
60 thirtytwo_by_log2 = 4.6166240692e+01F, /* 0x4238aa3b */
61 log2_by_32_lead = 2.1659851074e-02F, /* 0x3cb17000 */
62 log2_by_32_tail = 9.9831822808e-07F, /* 0x3585fdf4 */
63 large_threshold = 10.0F; /* 0x41200000 */
64
65 unsigned int ux, aux;
66 float y, z, p, z1, z2, xneg;
67 int m;
68
69 /* Special cases */
70
71 GET_BITS_SP32(x, ux);
72 aux = ux & ~SIGNBIT_SP32;
73 if (aux < 0x39000000) /* |x| small enough that tanh(x) = x */
74 {
75 if (aux == 0)
76 return x; /* with no inexact */
77 else
78 return valf_with_flags(x, AMD_F_INEXACT);
79 }
80 else if (aux > 0x7f800000) /* |x| is NaN */
81 {
82 unsigned int ufx;
83 GET_BITS_SP32(x, ufx);
84 return _handle_errorf("tanhf", OP_TANH, ufx|0x00400000, _DOMAIN, 0,
85 EDOM, x, 0.0F, 1);
86 }
87// return x + x;
88
89 xneg = 1.0F - 2.0F * (aux != ux);
90
91 y = xneg * x;
92
93 if (y > large_threshold)
94 {
95 /* If x is large then exp(-x) is negligible and
96 formula 1 reduces to plus or minus 1.0 */
97 z = 1.0F;
98 }
99 else if (y <= 1.0F)
100 {
101 float y2;
102 y2 = y*y;
103
104 if (y < 0.9F)
105 {
106 /* Use a [2,1] Remez approximation on [0,0.9]. */
107 z = y + y*y2*
108 (-0.28192806108402678e0F +
109 (-0.14628356048797849e-2F +
110 0.4891631088530669873e-4F*y2)*y2)/
111 (0.845784192581041099e0F +
112 0.3427017942262751343e0F*y2);
113 }
114 else
115 {
116 /* Use a [2,1] Remez approximation on [0.9,1]. */
117 z = y + y*y2*
118 (-0.24069858695196524e0F +
119 (-0.12325644183611929e-2F +
120 0.3827534993599483396e-4F*y2)*y2)/
121 (0.72209738473684982e0F +
122 0.292529068698052819e0F*y2);
123 }
124 }
125 else
126 {
127 /* Compute p = exp(2*y) + 1. The code is basically inlined
128 from exp_amd. */
129
130 splitexpf(2*y, 1.0F, thirtytwo_by_log2, log2_by_32_lead,
131 log2_by_32_tail, &m, &z1, &z2);
132 p = scaleFloat_2(z1 + z2, m) + 1.0F;
133 /* Now reconstruct tanh from p. */
134 z = (1.0F - 2.0F/p);
135 }
136
137 return xneg * z;
138}
float __cdecl _handle_errorf(char *fname, int opcode, unsigned long long value, int type, int flags, int error, float arg1, float arg2, int nargs)
Definition: _handle_error.c:56
#define EDOM
Definition: errno.h:39
GLint GLint GLint GLint GLint x
Definition: gl.h:1548
GLint GLint GLint GLint GLint GLint y
Definition: gl.h:1548
GLfloat GLfloat p
Definition: glext.h:8902
GLdouble GLdouble z
Definition: glext.h:5874
const GLfloat * m
Definition: glext.h:10848
#define _DOMAIN
Definition: math.h:39
#define AMD_F_INEXACT
Definition: libm_new.h:82
float tanhf(float x)
Definition: tanhf.c:49
#define GET_BITS_SP32(x, ux)
Definition: libm_util.h:105
static const WCHAR aux[]
_In_ CLIPOBJ _In_ BRUSHOBJ _In_ LONG _In_ LONG _In_ LONG _In_ LONG y2
Definition: winddi.h:3711