1 /* Compute complex base 10 logarithm.
2 Copyright (C) 1997-2018 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4 Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
5
6 The GNU C Library is free software; you can redistribute it and/or
7 modify it under the terms of the GNU Lesser General Public
8 License as published by the Free Software Foundation; either
9 version 2.1 of the License, or (at your option) any later version.
10
11 The GNU C Library is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 Lesser General Public License for more details.
15
16 You should have received a copy of the GNU Lesser General Public
17 License along with the GNU C Library; if not, see
18 <http://www.gnu.org/licenses/>. */
19
20 #include "quadmath-imp.h"
21
22 /* log_10 (2). */
23 #define LOG10_2 0.3010299956639811952137388947244930267682Q
24
25 /* pi * log10 (e). */
26 #define PI_LOG10E 1.364376353841841347485783625431355770210Q
27
28 __complex128
clog10q(__complex128 x)29 clog10q (__complex128 x)
30 {
31 __complex128 result;
32 int rcls = fpclassifyq (__real__ x);
33 int icls = fpclassifyq (__imag__ x);
34
35 if (__glibc_unlikely (rcls == QUADFP_ZERO && icls == QUADFP_ZERO))
36 {
37 /* Real and imaginary part are 0.0. */
38 __imag__ result = signbitq (__real__ x) ? PI_LOG10E : 0;
39 __imag__ result = copysignq (__imag__ result, __imag__ x);
40 /* Yes, the following line raises an exception. */
41 __real__ result = -1 / fabsq (__real__ x);
42 }
43 else if (__glibc_likely (rcls != QUADFP_NAN && icls != QUADFP_NAN))
44 {
45 /* Neither real nor imaginary part is NaN. */
46 __float128 absx = fabsq (__real__ x), absy = fabsq (__imag__ x);
47 int scale = 0;
48
49 if (absx < absy)
50 {
51 __float128 t = absx;
52 absx = absy;
53 absy = t;
54 }
55
56 if (absx > FLT128_MAX / 2)
57 {
58 scale = -1;
59 absx = scalbnq (absx, scale);
60 absy = (absy >= FLT128_MIN * 2 ? scalbnq (absy, scale) : 0);
61 }
62 else if (absx < FLT128_MIN && absy < FLT128_MIN)
63 {
64 scale = FLT128_MANT_DIG;
65 absx = scalbnq (absx, scale);
66 absy = scalbnq (absy, scale);
67 }
68
69 if (absx == 1 && scale == 0)
70 {
71 __real__ result = (log1pq (absy * absy)
72 * ((__float128) M_LOG10Eq / 2));
73 math_check_force_underflow_nonneg (__real__ result);
74 }
75 else if (absx > 1 && absx < 2 && absy < 1 && scale == 0)
76 {
77 __float128 d2m1 = (absx - 1) * (absx + 1);
78 if (absy >= FLT128_EPSILON)
79 d2m1 += absy * absy;
80 __real__ result = log1pq (d2m1) * ((__float128) M_LOG10Eq / 2);
81 }
82 else if (absx < 1
83 && absx >= 0.5Q
84 && absy < FLT128_EPSILON / 2
85 && scale == 0)
86 {
87 __float128 d2m1 = (absx - 1) * (absx + 1);
88 __real__ result = log1pq (d2m1) * ((__float128) M_LOG10Eq / 2);
89 }
90 else if (absx < 1
91 && absx >= 0.5Q
92 && scale == 0
93 && absx * absx + absy * absy >= 0.5Q)
94 {
95 __float128 d2m1 = __quadmath_x2y2m1q (absx, absy);
96 __real__ result = log1pq (d2m1) * ((__float128) M_LOG10Eq / 2);
97 }
98 else
99 {
100 __float128 d = hypotq (absx, absy);
101 __real__ result = log10q (d) - scale * LOG10_2;
102 }
103
104 __imag__ result = M_LOG10Eq * atan2q (__imag__ x, __real__ x);
105 }
106 else
107 {
108 __imag__ result = nanq ("");
109 if (rcls == QUADFP_INFINITE || icls == QUADFP_INFINITE)
110 /* Real or imaginary part is infinite. */
111 __real__ result = HUGE_VALQ;
112 else
113 __real__ result = nanq ("");
114 }
115
116 return result;
117 }
118