1 /* Compute complex base 10 logarithm.
2 Copyright (C) 1997-2014 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4 Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
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.
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.
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/>. */
22 #include <math_private.h>
26 #define M_LOG10_2f 0.3010299956639811952137388947244930267682f
29 #define M_PI_LOG10Ef 1.364376353841841347485783625431355770210f
32 __clog10f (__complex__ float x)
34 __complex__ float result;
35 int rcls = fpclassify (__real__ x);
36 int icls = fpclassify (__imag__ x);
38 if (__glibc_unlikely (rcls == FP_ZERO && icls == FP_ZERO))
40 /* Real and imaginary part are 0.0. */
41 __imag__ result = signbit (__real__ x) ? M_PI_LOG10Ef : 0.0;
42 __imag__ result = __copysignf (__imag__ result, __imag__ x);
43 /* Yes, the following line raises an exception. */
44 __real__ result = -1.0 / fabsf (__real__ x);
46 else if (__glibc_likely (rcls != FP_NAN && icls != FP_NAN))
48 /* Neither real nor imaginary part is NaN. */
49 float absx = fabsf (__real__ x), absy = fabsf (__imag__ x);
59 if (absx > FLT_MAX / 2.0f)
62 absx = __scalbnf (absx, scale);
63 absy = (absy >= FLT_MIN * 2.0f ? __scalbnf (absy, scale) : 0.0f);
65 else if (absx < FLT_MIN && absy < FLT_MIN)
68 absx = __scalbnf (absx, scale);
69 absy = __scalbnf (absy, scale);
72 if (absx == 1.0f && scale == 0)
74 float absy2 = absy * absy;
75 if (absy2 <= FLT_MIN * 2.0f * (float) M_LN10)
77 #if __FLT_EVAL_METHOD__ == 0
79 = (absy2 / 2.0f - absy2 * absy2 / 4.0f) * (float) M_LOG10E;
81 volatile float force_underflow = absy2 * absy2 / 4.0f;
83 = (absy2 / 2.0f - force_underflow) * (float) M_LOG10E;
87 __real__ result = __log1pf (absy2) * ((float) M_LOG10E / 2.0f);
89 else if (absx > 1.0f && absx < 2.0f && absy < 1.0f && scale == 0)
91 float d2m1 = (absx - 1.0f) * (absx + 1.0f);
92 if (absy >= FLT_EPSILON)
94 __real__ result = __log1pf (d2m1) * ((float) M_LOG10E / 2.0f);
98 && absy < FLT_EPSILON / 2.0f
101 float d2m1 = (absx - 1.0f) * (absx + 1.0f);
102 __real__ result = __log1pf (d2m1) * ((float) M_LOG10E / 2.0f);
104 else if (absx < 1.0f && (absx >= 0.75f || absy >= 0.5f) && scale == 0)
106 float d2m1 = __x2y2m1f (absx, absy);
107 __real__ result = __log1pf (d2m1) * ((float) M_LOG10E / 2.0f);
111 float d = __ieee754_hypotf (absx, absy);
112 __real__ result = __ieee754_log10f (d) - scale * M_LOG10_2f;
115 __imag__ result = M_LOG10E * __ieee754_atan2f (__imag__ x, __real__ x);
119 __imag__ result = __nanf ("");
120 if (rcls == FP_INFINITE || icls == FP_INFINITE)
121 /* Real or imaginary part is infinite. */
122 __real__ result = HUGE_VALF;
124 __real__ result = __nanf ("");
130 weak_alias (__clog10f, clog10f)