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1 /* Compute complex natural logarithm.
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2 Copyright (C) 1997-2018 Free Software Foundation, Inc.
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3 This file is part of the GNU C Library.
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4 Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
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5
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6 The GNU C Library is free software; you can redistribute it and/or
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7 modify it under the terms of the GNU Lesser General Public
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8 License as published by the Free Software Foundation; either
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9 version 2.1 of the License, or (at your option) any later version.
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10
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11 The GNU C Library is distributed in the hope that it will be useful,
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12 but WITHOUT ANY WARRANTY; without even the implied warranty of
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13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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14 Lesser General Public License for more details.
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15
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16 You should have received a copy of the GNU Lesser General Public
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17 License along with the GNU C Library; if not, see
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18 <http://www.gnu.org/licenses/>. */
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19
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20 #include "quadmath-imp.h"
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21
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22 __complex128
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23 clogq (__complex128 x)
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24 {
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25 __complex128 result;
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26 int rcls = fpclassifyq (__real__ x);
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27 int icls = fpclassifyq (__imag__ x);
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28
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29 if (__glibc_unlikely (rcls == QUADFP_ZERO && icls == QUADFP_ZERO))
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30 {
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31 /* Real and imaginary part are 0.0. */
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32 __imag__ result = signbitq (__real__ x) ? (__float128) M_PIq : 0;
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33 __imag__ result = copysignq (__imag__ result, __imag__ x);
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34 /* Yes, the following line raises an exception. */
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35 __real__ result = -1 / fabsq (__real__ x);
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36 }
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37 else if (__glibc_likely (rcls != QUADFP_NAN && icls != QUADFP_NAN))
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38 {
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39 /* Neither real nor imaginary part is NaN. */
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40 __float128 absx = fabsq (__real__ x), absy = fabsq (__imag__ x);
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41 int scale = 0;
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42
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43 if (absx < absy)
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44 {
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45 __float128 t = absx;
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46 absx = absy;
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47 absy = t;
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48 }
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49
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50 if (absx > FLT128_MAX / 2)
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51 {
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52 scale = -1;
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53 absx = scalbnq (absx, scale);
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54 absy = (absy >= FLT128_MIN * 2 ? scalbnq (absy, scale) : 0);
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55 }
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56 else if (absx < FLT128_MIN && absy < FLT128_MIN)
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57 {
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58 scale = FLT128_MANT_DIG;
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59 absx = scalbnq (absx, scale);
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60 absy = scalbnq (absy, scale);
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61 }
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62
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63 if (absx == 1 && scale == 0)
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64 {
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65 __real__ result = log1pq (absy * absy) / 2;
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66 math_check_force_underflow_nonneg (__real__ result);
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67 }
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68 else if (absx > 1 && absx < 2 && absy < 1 && scale == 0)
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69 {
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70 __float128 d2m1 = (absx - 1) * (absx + 1);
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71 if (absy >= FLT128_EPSILON)
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72 d2m1 += absy * absy;
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73 __real__ result = log1pq (d2m1) / 2;
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74 }
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75 else if (absx < 1
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76 && absx >= 0.5Q
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77 && absy < FLT128_EPSILON / 2
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78 && scale == 0)
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79 {
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80 __float128 d2m1 = (absx - 1) * (absx + 1);
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81 __real__ result = log1pq (d2m1) / 2;
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82 }
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83 else if (absx < 1
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84 && absx >= 0.5Q
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85 && scale == 0
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86 && absx * absx + absy * absy >= 0.5Q)
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87 {
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88 __float128 d2m1 = __quadmath_x2y2m1q (absx, absy);
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89 __real__ result = log1pq (d2m1) / 2;
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90 }
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91 else
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92 {
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93 __float128 d = hypotq (absx, absy);
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94 __real__ result = logq (d) - scale * (__float128) M_LN2q;
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95 }
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96
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97 __imag__ result = atan2q (__imag__ x, __real__ x);
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98 }
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99 else
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100 {
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101 __imag__ result = nanq ("");
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102 if (rcls == QUADFP_INFINITE || icls == QUADFP_INFINITE)
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103 /* Real or imaginary part is infinite. */
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104 __real__ result = HUGE_VALQ;
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105 else
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106 __real__ result = nanq ("");
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107 }
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108
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109 return result;
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110 }
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