annotate lib/atanl.c @ 17476:6057744acd2c default tip master

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author Karl Berry <karl@freefriends.org>
date Fri, 16 Aug 2013 06:32:22 -0700 (2013-08-16)
parents 2074f2bf7216
children
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
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1 /* Copyright 2001 by Stephen L. Moshier <moshier@na-net.ornl.gov>
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2
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3 This program is free software: you can redistribute it and/or modify
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4 it under the terms of the GNU General Public License as published by
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5 the Free Software Foundation; either version 3 of the License, or
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6 (at your option) any later version.
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7
c115624bf99a New module 'math'. <math.h> replaces mathl.h.
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8 This program is distributed in the hope that it will be useful,
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9 but WITHOUT ANY WARRANTY; without even the implied warranty of
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10 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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11 GNU General Public License for more details.
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12
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13 You should have received a copy of the GNU General Public License
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14 along with this program. If not, see <http://www.gnu.org/licenses/>. */
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15
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16 #include <config.h>
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17
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18 /* Specification. */
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19 #include <math.h>
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20
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21 #if HAVE_SAME_LONG_DOUBLE_AS_DOUBLE
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22
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23 long double
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24 atanl (long double x)
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25 {
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26 return atan (x);
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27 }
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28
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29 #else
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30
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31 /* Code based on glibc/sysdeps/ieee754/ldbl-128/s_atanl.c. */
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32
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33 /* s_atanl.c
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34 *
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35 * Inverse circular tangent for 128-bit long double precision
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36 * (arctangent)
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37 *
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38 *
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39 *
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40 * SYNOPSIS:
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41 *
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42 * long double x, y, atanl();
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43 *
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44 * y = atanl( x );
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45 *
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46 *
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47 *
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48 * DESCRIPTION:
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49 *
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50 * Returns radian angle between -pi/2 and +pi/2 whose tangent is x.
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51 *
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52 * The function uses a rational approximation of the form
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53 * t + t^3 P(t^2)/Q(t^2), optimized for |t| < 0.09375.
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54 *
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55 * The argument is reduced using the identity
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56 * arctan x - arctan u = arctan ((x-u)/(1 + ux))
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57 * and an 83-entry lookup table for arctan u, with u = 0, 1/8, ..., 10.25.
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58 * Use of the table improves the execution speed of the routine.
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59 *
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60 *
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61 *
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62 * ACCURACY:
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63 *
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64 * Relative error:
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65 * arithmetic domain # trials peak rms
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66 * IEEE -19, 19 4e5 1.7e-34 5.4e-35
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67 *
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68 *
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69 * WARNING:
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70 *
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71 * This program uses integer operations on bit fields of floating-point
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72 * numbers. It does not work with data structures other than the
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73 * structure assumed.
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74 *
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75 */
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76
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77 /* arctan(k/8), k = 0, ..., 82 */
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78 static const long double atantbl[84] = {
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79 0.0000000000000000000000000000000000000000E0L,
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80 1.2435499454676143503135484916387102557317E-1L, /* arctan(0.125) */
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81 2.4497866312686415417208248121127581091414E-1L,
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82 3.5877067027057222039592006392646049977698E-1L,
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83 4.6364760900080611621425623146121440202854E-1L,
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84 5.5859931534356243597150821640166127034645E-1L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
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85 6.4350110879328438680280922871732263804151E-1L,
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86 7.1882999962162450541701415152590465395142E-1L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
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87 7.8539816339744830961566084581987572104929E-1L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
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88 8.4415398611317100251784414827164750652594E-1L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
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89 8.9605538457134395617480071802993782702458E-1L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
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90 9.4200004037946366473793717053459358607166E-1L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
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91 9.8279372324732906798571061101466601449688E-1L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
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92 1.0191413442663497346383429170230636487744E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
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93 1.0516502125483736674598673120862998296302E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
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94 1.0808390005411683108871567292171998202703E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
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95 1.1071487177940905030170654601785370400700E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
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96 1.1309537439791604464709335155363278047493E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
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97 1.1525719972156675180401498626127513797495E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
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98 1.1722738811284763866005949441337046149712E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
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99 1.1902899496825317329277337748293183376012E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
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100 1.2068173702852525303955115800565576303133E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
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101 1.2220253232109896370417417439225704908830E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
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102 1.2360594894780819419094519711090786987027E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
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103 1.2490457723982544258299170772810901230778E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
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104 1.2610933822524404193139408812473357720101E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
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105 1.2722973952087173412961937498224804940684E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
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106 1.2827408797442707473628852511364955306249E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
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107 1.2924966677897852679030914214070816845853E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
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108 1.3016288340091961438047858503666855921414E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
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109 1.3101939350475556342564376891719053122733E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
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110 1.3182420510168370498593302023271362531155E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
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111 1.3258176636680324650592392104284756311844E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
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112 1.3329603993374458675538498697331558093700E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
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113 1.3397056595989995393283037525895557411039E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
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114 1.3460851583802539310489409282517796256512E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
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115 1.3521273809209546571891479413898128509842E0L,
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116 1.3578579772154994751124898859640585287459E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
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117 1.3633001003596939542892985278250991189943E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
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118 1.3684746984165928776366381936948529556191E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
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119 1.3734007669450158608612719264449611486510E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
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diff changeset
120 1.3780955681325110444536609641291551522494E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
121 1.3825748214901258580599674177685685125566E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
122 1.3868528702577214543289381097042486034883E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
123 1.3909428270024183486427686943836432060856E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
124 1.3948567013423687823948122092044222644895E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
125 1.3986055122719575950126700816114282335732E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
126 1.4021993871854670105330304794336492676944E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
127 1.4056476493802697809521934019958079881002E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
128 1.4089588955564736949699075250792569287156E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
129 1.4121410646084952153676136718584891599630E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
130 1.4152014988178669079462550975833894394929E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
131 1.4181469983996314594038603039700989523716E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
132 1.4209838702219992566633046424614466661176E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
133 1.4237179714064941189018190466107297503086E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
134 1.4263547484202526397918060597281265695725E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
135 1.4288992721907326964184700745371983590908E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
136 1.4313562697035588982240194668401779312122E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
137 1.4337301524847089866404719096698873648610E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
138 1.4360250423171655234964275337155008780675E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
139 1.4382447944982225979614042479354815855386E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
140 1.4403930189057632173997301031392126865694E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
141 1.4424730991091018200252920599377292525125E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
142 1.4444882097316563655148453598508037025938E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
143 1.4464413322481351841999668424758804165254E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
144 1.4483352693775551917970437843145232637695E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
145 1.4501726582147939000905940595923466567576E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
146 1.4519559822271314199339700039142990228105E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
147 1.4536875822280323362423034480994649820285E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
148 1.4553696664279718992423082296859928222270E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
149 1.4570043196511885530074841089245667532358E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
150 1.4585935117976422128825857356750737658039E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
151 1.4601391056210009726721818194296893361233E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
152 1.4616428638860188872060496086383008594310E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
153 1.4631064559620759326975975316301202111560E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
154 1.4645314639038178118428450961503371619177E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
155 1.4659193880646627234129855241049975398470E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
156 1.4672716522843522691530527207287398276197E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
157 1.4685896086876430842559640450619880951144E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
158 1.4698745421276027686510391411132998919794E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
159 1.4711276743037345918528755717617308518553E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
160 1.4723501675822635384916444186631899205983E0L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
161 1.4735431285433308455179928682541563973416E0L, /* arctan(10.25) */
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
162 1.5707963267948966192313216916397514420986E0L /* pi/2 */
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
163 };
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
164
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
165
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
166 /* arctan t = t + t^3 p(t^2) / q(t^2)
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
167 |t| <= 0.09375
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
168 peak relative error 5.3e-37 */
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
169
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
170 static const long double
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
171 p0 = -4.283708356338736809269381409828726405572E1L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
172 p1 = -8.636132499244548540964557273544599863825E1L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
173 p2 = -5.713554848244551350855604111031839613216E1L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
174 p3 = -1.371405711877433266573835355036413750118E1L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
175 p4 = -8.638214309119210906997318946650189640184E-1L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
176 q0 = 1.285112506901621042780814422948906537959E2L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
177 q1 = 3.361907253914337187957855834229672347089E2L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
178 q2 = 3.180448303864130128268191635189365331680E2L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
179 q3 = 1.307244136980865800160844625025280344686E2L,
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
180 q4 = 2.173623741810414221251136181221172551416E1L;
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
181 /* q5 = 1.000000000000000000000000000000000000000E0 */
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
182
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
183
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
184 long double
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
185 atanl (long double x)
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
186 {
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
187 int k, sign;
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
188 long double t, u, p, q;
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
189
8563
c3d334708928 Better support of signalling NaNs.
Bruno Haible <bruno@clisp.org>
parents: 8186
diff changeset
190 /* Check for zero or NaN. */
c3d334708928 Better support of signalling NaNs.
Bruno Haible <bruno@clisp.org>
parents: 8186
diff changeset
191 if (isnanl (x) || x == 0.0)
c3d334708928 Better support of signalling NaNs.
Bruno Haible <bruno@clisp.org>
parents: 8186
diff changeset
192 return x + x;
4239
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
193
8563
c3d334708928 Better support of signalling NaNs.
Bruno Haible <bruno@clisp.org>
parents: 8186
diff changeset
194 sign = x < 0.0;
4239
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
195
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
196 if (x + x == x)
5327
31a3d72751e2 Add GPL notice, to match glibc's added LGPL notice.
Paul Eggert <eggert@cs.ucla.edu>
parents: 4239
diff changeset
197 {
31a3d72751e2 Add GPL notice, to match glibc's added LGPL notice.
Paul Eggert <eggert@cs.ucla.edu>
parents: 4239
diff changeset
198 /* Infinity. */
31a3d72751e2 Add GPL notice, to match glibc's added LGPL notice.
Paul Eggert <eggert@cs.ucla.edu>
parents: 4239
diff changeset
199 if (sign)
12421
e8d2c6fc33ad Use spaces for indentation, not tabs.
Bruno Haible <bruno@clisp.org>
parents: 10667
diff changeset
200 return -atantbl[83];
5327
31a3d72751e2 Add GPL notice, to match glibc's added LGPL notice.
Paul Eggert <eggert@cs.ucla.edu>
parents: 4239
diff changeset
201 else
12421
e8d2c6fc33ad Use spaces for indentation, not tabs.
Bruno Haible <bruno@clisp.org>
parents: 10667
diff changeset
202 return atantbl[83];
5327
31a3d72751e2 Add GPL notice, to match glibc's added LGPL notice.
Paul Eggert <eggert@cs.ucla.edu>
parents: 4239
diff changeset
203 }
4239
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
204
5327
31a3d72751e2 Add GPL notice, to match glibc's added LGPL notice.
Paul Eggert <eggert@cs.ucla.edu>
parents: 4239
diff changeset
205 if (sign)
31a3d72751e2 Add GPL notice, to match glibc's added LGPL notice.
Paul Eggert <eggert@cs.ucla.edu>
parents: 4239
diff changeset
206 x = -x;
4239
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
207
5327
31a3d72751e2 Add GPL notice, to match glibc's added LGPL notice.
Paul Eggert <eggert@cs.ucla.edu>
parents: 4239
diff changeset
208 if (x >= 10.25)
4239
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
209 {
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
210 k = 83;
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
211 t = -1.0/x;
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
212 }
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
213 else
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
214 {
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
215 /* Index of nearest table element.
12421
e8d2c6fc33ad Use spaces for indentation, not tabs.
Bruno Haible <bruno@clisp.org>
parents: 10667
diff changeset
216 Roundoff to integer is asymmetrical to avoid cancellation when t < 0
4239
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
217 (cf. fdlibm). */
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
218 k = 8.0 * x + 0.25;
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
219 u = 0.125 * k;
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
220 /* Small arctan argument. */
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
221 t = (x - u) / (1.0 + x * u);
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
222 }
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
223
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
224 /* Arctan of small argument t. */
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
225 u = t * t;
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
226 p = ((((p4 * u) + p3) * u + p2) * u + p1) * u + p0;
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
227 q = ((((u + q4) * u + q3) * u + q2) * u + q1) * u + q0;
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
228 u = t * u * p / q + t;
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
229
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
230 /* arctan x = arctan u + arctan t */
5327
31a3d72751e2 Add GPL notice, to match glibc's added LGPL notice.
Paul Eggert <eggert@cs.ucla.edu>
parents: 4239
diff changeset
231 u = atantbl[k] + u;
31a3d72751e2 Add GPL notice, to match glibc's added LGPL notice.
Paul Eggert <eggert@cs.ucla.edu>
parents: 4239
diff changeset
232 if (sign)
31a3d72751e2 Add GPL notice, to match glibc's added LGPL notice.
Paul Eggert <eggert@cs.ucla.edu>
parents: 4239
diff changeset
233 return (-u);
31a3d72751e2 Add GPL notice, to match glibc's added LGPL notice.
Paul Eggert <eggert@cs.ucla.edu>
parents: 4239
diff changeset
234 else
31a3d72751e2 Add GPL notice, to match glibc's added LGPL notice.
Paul Eggert <eggert@cs.ucla.edu>
parents: 4239
diff changeset
235 return u;
4239
b33b8603715c Transcendental functions for 'long double', from Paolo Bonzini.
Bruno Haible <bruno@clisp.org>
parents:
diff changeset
236 }
15944
4b3d35486c68 atanl: Simplify for platforms where 'long double' == 'double'.
Bruno Haible <bruno@clisp.org>
parents: 12421
diff changeset
237
4b3d35486c68 atanl: Simplify for platforms where 'long double' == 'double'.
Bruno Haible <bruno@clisp.org>
parents: 12421
diff changeset
238 #endif