1/* s_atanf.c -- float version of s_atan.c.
2 */
3
4/*
5 * ====================================================
6 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
7 *
8 * Developed at SunPro, a Sun Microsystems, Inc. business.
9 * Permission to use, copy, modify, and distribute this
10 * software is freely granted, provided that this notice
11 * is preserved.
12 * ====================================================
13 */
14
15#if defined(LIBM_SCCS) && !defined(lint)
16static char rcsid[] = "$NetBSD: s_atanf.c,v 1.4 1995/05/10 20:46:47 jtc Exp $";
17#endif
18
19#include <float.h>
20#include <math.h>
21#include <math_private.h>
22#include <math-underflow.h>
23#include <libm-alias-float.h>
24
25static const float atanhi[] = {
26 4.6364760399e-01, /* atan(0.5)hi 0x3eed6338 */
27 7.8539812565e-01, /* atan(1.0)hi 0x3f490fda */
28 9.8279368877e-01, /* atan(1.5)hi 0x3f7b985e */
29 1.5707962513e+00, /* atan(inf)hi 0x3fc90fda */
30};
31
32static const float atanlo[] = {
33 5.0121582440e-09, /* atan(0.5)lo 0x31ac3769 */
34 3.7748947079e-08, /* atan(1.0)lo 0x33222168 */
35 3.4473217170e-08, /* atan(1.5)lo 0x33140fb4 */
36 7.5497894159e-08, /* atan(inf)lo 0x33a22168 */
37};
38
39static const float aT[] = {
40 3.3333334327e-01, /* 0x3eaaaaaa */
41 -2.0000000298e-01, /* 0xbe4ccccd */
42 1.4285714924e-01, /* 0x3e124925 */
43 -1.1111110449e-01, /* 0xbde38e38 */
44 9.0908870101e-02, /* 0x3dba2e6e */
45 -7.6918758452e-02, /* 0xbd9d8795 */
46 6.6610731184e-02, /* 0x3d886b35 */
47 -5.8335702866e-02, /* 0xbd6ef16b */
48 4.9768779427e-02, /* 0x3d4bda59 */
49 -3.6531571299e-02, /* 0xbd15a221 */
50 1.6285819933e-02, /* 0x3c8569d7 */
51};
52
53static const float
54one = 1.0,
55huge = 1.0e30;
56
57float __atanf(float x)
58{
59 float w,s1,s2,z;
60 int32_t ix,hx,id;
61
62 GET_FLOAT_WORD(hx,x);
63 ix = hx&0x7fffffff;
64 if(ix>=0x4c000000) { /* if |x| >= 2^25 */
65 if(ix>0x7f800000)
66 return x+x; /* NaN */
67 if(hx>0) return atanhi[3]+atanlo[3];
68 else return -atanhi[3]-atanlo[3];
69 } if (ix < 0x3ee00000) { /* |x| < 0.4375 */
70 if (ix < 0x31000000) { /* |x| < 2^-29 */
71 math_check_force_underflow (x);
72 if(huge+x>one) return x; /* raise inexact */
73 }
74 id = -1;
75 } else {
76 x = fabsf(x);
77 if (ix < 0x3f980000) { /* |x| < 1.1875 */
78 if (ix < 0x3f300000) { /* 7/16 <=|x|<11/16 */
79 id = 0; x = ((float)2.0*x-one)/((float)2.0+x);
80 } else { /* 11/16<=|x|< 19/16 */
81 id = 1; x = (x-one)/(x+one);
82 }
83 } else {
84 if (ix < 0x401c0000) { /* |x| < 2.4375 */
85 id = 2; x = (x-(float)1.5)/(one+(float)1.5*x);
86 } else { /* 2.4375 <= |x| < 2^66 */
87 id = 3; x = -(float)1.0/x;
88 }
89 }}
90 /* end of argument reduction */
91 z = x*x;
92 w = z*z;
93 /* break sum from i=0 to 10 aT[i]z**(i+1) into odd and even poly */
94 s1 = z*(aT[0]+w*(aT[2]+w*(aT[4]+w*(aT[6]+w*(aT[8]+w*aT[10])))));
95 s2 = w*(aT[1]+w*(aT[3]+w*(aT[5]+w*(aT[7]+w*aT[9]))));
96 if (id<0) return x - x*(s1+s2);
97 else {
98 z = atanhi[id] - ((x*(s1+s2) - atanlo[id]) - x);
99 return (hx<0)? -z:z;
100 }
101}
102libm_alias_float (__atan, atan)
103