Rev 4872 | Details | Compare with Previous | Last modification | View Log | RSS feed
| Rev | Author | Line No. | Line |
|---|---|---|---|
| 4349 | Serge | 1 | /* sf_atan.c -- float version of s_atan.c. |
| 2 | * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com. |
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| 3 | */ |
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| 4 | |||
| 5 | /* |
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| 6 | * ==================================================== |
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| 7 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
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| 8 | * |
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| 9 | * Developed at SunPro, a Sun Microsystems, Inc. business. |
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| 10 | * Permission to use, copy, modify, and distribute this |
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| 11 | * software is freely granted, provided that this notice |
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| 12 | * is preserved. |
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| 13 | * ==================================================== |
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| 14 | * |
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| 15 | */ |
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| 16 | |||
| 17 | #include "fdlibm.h" |
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| 18 | |||
| 19 | #ifdef __STDC__ |
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| 20 | static const float atanhi[] = { |
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| 21 | #else |
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| 22 | static float atanhi[] = { |
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| 23 | #endif |
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| 24 | 4.6364760399e-01, /* atan(0.5)hi 0x3eed6338 */ |
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| 25 | 7.8539812565e-01, /* atan(1.0)hi 0x3f490fda */ |
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| 26 | 9.8279368877e-01, /* atan(1.5)hi 0x3f7b985e */ |
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| 27 | 1.5707962513e+00, /* atan(inf)hi 0x3fc90fda */ |
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| 28 | }; |
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| 29 | |||
| 30 | #ifdef __STDC__ |
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| 31 | static const float atanlo[] = { |
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| 32 | #else |
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| 33 | static float atanlo[] = { |
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| 34 | #endif |
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| 35 | 5.0121582440e-09, /* atan(0.5)lo 0x31ac3769 */ |
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| 36 | 3.7748947079e-08, /* atan(1.0)lo 0x33222168 */ |
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| 37 | 3.4473217170e-08, /* atan(1.5)lo 0x33140fb4 */ |
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| 38 | 7.5497894159e-08, /* atan(inf)lo 0x33a22168 */ |
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| 39 | }; |
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| 40 | |||
| 41 | #ifdef __STDC__ |
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| 42 | static const float aT[] = { |
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| 43 | #else |
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| 44 | static float aT[] = { |
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| 45 | #endif |
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| 46 | 3.3333334327e-01, /* 0x3eaaaaaa */ |
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| 47 | -2.0000000298e-01, /* 0xbe4ccccd */ |
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| 48 | 1.4285714924e-01, /* 0x3e124925 */ |
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| 49 | -1.1111110449e-01, /* 0xbde38e38 */ |
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| 50 | 9.0908870101e-02, /* 0x3dba2e6e */ |
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| 51 | -7.6918758452e-02, /* 0xbd9d8795 */ |
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| 52 | 6.6610731184e-02, /* 0x3d886b35 */ |
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| 53 | -5.8335702866e-02, /* 0xbd6ef16b */ |
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| 54 | 4.9768779427e-02, /* 0x3d4bda59 */ |
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| 55 | -3.6531571299e-02, /* 0xbd15a221 */ |
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| 56 | 1.6285819933e-02, /* 0x3c8569d7 */ |
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| 57 | }; |
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| 58 | |||
| 59 | #ifdef __STDC__ |
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| 60 | static const float |
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| 61 | #else |
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| 62 | static float |
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| 63 | #endif |
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| 64 | one = 1.0, |
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| 65 | huge = 1.0e30; |
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| 66 | |||
| 67 | #ifdef __STDC__ |
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| 68 | float atanf(float x) |
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| 69 | #else |
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| 70 | float atanf(x) |
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| 71 | float x; |
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| 72 | #endif |
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| 73 | { |
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| 74 | float w,s1,s2,z; |
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| 75 | __int32_t ix,hx,id; |
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| 76 | |||
| 77 | GET_FLOAT_WORD(hx,x); |
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| 78 | ix = hx&0x7fffffff; |
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| 79 | if(ix>=0x50800000) { /* if |x| >= 2^34 */ |
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| 80 | if(FLT_UWORD_IS_NAN(ix)) |
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| 81 | return x+x; /* NaN */ |
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| 82 | if(hx>0) return atanhi[3]+atanlo[3]; |
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| 83 | else return -atanhi[3]-atanlo[3]; |
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| 84 | } if (ix < 0x3ee00000) { /* |x| < 0.4375 */ |
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| 85 | if (ix < 0x31000000) { /* |x| < 2^-29 */ |
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| 86 | if(huge+x>one) return x; /* raise inexact */ |
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| 87 | } |
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| 88 | id = -1; |
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| 89 | } else { |
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| 90 | x = fabsf(x); |
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| 91 | if (ix < 0x3f980000) { /* |x| < 1.1875 */ |
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| 92 | if (ix < 0x3f300000) { /* 7/16 <=|x|<11/16 */ |
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| 93 | id = 0; x = ((float)2.0*x-one)/((float)2.0+x); |
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| 94 | } else { /* 11/16<=|x|< 19/16 */ |
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| 95 | id = 1; x = (x-one)/(x+one); |
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| 96 | } |
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| 97 | } else { |
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| 98 | if (ix < 0x401c0000) { /* |x| < 2.4375 */ |
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| 99 | id = 2; x = (x-(float)1.5)/(one+(float)1.5*x); |
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| 100 | } else { /* 2.4375 <= |x| < 2^66 */ |
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| 101 | id = 3; x = -(float)1.0/x; |
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| 102 | } |
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| 103 | }} |
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| 104 | /* end of argument reduction */ |
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| 105 | z = x*x; |
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| 106 | w = z*z; |
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| 107 | /* break sum from i=0 to 10 aT[i]z**(i+1) into odd and even poly */ |
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| 108 | s1 = z*(aT[0]+w*(aT[2]+w*(aT[4]+w*(aT[6]+w*(aT[8]+w*aT[10]))))); |
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| 109 | s2 = w*(aT[1]+w*(aT[3]+w*(aT[5]+w*(aT[7]+w*aT[9])))); |
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| 110 | if (id<0) return x - x*(s1+s2); |
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| 111 | else { |
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| 112 | z = atanhi[id] - ((x*(s1+s2) - atanlo[id]) - x); |
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| 113 | return (hx<0)? -z:z; |
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| 114 | } |
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| 115 | } |
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| 116 | |||
| 117 | #ifdef _DOUBLE_IS_32BITS |
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| 118 | |||
| 119 | #ifdef __STDC__ |
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| 120 | double atan(double x) |
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| 121 | #else |
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| 122 | double atan(x) |
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| 123 | double x; |
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| 124 | #endif |
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| 125 | { |
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| 126 | return (double) atanf((float) x); |
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| 127 | } |
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| 128 | |||
| 129 | #endif /* defined(_DOUBLE_IS_32BITS) */ |