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| Rev | Author | Line No. | Line |
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| 3362 | Serge | 1 | |
| 2 | /* |
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| 3 | * ==================================================== |
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| 4 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
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| 5 | * |
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| 6 | * Developed at SunPro, a Sun Microsystems, Inc. business. |
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| 7 | * Permission to use, copy, modify, and distribute this |
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| 8 | * software is freely granted, provided that this notice |
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| 9 | * is preserved. |
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| 10 | * ==================================================== |
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| 11 | */ |
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| 12 | |||
| 13 | |||
| 14 | |||
| 15 | |||
| 16 | < |
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| 17 | |||
| 18 | |||
| 19 | tanh |
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| 20 | INDEX |
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| 21 | tanhf |
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| 22 | |||
| 23 | |||
| 24 | #include |
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| 25 | double tanh(double <[x]>); |
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| 26 | float tanhf(float <[x]>); |
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| 27 | |||
| 28 | |||
| 29 | #include |
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| 30 | double tanh(<[x]>) |
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| 31 | double <[x]>; |
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| 32 | |||
| 33 | |||
| 34 | float <[x]>; |
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| 35 | |||
| 36 | |||
| 37 | |||
| 38 | |||
| 39 | |||
| 40 | the argument <[x]>. Angles are specified in radians. |
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| 41 | |||
| 42 | |||
| 43 | . sinh(<[x]>)/cosh(<[x]>) |
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| 44 | |||
| 45 | |||
| 46 | |||
| 47 | |||
| 48 | The hyperbolic tangent of <[x]> is returned. |
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| 49 | |||
| 50 | |||
| 51 | < |
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| 52 | |||
| 53 | |||
| 54 | |||
| 55 | |||
| 56 | * Return the Hyperbolic Tangent of x |
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| 57 | * |
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| 58 | * Method : |
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| 59 | * x -x |
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| 60 | * e - e |
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| 61 | * 0. tanh(x) is defined to be ----------- |
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| 62 | * x -x |
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| 63 | * e + e |
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| 64 | * 1. reduce x to non-negative by tanh(-x) = -tanh(x). |
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| 65 | * 2. 0 <= x <= 2**-55 : tanh(x) := x*(one+x) |
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| 66 | * -t |
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| 67 | * 2**-55 < x <= 1 : tanh(x) := -----; t = expm1(-2x) |
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| 68 | * t + 2 |
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| 69 | * 2 |
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| 70 | * 1 <= x <= 22.0 : tanh(x) := 1- ----- ; t=expm1(2x) |
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| 71 | * t + 2 |
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| 72 | * 22.0 < x <= INF : tanh(x) := 1. |
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| 73 | * |
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| 74 | * Special cases: |
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| 75 | * tanh(NaN) is NaN; |
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| 76 | * only tanh(0)=0 is exact for finite argument. |
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| 77 | */ |
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| 78 | |||
| 79 | |||
| 80 | |||
| 81 | |||
| 82 | |||
| 83 | |||
| 84 | static const double one=1.0, two=2.0, tiny = 1.0e-300; |
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| 85 | #else |
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| 86 | static double one=1.0, two=2.0, tiny = 1.0e-300; |
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| 87 | #endif |
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| 88 | |||
| 89 | |||
| 90 | double tanh(double x) |
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| 91 | #else |
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| 92 | double tanh(x) |
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| 93 | double x; |
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| 94 | #endif |
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| 95 | { |
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| 96 | double t,z; |
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| 97 | __int32_t jx,ix; |
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| 98 | |||
| 99 | |||
| 100 | GET_HIGH_WORD(jx,x); |
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| 101 | ix = jx&0x7fffffff; |
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| 102 | |||
| 103 | |||
| 104 | if(ix>=0x7ff00000) { |
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| 105 | if (jx>=0) return one/x+one; /* tanh(+-inf)=+-1 */ |
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| 106 | else return one/x-one; /* tanh(NaN) = NaN */ |
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| 107 | } |
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| 108 | |||
| 109 | |||
| 110 | if (ix < 0x40360000) { /* |x|<22 */ |
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| 111 | if (ix<0x3c800000) /* |x|<2**-55 */ |
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| 112 | return x*(one+x); /* tanh(small) = small */ |
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| 113 | if (ix>=0x3ff00000) { /* |x|>=1 */ |
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| 114 | t = expm1(two*fabs(x)); |
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| 115 | z = one - two/(t+two); |
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| 116 | } else { |
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| 117 | t = expm1(-two*fabs(x)); |
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| 118 | z= -t/(t+two); |
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| 119 | } |
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| 120 | /* |x| > 22, return +-1 */ |
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| 121 | } else { |
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| 122 | z = one - tiny; /* raised inexact flag */ |
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| 123 | } |
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| 124 | return (jx>=0)? z: -z; |
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| 125 | } |
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| 126 | |||
| 127 | |||
| 128 |