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| Rev | Author | Line No. | Line |
|---|---|---|---|
| 2 | pj | 1 | /* s_tanhf.c -- float version of s_tanh.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 | |||
| 16 | #ifndef lint |
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| 17 | static char rcsid[] = "$\Id: s_tanhf.c,v 1.2 1995/05/30 05:50:36 rgrimes Exp $"; |
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| 18 | #endif |
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| 19 | |||
| 20 | #include "math.h" |
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| 21 | #include "math_private.h" |
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| 22 | |||
| 23 | #ifdef __STDC__ |
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| 24 | static const float one=1.0, two=2.0, tiny = 1.0e-30; |
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| 25 | #else |
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| 26 | static float one=1.0, two=2.0, tiny = 1.0e-30; |
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| 27 | #endif |
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| 28 | |||
| 29 | #ifdef __STDC__ |
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| 30 | float tanhf(float x) |
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| 31 | #else |
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| 32 | float tanhf(x) |
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| 33 | float x; |
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| 34 | #endif |
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| 35 | { |
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| 36 | float t,z; |
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| 37 | int32_t jx,ix; |
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| 38 | |||
| 39 | GET_FLOAT_WORD(jx,x); |
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| 40 | ix = jx&0x7fffffff; |
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| 41 | |||
| 42 | /* x is INF or NaN */ |
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| 43 | if(ix>=0x7f800000) { |
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| 44 | if (jx>=0) return one/x+one; /* tanh(+-inf)=+-1 */ |
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| 45 | else return one/x-one; /* tanh(NaN) = NaN */ |
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| 46 | } |
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| 47 | |||
| 48 | /* |x| < 22 */ |
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| 49 | if (ix < 0x41b00000) { /* |x|<22 */ |
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| 50 | if (ix<0x24000000) /* |x|<2**-55 */ |
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| 51 | return x*(one+x); /* tanh(small) = small */ |
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| 52 | if (ix>=0x3f800000) { /* |x|>=1 */ |
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| 53 | t = expm1f(two*fabsf(x)); |
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| 54 | z = one - two/(t+two); |
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| 55 | } else { |
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| 56 | t = expm1f(-two*fabsf(x)); |
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| 57 | z= -t/(t+two); |
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| 58 | } |
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| 59 | /* |x| > 22, return +-1 */ |
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| 60 | } else { |
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| 61 | z = one - tiny; /* raised inexact flag */ |
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| 62 | } |
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| 63 | return (jx>=0)? z: -z; |
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| 64 | } |