| 1 | /* sf_tanh.c -- float version of s_tanh.c. |
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| 2 | * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com. |
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| 3 | */ |
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| 4 | |
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| 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 | #include "fdlibm.h" |
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| 17 | |
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| 18 | #ifdef __STDC__ |
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| 19 | static const float one=1.0, two=2.0, tiny = 1.0e-30; |
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| 20 | #else |
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| 21 | static float one=1.0, two=2.0, tiny = 1.0e-30; |
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| 22 | #endif |
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| 23 | |
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| 24 | #ifdef __STDC__ |
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| 25 | float tanhf(float x) |
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| 26 | #else |
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| 27 | float tanhf(x) |
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| 28 | float x; |
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| 29 | #endif |
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| 30 | { |
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| 31 | float t,z; |
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| 32 | __int32_t jx,ix; |
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| 33 | |
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| 34 | GET_FLOAT_WORD(jx,x); |
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| 35 | ix = jx&0x7fffffff; |
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| 36 | |
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| 37 | /* x is INF or NaN */ |
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| 38 | if(!FLT_UWORD_IS_FINITE(ix)) { |
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| 39 | if (jx>=0) return one/x+one; /* tanh(+-inf)=+-1 */ |
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| 40 | else return one/x-one; /* tanh(NaN) = NaN */ |
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| 41 | } |
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| 42 | |
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| 43 | /* |x| < 22 */ |
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| 44 | if (ix < 0x41b00000) { /* |x|<22 */ |
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| 45 | if (ix<0x24000000) /* |x|<2**-55 */ |
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| 46 | return x*(one+x); /* tanh(small) = small */ |
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| 47 | if (ix>=0x3f800000) { /* |x|>=1 */ |
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| 48 | t = expm1f(two*fabsf(x)); |
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| 49 | z = one - two/(t+two); |
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| 50 | } else { |
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| 51 | t = expm1f(-two*fabsf(x)); |
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| 52 | z= -t/(t+two); |
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| 53 | } |
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| 54 | /* |x| > 22, return +-1 */ |
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| 55 | } else { |
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| 56 | z = one - tiny; /* raised inexact flag */ |
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| 57 | } |
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| 58 | return (jx>=0)? z: -z; |
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| 59 | } |
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| 60 | |
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| 61 | #ifdef _DOUBLE_IS_32BITS |
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| 62 | |
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| 63 | #ifdef __STDC__ |
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| 64 | double tanh(double x) |
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| 65 | #else |
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| 66 | double tanh(x) |
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| 67 | double x; |
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| 68 | #endif |
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| 69 | { |
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| 70 | return (double) tanhf((float) x); |
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| 71 | } |
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| 72 | |
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| 73 | #endif /* defined(_DOUBLE_IS_32BITS) */ |
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