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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