1 | |
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2 | /* @(#)w_jn.c 5.1 93/09/24 */ |
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3 | /* |
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4 | * ==================================================== |
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5 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
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6 | * |
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7 | * Developed at SunPro, a Sun Microsystems, Inc. business. |
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8 | * Permission to use, copy, modify, and distribute this |
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9 | * software is freely granted, provided that this notice |
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10 | * is preserved. |
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11 | * ==================================================== |
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12 | */ |
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13 | |
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14 | /* |
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15 | * wrapper jn(int n, double x), yn(int n, double x) |
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16 | * floating point Bessel's function of the 1st and 2nd kind |
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17 | * of order n |
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18 | * |
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19 | * Special cases: |
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20 | * y0(0)=y1(0)=yn(n,0) = -inf with division by zero signal; |
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21 | * y0(-ve)=y1(-ve)=yn(n,-ve) are NaN with invalid signal. |
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22 | * Note 2. About jn(n,x), yn(n,x) |
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23 | * For n=0, j0(x) is called, |
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24 | * for n=1, j1(x) is called, |
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25 | * for n<x, forward recursion us used starting |
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26 | * from values of j0(x) and j1(x). |
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27 | * for n>x, a continued fraction approximation to |
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28 | * j(n,x)/j(n-1,x) is evaluated and then backward |
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29 | * recursion is used starting from a supposed value |
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30 | * for j(n,x). The resulting value of j(0,x) is |
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31 | * compared with the actual value to correct the |
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32 | * supposed value of j(n,x). |
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33 | * |
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34 | * yn(n,x) is similar in all respects, except |
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35 | * that forward recursion is used for all |
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36 | * values of n>1. |
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37 | * |
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38 | */ |
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39 | |
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40 | #include <libm/fdlibm.h> |
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41 | |
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42 | #ifdef __STDC__ |
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43 | double jn(int n, double x) /* wrapper jn */ |
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44 | #else |
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45 | double jn(n,x) /* wrapper jn */ |
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46 | double x; int n; |
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47 | #endif |
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48 | { |
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49 | #ifdef _IEEE_LIBM |
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50 | return __ieee754_jn(n,x); |
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51 | #else |
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52 | double z; |
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53 | z = __ieee754_jn(n,x); |
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54 | if(_LIB_VERSION == _IEEE_ || isnan(x) ) return z; |
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55 | if(fabs(x)>X_TLOSS) { |
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56 | return __kernel_standard((double)n,x,38); /* jn(|x|>X_TLOSS,n) */ |
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57 | } else |
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58 | return z; |
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59 | #endif |
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60 | } |
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61 | |
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62 | #ifdef __STDC__ |
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63 | double yn(int n, double x) /* wrapper yn */ |
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64 | #else |
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65 | double yn(n,x) /* wrapper yn */ |
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66 | double x; int n; |
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67 | #endif |
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68 | { |
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69 | #ifdef _IEEE_LIBM |
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70 | return __ieee754_yn(n,x); |
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71 | #else |
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72 | double z; |
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73 | z = __ieee754_yn(n,x); |
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74 | if(_LIB_VERSION == _IEEE_ || isnan(x) ) return z; |
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75 | if(x <= 0.0){ |
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76 | if(x==0.0) |
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77 | /* d= -one/(x-x); */ |
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78 | return __kernel_standard((double)n,x,12); |
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79 | else |
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80 | /* d = zero/(x-x); */ |
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81 | return __kernel_standard((double)n,x,13); |
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82 | } |
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83 | if(x>X_TLOSS) { |
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84 | return __kernel_standard((double)n,x,39); /* yn(x>X_TLOSS,n) */ |
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85 | } else |
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86 | return z; |
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87 | #endif |
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88 | } |
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