| 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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