5980be9b3c
This work is based in part on code from NetBSD libm, libc and kernel. The library is partly public domain and partly BSD-style licensed.
86 lines
2.3 KiB
C
86 lines
2.3 KiB
C
/* @(#)w_jn.c 5.1 93/09/24 */
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/*
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* ====================================================
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* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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*
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* Developed at SunPro, a Sun Microsystems, Inc. business.
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* Permission to use, copy, modify, and distribute this
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* software is freely granted, provided that this notice
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* is preserved.
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* ====================================================
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*/
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#include <sys/cdefs.h>
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#if defined(LIBM_SCCS) && !defined(lint)
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__RCSID("$NetBSD: w_jn.c,v 1.9 2002/05/26 22:02:01 wiz Exp $");
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#endif
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/*
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* wrapper jn(int n, double x), yn(int n, double x)
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* floating point Bessel's function of the 1st and 2nd kind
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* of order n
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*
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* Special cases:
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* y0(0)=y1(0)=yn(n,0) = -inf with division by zero signal;
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* y0(-ve)=y1(-ve)=yn(n,-ve) are NaN with invalid signal.
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* Note 2. About jn(n,x), yn(n,x)
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* For n=0, j0(x) is called,
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* for n=1, j1(x) is called,
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* for n<x, forward recursion us used starting
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* from values of j0(x) and j1(x).
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* for n>x, a continued fraction approximation to
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* j(n,x)/j(n-1,x) is evaluated and then backward
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* recursion is used starting from a supposed value
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* for j(n,x). The resulting value of j(0,x) is
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* compared with the actual value to correct the
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* supposed value of j(n,x).
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*
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* yn(n,x) is similar in all respects, except
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* that forward recursion is used for all
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* values of n>1.
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*
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*/
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#include "math.h"
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#include "math_private.h"
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double
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jn(int n, double x) /* wrapper jn */
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{
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#ifdef _IEEE_LIBM
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return __ieee754_jn(n,x);
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#else
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double z;
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z = __ieee754_jn(n,x);
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if(_LIB_VERSION == _IEEE_ || isnan(x) ) return z;
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if(fabs(x)>X_TLOSS) {
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return __kernel_standard((double)n,x,38); /* jn(|x|>X_TLOSS,n) */
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} else
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return z;
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#endif
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}
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double
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yn(int n, double x) /* wrapper yn */
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{
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#ifdef _IEEE_LIBM
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return __ieee754_yn(n,x);
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#else
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double z;
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z = __ieee754_yn(n,x);
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if(_LIB_VERSION == _IEEE_ || isnan(x) ) return z;
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if(x <= 0.0){
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if(x==0.0)
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/* d= -one/(x-x); */
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return __kernel_standard((double)n,x,12);
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else
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/* d = zero/(x-x); */
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return __kernel_standard((double)n,x,13);
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}
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if(x>X_TLOSS) {
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return __kernel_standard((double)n,x,39); /* yn(x>X_TLOSS,n) */
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} else
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return z;
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#endif
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}
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