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[/] [or1k/] [trunk/] [linux/] [uClibc/] [libm/] [w_jn.c] - Blame information for rev 1765

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1 1325 phoenix
/* @(#)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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#if defined(LIBM_SCCS) && !defined(lint)
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static char rcsid[] = "$NetBSD: w_jn.c,v 1.6 1995/05/10 20:49:19 jtc 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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#ifdef __STDC__
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        double jn(int n, double x)      /* wrapper jn */
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#else
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        double jn(n,x)                  /* wrapper jn */
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        double x; int n;
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#endif
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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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#ifdef __STDC__
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        double yn(int n, double x)      /* wrapper yn */
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#else
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        double yn(n,x)                  /* wrapper yn */
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        double x; int n;
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#endif
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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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