3a8617a83f
-- Begin comments from J.T. Conklin: The most significant improvement is the addition of "float" versions of the math functions that take float arguments, return floats, and do all operations in floating point. This doesn't help (performance) much on the i386, but they are still nice to have. The float versions were orginally done by Cygnus' Ian Taylor when fdlibm was integrated into the libm we support for embedded systems. I gave Ian a copy of my libm as a starting point since I had already fixed a lot of bugs & problems in Sun's original code. After he was done, I cleaned it up a bit and integrated the changes back into my libm. -- End comments Reviewed by: jkh Submitted by: jtc
93 lines
2.4 KiB
C
93 lines
2.4 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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#ifndef lint
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static char rcsid[] = "$Id: w_jn.c,v 1.4 1994/08/10 20:34:42 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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