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/* Copyright (C) 2017 - IIT Bombay - FOSSEE
This file must be used under the terms of the CeCILL.
This source file is licensed as described in the file COPYING, which
you should have received as part of this distribution. The terms
are also available at
http://www.cecill.info/licences/Licence_CeCILL_V2-en.txt
Organization: FOSSEE, IIT Bombay
Author: Brijesh Gupta C R
Email: toolbox@scilab.in
*/
#include <stdio.h>
#include "math.h"
#include "besselj.h"
#define ACC 40.0
#define BIGNO 1.0e10
#define BIGNI 1.0e-10
static double bessj0( double x )
{
double ax,z;
double xx,y,ans,ans1,ans2;
if ((ax=fabs(x)) < 8.0) {
y=x*x;
ans1=57568490574.0+y*(-13362590354.0+y*(651619640.7
+y*(-11214424.18+y*(77392.33017+y*(-184.9052456)))));
ans2=57568490411.0+y*(1029532985.0+y*(9494680.718
+y*(59272.64853+y*(267.8532712+y*1.0))));
ans=ans1/ans2;
} else {
z=8.0/ax;
y=z*z;
xx=ax-0.785398164;
ans1=1.0+y*(-0.1098628627e-2+y*(0.2734510407e-4
+y*(-0.2073370639e-5+y*0.2093887211e-6)));
ans2 = -0.1562499995e-1+y*(0.1430488765e-3
+y*(-0.6911147651e-5+y*(0.7621095161e-6
-y*0.934935152e-7)));
ans=sqrt(0.636619772/ax)*(cos(xx)*ans1-z*sin(xx)*ans2);
}
return ans;
}
static double bessj1( double x )
{
double ax,z;
double xx,y,ans,ans1,ans2;
if ((ax=fabs(x)) < 8.0) {
y=x*x;
ans1=x*(72362614232.0+y*(-7895059235.0+y*(242396853.1
+y*(-2972611.439+y*(15704.48260+y*(-30.16036606))))));
ans2=144725228442.0+y*(2300535178.0+y*(18583304.74
+y*(99447.43394+y*(376.9991397+y*1.0))));
ans=ans1/ans2;
} else {
z=8.0/ax;
y=z*z;
xx=ax-2.356194491;
ans1=1.0+y*(0.183105e-2+y*(-0.3516396496e-4
+y*(0.2457520174e-5+y*(-0.240337019e-6))));
ans2=0.04687499995+y*(-0.2002690873e-3
+y*(0.8449199096e-5+y*(-0.88228987e-6
+y*0.105787412e-6)));
ans=sqrt(0.636619772/ax)*(cos(xx)*ans1-z*sin(xx)*ans2);
if (x < 0.0) ans = -ans;
}
return ans;
}
double bessj( int n, double x )
{
int j, jsum, m;
double ax, bj, bjm, bjp, sum, tox, ans;
if (n < 0)
{
double dblank;
//setdblack_c( &dblank );
return( dblank );
}
ax=fabs(x);
if (n == 0)
return( bessj0(ax) );
if (n == 1)
return( bessj1(ax) );
if (ax == 0.0)
return 0.0;
else if (ax > (double) n) {
tox=2.0/ax;
bjm=bessj0(ax);
bj=bessj1(ax);
for (j=1;j<n;j++) {
bjp=j*tox*bj-bjm;
bjm=bj;
bj=bjp;
}
ans=bj;
} else {
tox=2.0/ax;
m=2*((n+(int) sqrt(ACC*n))/2);
jsum=0;
bjp=ans=sum=0.0;
bj=1.0;
for (j=m;j>0;j--) {
bjm=j*tox*bj-bjp;
bjp=bj;
bj=bjm;
if (fabs(bj) > BIGNO) {
bj *= BIGNI;
bjp *= BIGNI;
ans *= BIGNI;
sum *= BIGNI;
}
if (jsum) sum += bj;
jsum=!jsum;
if (j == n) ans=bjp;
}
sum=2.0*sum-bj;
ans /= sum;
}
return x < 0.0 && n%2 == 1 ? -ans : ans;
}
void dbesselja(double* inp1,int size1, double* inp2,int size2, double* oup)
{
int i;
if(size1 != size2)
printf("Error! arguments #1 and #2 have incompatible dimensions.");
for(i = 0; i<size1;i++)
{
oup[i] = bessj(inp1[i],inp2[i]);
}
}
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