56 lines
1.0 KiB
C
56 lines
1.0 KiB
C
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/* Driver for routine rkqs */
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#include <stdio.h>
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#include <math.h>
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#define NRANSI
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#include "nr.h"
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#include "nrutil.h"
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#define N 4
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void derivs(float x,float y[],float dydx[])
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{
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dydx[1] = -y[2];
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dydx[2]=y[1]-(1.0/x)*y[2];
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dydx[3]=y[2]-(2.0/x)*y[3];
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dydx[4]=y[3]-(3.0/x)*y[4];
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}
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int main(void)
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{
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int i,j;
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float eps,hdid,hnext,htry,x=1.0,*y,*dydx,*dysav,*ysav,*yscal;
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y=vector(1,N);
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dydx=vector(1,N);
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dysav=vector(1,N);
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ysav=vector(1,N);
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yscal=vector(1,N);
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ysav[1]=bessj0(x);
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ysav[2]=bessj1(x);
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ysav[3]=bessj(2,x);
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ysav[4]=bessj(3,x);
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derivs(x,ysav,dysav);
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for (i=1;i<=N;i++) yscal[i]=1.0;
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htry=0.6;
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printf("%10s %11s %12s %13s\n","eps","htry","hdid","hnext");
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for (i=1;i<=15;i++) {
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eps=exp((double) -i);
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x=1.0;
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for (j=1;j<=N;j++) {
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y[j]=ysav[j];
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dydx[j]=dysav[j];
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}
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rkqs(y,dydx,N,&x,htry,eps,yscal,&hdid,&hnext,derivs);
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printf("%13f %8.2f %14.6f %12.6f \n",eps,htry,hdid,hnext);
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}
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free_vector(yscal,1,N);
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free_vector(ysav,1,N);
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free_vector(dysav,1,N);
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free_vector(dydx,1,N);
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free_vector(y,1,N);
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return 0;
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}
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#undef NRANSI
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