xsimpr.c

Numerical Recipes in C的源代码

/* Driver for routine simpr */

#include <stdio.h>
#define NRANSI
#include "nr.h"
#include "nrutil.h"

#define NVAR 3
#define X1 0.0
#define HTOT 50.0

int main(void)
{
	int i;
	float a1=0.5976,a2=1.4023,a3=0.0,*y,*yout,*dfdx,**dfdy,*dydx;

	y=vector(1,NVAR);
	yout=vector(1,NVAR);
	dfdx=vector(1,NVAR);
	dfdy=matrix(1,NVAR,1,NVAR);
	dydx=vector(1,NVAR);
	y[1]=y[2]=1.0;
	y[3]=0.0;
	derivs(X1,y,dydx);
	jacobn(X1,y,dfdx,dfdy,NVAR);
	printf("Test Problem:\n");
	for (i=5;i<=50;i+=5) {
		simpr(y,dydx,dfdx,dfdy,NVAR,X1,HTOT,i,yout,derivs);
		printf("\n%s %5.2f %s %5.2f %s %2d %s \n",
			"x=",X1," to ",X1+HTOT," in ",i," steps");
		printf("%14s %9s\n","integration","bessj");
		printf("%12.6f %12.6f\n",yout[1],a1);
		printf("%12.6f %12.6f\n",yout[2],a2);
		printf("%12.6f %12.6f\n",yout[3],a3);
	}
	free_vector(dydx,1,NVAR);
	free_matrix(dfdy,1,NVAR,1,NVAR);
	free_vector(dfdx,1,NVAR);
	free_vector(yout,1,NVAR);
	free_vector(y,1,NVAR);
	return 0;
}
#undef NRANSI