xhunt.c

< C语言数值算法程序大全>>配套程序

/* Driver for routine hunt */

#include <stdio.h>
#include <math.h>
#include "nr.h"
#include "nrutil.h"

#define N 100

main()
{
	unsigned long i,j,ji;
	float x,*xx;

	xx=vector(1,N);
	/* create array to be searched */
	for (i=1;i<=N;i++)
		xx[i]=exp(i/20.0)-74.0;
	printf("\n  result of:   j=0 indicates x too small\n");
	printf("%14s j=100 indicates x too large"," ");
	printf("\n%12s %8s %4s %11s %13s \n",
		"locate:","guess","j","xx(j)","xx(j+1)");
	/* do test */
	for (i=1;i<=19;i++) {
		x = -100.0+10.0*i;
		/* trial parameter */
		j=(ji=5*i);
		/* begin search */
		hunt(xx,N,x,&j);
		if ((j < N) && (j > 0))
			printf("%12.5f %6lu %6lu %12.6f %12.6f \n",
				x,ji,j,xx[j],xx[j+1]);
		else if (j == N)
			printf("%12.5f %6lu %6lu %12.6f %s \n",
				x,ji,j,xx[j],"   upper lim");
		else
			printf("%12.5f %6lu %6lu %s %12.6f \n",
				x,ji,j,"   lower lim",xx[j+1]);
	}
	free_vector(xx,1,N);
	return 0;
}