xqroot.c

Numerical Recipes in C的源代码

/* Driver for routine qroot */

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

#define N 6 /* degree of polynomial */
#define EPS 1.0e-6
#define NTRY 10
#define TINY 1.0e-5

int main(void)
{
	int i,j,nflag,nroot=0;
	static float p[N+1]={10.0,-18.0,25.0,-24.0,16.0,-6.0,1.0};
	float *b,*c;

	b=vector(1,NTRY);
	c=vector(1,NTRY);
	printf("\nP(x)=x^6-6x^5+16x^4-24x^3+25x^2-18x+10\n");
	printf("Quadratic factors x^2+bx+c\n\n");
	printf("%6s %10s %12s \n\n","factor","b","c");
	for (i=1;i<=NTRY;i++) {
		c[i]=0.5*i;
		b[i] = -0.5*i;
		qroot(p,N,&b[i],&c[i],EPS);
		if (nroot == 0) {
			printf("%4d %15.6f %12.6f\n",nroot,b[i],c[i]);
			nroot=1;
		} else {
			nflag=0;
			for (j=1;j<=nroot;j++)
				if ((fabs(b[i]-b[j]) < TINY)
					&& (fabs(c[i]-c[j]) < TINY))
					nflag=1;
			if (nflag == 0) {
				printf("%4d %15.6f %12.6f\n",nroot,b[i],c[i]);
				++nroot;
			}
		}
	}
	free_vector(c,1,NTRY);
	free_vector(b,1,NTRY);
	return 0;
}
#undef NRANSI